DIYstompboxes.com

Hello everyone

Yes I know I should be fixing that amplifier first, (I'm working on it) but at the moment I've managed to damage one of my knees* and I'm on pain killers and I don't trust my somewhat medicated brain around a 240V circuit that I already shocked myself on once while sober, so I thought, aha, let's work on something easy and 9V instead! That way I can't hurt myself when the circuit invariably goes wrong...

I found a layout a few months ago posted by the chap who runs Leyland Pedals and he called it the Ultra Simple Tremolo, and it has very few parts and I thought I'd build that (I'd also like to rebuild some confidence; I have only built three pedals in the last 12 months and none have worked). His layout is below:

(https://i.imgur.com/pXLZPkv.png)

So I've laid this out in DIYLC on vero and I wanted to check if it is right before I build it - I'm not sure if I've drawn the two 10uF capacitors the right way round. I think the rest of the circuit is correct....

(https://i.imgur.com/4OSDe1O.png)


Now if the above works, then I was thinking... this circuit uses a dual op amp, one amp of which is doing nothing... and tremolos often appear to suffer from a drop in (perceived) volume, so could I use the other remaining op amp as a boost? So the below schematic is my guess at how to do this (using U1A of the TL072 as the boost). I'm not sure what value capacitor to put on it, or what value the pot should be, or even if this would work, but it would be lovely to hear anyone's suggestions.

(https://i.imgur.com/pT3E7vx.png)

Hope your Summer is going well!


*just because you can repair some damage to your roof for free, doesn't mean it's always a good idea to do it yourself :(

A couple of things  it's a good idea to at least add a series resistor like the Dallas Arbiter Tremolo,

https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/

The transistor needs to work as part of a voltage divider.  In the Leyand it's relying on the pickup providing the impedance but it's not going to work well if you place buffered output pedals before it.

As far as your gain restoring circuit goes it needs work.   In short just take any non-inverting opamp circuit and put it after the tremollo,

https://www.electrosmash.com/mxr-microamp

No doubt you can strip it back a bit.

The main issues with your schematic are:
- The opamp connection has a lot of issues since you are DC coupling the input.
- The inverting scheme doesn't lend itself to the best solution.   (It is possible to do a inverting version
   but it will be less optimal than the non-inverting.)
- You are taking the 4.5V/Vref line from the oscillator circuit.
   It looks like a 4.5V/Vref, and it kind of is, but it's not a Vref suitable to connect to audio.
   That 4.5V/Vref is part of the oscillator circuit and works in conjunction with the 220k
   resistor feeding back to the opamp + input.   The voltage at that point is varying
   if you use it for audio it will tick.   You can't even add a cap across that Vref to fix it
   since it will stop the oscillator.

If you look at the Schaller Tremolo you can see a similar kind of idea which uses a BJT
amplifier to restore the level.   It's both similar and different.  The colorsound is another one.
IIRC the DIAZ Tremodillo was a another  transistor based tremolo.

You can stick to your plan using an opamp.

Quote from: Rob Strand on August 16, 2022, 06:21:37 PM
A couple of things  it's a good idea to at least add a series resistor like the Dallas Arbiter Tremolo,

https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/

The transistor needs to work as part of a voltage divider.  In the Leyand it's relying on the pickup providing the impedance but it's not going to work well if you place buffered output pedals before it.

Thanks Rob! I had a lok at that schematic and I was not sure what the series resistor was - from comparing the Leyland with the Dallas, my guess is that it is the 10K on the Dallas that is after the audio in - I've added it below and labelled it 10K series... but then I saw you say it needs to be a voltage divider, so would that mean the resistor needs to move to the right (past the junction with the 2n5088?) and also should it be the same value as the 1M resistor that goes to ground after the audio input ( I am assuming that would be the second resistor in the voltage divider? I think a voltage divider need two equal value resistors?). In short, I'm not sure (sorry!)

(https://i.imgur.com/a4bYmYj.png)

Quote from: Rob Strand on August 16, 2022, 06:21:37 PM
As far as your gain restoring circuit goes it needs work.   In short just take any non-inverting opamp circuit and put it after the tremollo,

https://www.electrosmash.com/mxr-microamp

No doubt you can strip it back a bit.

The main issues with your schematic are:
- The opamp connection has a lot of issues since you are DC coupling the input.
- The inverting scheme doesn't lend itself to the best solution.   (It is possible to do a inverting version
   but it will be less optimal than the non-inverting.)
- You are taking the 4.5V/Vref line from the oscillator circuit.
   It looks like a 4.5V/Vref, and it kind of is, but it's not a Vref suitable to connect to audio.
   That 4.5V/Vref is part of the oscillator circuit and works in conjunction with the 220k
   resistor feeding back to the opamp + input.   The voltage at that point is varying
   if you use it for audio it will tick.   You can't even add a cap across that Vref to fix it
   since it will stop the oscillator.

If you look at the Schaller Tremolo you can see a similar kind of idea which uses a BJT
amplifier to restore the level.   It's both similar and different.  The colorsound is another one.
IIRC the DIAZ Tremodillo was a another  transistor based tremolo.

You can stick to your plan using an opamp.

thanks again - that looks a lot more complicated than I envisaged... I presume this is due to the IC involved? Or maybe I can remove a lot of the components? I built a very loud clean booster using an LM386 chip last year that was very simple and had only a fraction of the amount of components that the MXR microamp has...

(https://i.imgur.com/4OSDe1O.png)

moidy old bean - you very need to add power supply connections to the IC - ground to pin 4 and supply to pin 8. and we NEVER leave an unattended opamp like that, even if we aren't using it, we properly terminate it.

see if you can find a copy of the vicovibe circuit diagram - it's actually a trem.

summer? when?

Quote from: moid on August 17, 2022, 09:12:57 AM
(https://i.imgur.com/a4bYmYj.png)

That's looking a bit better. The 10K works with the transistor acting as the lower resistor to make a voltage divider. When the transistor is off, the lower part of the divider is a very high resistance and virtually all of the signal goes through. When the transistor is on, the lower part of the divider is a very low resistance, and only a fraction of the signal goes through. Hence, the magic of volume control and tremolo!!

I did a similar thing recently with a vactrol. In fact, there's quite a lot of this that is similar, so you should take a look:

https://electricdruid.net/two-stomplfo-projects-mini-tremolo/ (https://electricdruid.net/two-stomplfo-projects-mini-tremolo/)

You could directly lift the buffer-with-gain I used at the input to fix your volume issue:

(https://electricdruid.net/wp-content/uploads/2022/08/InputStage-1.jpg)

I think you'd been thinking of putting the boost after, but it could go before instead. Or drop R2/R3/R4/C5 (the usual input components) and stick it after.
Duck's right though, you need to do *something* with that other op-amp. You can't leave it floating about like that. Not good practice.

HTH,
Tom

Quote from: duck_arse on August 17, 2022, 11:35:45 AM
(https://i.imgur.com/4OSDe1O.png)

moidy old bean - you very need to add power supply connections to the IC - ground to pin 4 and supply to pin 8. and we NEVER leave an unattended opamp like that, even if we aren't using it, we properly terminate it.

see if you can find a copy of the vicovibe circuit diagram - it's actually a trem.

summer? when?

Thanks Duck, long time no quack! I did wonder about that - I was thinking how does this opamp work without power, and then I thought, well the power is coming in through pin 5 and the op amp isn't being used to amplify audio so maybe it doesn't matter... but it obviously does and the original schematic doesn't tell me this (presumably because it's so basic!). I will re draw the schematic and layout as soon as I am more lucid.

I will search for the vicovibe - I found a thread about it on TheOtherPlace... but there are multiple versions of the schematic there. I think this one is the circuit without any mods?
(https://i.imgur.com/IJqTxBp.png)

From the demos I've heard it sounds nice, but the people on the other forum reported a lot of issues with getting it to work.... was there something specific to look at on it? I did find one suggestion for adding a rate LED that I might try to see if it works with this circuit
(https://www.freestompboxes.org/download/file.php?id=18110)

Quote from: ElectricDruid on August 17, 2022, 01:26:41 PM

That's looking a bit better. The 10K works with the transistor acting as the lower resistor to make a voltage divider. When the transistor is off, the lower part of the divider is a very high resistance and virtually all of the signal goes through. When the transistor is on, the lower part of the divider is a very low resistance, and only a fraction of the signal goes through. Hence, the magic of volume control and tremolo!!

Thanks Tom! So I put it in the right place, but for the wrong reason? Sounds like the story of my life! I was thinking that the 1M and the 10K were the voltage divider, never thought to consider that the 2n5088 connects to ground as well.

Quote from: ElectricDruid on August 17, 2022, 01:26:41 PM
I did a similar thing recently with a vactrol. In fact, there's quite a lot of this that is similar, so you should take a look:

https://electricdruid.net/two-stomplfo-projects-mini-tremolo/ (https://electricdruid.net/two-stomplfo-projects-mini-tremolo/)

You could directly lift the buffer-with-gain I used at the input to fix your volume issue:

(https://electricdruid.net/wp-content/uploads/2022/08/InputStage-1.jpg)

I think you'd been thinking of putting the boost after, but it could go before instead. Or drop R2/R3/R4/C5 (the usual input components) and stick it after.
Duck's right though, you need to do *something* with that other op-amp. You can't leave it floating about like that. Not good practice.

HTH,
Tom

Brilliant thanks very much, once I can think straight I will re draw and post something using your ideas. At the moment things are a bit 'end of 2001', Dave.

QuoteI've added it below and labelled it 10K series... but then I saw you say it needs to be a voltage divider, so would that mean the resistor needs to move to the right (past the junction with the 2n5088?) and also should it be the same value as the 1M resistor that goes to ground after the audio input ( I am assuming that would be the second resistor in the voltage divider? I think a voltage divider need two equal value resistors?). In short, I'm not sure (sorry!)

The 10k *forms* a divider with the transistor.   No need to make a divider by adding a resistor to ground, the transistor is doing that already.  Without the 10k you don't have a good divider so the tremolo action won't be reliable.  (and yes 27k is fine.)

opamp pin 5 is being biased, for signal swing. biased is not powered, powered is for supplying current, biased is for shifting signal centre. always, an opamp needs supply pins connected to a supply, it should be explicit on any and every circuit diagram, but is sometimes shorthanded as being understood. which, on the circuit diagram of a super-simple circuit, is an error. because newbs.

the vico-vibe - pffffttt! TheOtherPlace? what do they know? breadboard it, see if it works. if it doesn't oscillate, try with a phase shift osc instead. or that opamp oscillator you've got in the leyland. british leyland? it'd go on strike, then rust.

Hi chaps

Thanks for the comments. I will try to reply tomorrow, my brain is very fogged at the moment, my knee looks like the football in Duck's avatar. I've redrawn the schematic with ElectricDruid's boost in it, I think it's correct... hope to be more compos mentis or generally amusing tomorow

(https://i.imgur.com/RI2bly6.png)

Quote from: moid on August 18, 2022, 02:31:10 PM
(https://i.imgur.com/RI2bly6.png)

Not bad, but you've gone and used that LFO divider as Vref again. Rob warned you against that earlier on. You'll have to use a couple more resistors and an electro cap to make a proper Vref just for the booster amp. Say 10Ks and 10uF.

Otherwise it looks good now.

QuoteNot bad, but you've gone and used that LFO divider as Vref again. Rob warned you against that earlier on. You'll have to use a couple more resistors and an electro cap to make a proper Vref just for the booster amp. Say 10Ks and 10uF.

Yes, using the oscillator "Vref" is a problem - in my eye's it's not even a Vref as the voltage there intentionally changes.   You need a separate Vref for the audio.

> make a proper Vref just for the booster amp.

And apply it to a cap-coupled "in" pin. (The "-in" pin can go to ground through a cap.)

(https://i.postimg.cc/Mfpqt8HZ/Moid-Trem-gain-42.gif) (https://postimg.cc/Mfpqt8HZ)

Quote from: Rob Strand on August 17, 2022, 06:12:27 PM

The 10k *forms* a divider with the transistor.   No need to make a divider by adding a resistor to ground, the transistor is doing that already.  Without the 10k you don't have a good divider so the tremolo action won't be reliable.  (and yes 27k is fine.)

Thanks Rob... I'm not sure what the 27K is though, I  don't think I put one on the schematic?

Quote from: duck_arse on August 18, 2022, 10:38:32 AM
opamp pin 5 is being biased, for signal swing. biased is not powered, powered is for supplying current, biased is for shifting signal centre. always, an opamp needs supply pins connected to a supply, it should be explicit on any and every circuit diagram, but is sometimes shorthanded as being understood. which, on the circuit diagram of a super-simple circuit, is an error. because newbs.

the vico-vibe - pffffttt! TheOtherPlace? what do they know? breadboard it, see if it works. if it doesn't oscillate, try with a phase shift osc instead. or that opamp oscillator you've got in the leyland. british leyland? it'd go on strike, then rust.

Thanks Duck - I just found the original post on reddit where the circuit creator was helping people make this tremolo and a few of them didn't realise that the opamp needed power - it's here in case any wants to read it, and there's a video in it showing the tremolo in action as well

https://www.reddit.com/r/diypedals/comments/kgs9ki/ultra_simple_tremolo_schematic_and_video/ (https://www.reddit.com/r/diypedals/comments/kgs9ki/ultra_simple_tremolo_schematic_and_video/)

What's a phase shift oscillator? Sounds interesting but I think I'd better get one pedal working before starting another (glances at plastic box full of unfinished vero constructions). Did British Leyland have a bad rep in Australia as well? I would've thought with the drier climate there that they would've been better off? They certainly rusted in the UK, or at least the vehicles they made in the 70s and 80s did; my dad used to drive one for one company he worked at and was never complimentary about them.

Quote from: ElectricDruid on August 18, 2022, 03:36:58 PM

Not bad, but you've gone and used that LFO divider as Vref again. Rob warned you against that earlier on. You'll have to use a couple more resistors and an electro cap to make a proper Vref just for the booster amp. Say 10Ks and 10uF.

Otherwise it looks good now.

Thanks Tom - it looks like I didn't understand that then! I thought (probably wrong!) that VREF was half the normal power going to a circuit, which is what I connected to... so I guess that's wrong... or maybe it's right, but I think Rob and PRR are explaining that I should have two voltage dividers because using the first one twice might cause issues?

Quote from: Rob Strand on August 18, 2022, 06:57:12 PM
Yes, using the oscillator "Vref" is a problem - in my eye's it's not even a Vref as the voltage there intentionally changes.   You need a separate Vref for the audio.

Thanks Rob, presumbly because a VREF needs to be a stable contstant value, and the one used here can fluctuate?

Quote from: PRR on August 18, 2022, 11:55:30 PM
> make a proper Vref just for the booster amp.

And apply it to a cap-coupled "in" pin. (The "-in" pin can go to ground through a cap.)

(https://i.postimg.cc/Mfpqt8HZ/Moid-Trem-gain-42.gif) (https://postimg.cc/Mfpqt8HZ)

Wow thanks very much PRR! Can I draw a vero layout from this schematic now? I asume the exclamation marks are to hightlight where I've gone wrong, or where I need to make changes? I have another question (from sheer ignorance) I put the audio into the negative input of the second opamp and you've changed that to the positive input - I thought (from looking at other circuits) that the audio went into the negative and the pot and other components went to the positive input - so presumably they can be swapped and it doesn't matter, or they need to be swapped in this instance?

Another question (sorry!) The original creator (in his reddit thread) mentioned that that circuit could be modified with a capacitor inbetween the 2N5088 emitter and ground to form a low pass filter effect which sounds rather fun and presumably I could add that on a SPDT switch with the output of the emitter going to the central pin of the switch and then one of the other pins going to ground and the other also going to ground by via a small capacitor like say a 80 - 100nF? Like the below - or would this cause something else in the circuit to go wrong?

(https://i.imgur.com/0y4vOPh.png)

He also mentioned that a high pass circuit could be made, although I doubt that would be possible without major changes to the first part of the circuit. I'm now wondering whether I could put a pot in place of the capacitor and have the emitter go to the wiper of the pot and then have two different cap values on lugs 1 and 3 of the pot, both going to ground to allow the low pass filter to have its cut off point adjusted? Sorry if I'm rambling, I am not 100% with the planet at the moment due to painkillers (don't do drugs and electronics kids!). My knee looks less inflated this morning so that's good!

one input will invert the signal out (- in) and the other will not invert the signal outputted (+ in). how each input is used and connected for gain/s is a little different. a topic for research.

aboot yer cap to emitter. yes, like that, most probably, I haven't tried it, but you will. and, for your differents cut-offs filter attempt - get a single pole double throw centre-off switch. [or double pole if that's all you have.] wire your smaller value cap from emitter to ground. connect switch common to emitter//small cap. centre position therefore equals small cap. connect one end/throw of switch to ground. connect other end/throw to a larger value cap, and the other end of that cap to ground. now when you switch one way, it shorts the cap and works stock standard. when you throw other way, larger cap is in parallel, and your filter shifts downwards. see?

> VREF needs to be a stable contstant value, and the one used here can fluctuate?

It DOES fluctuate! A lot. About 1/3rd of the supply voltage. That's how the oscillator oscillates.

(https://i.postimg.cc/RN6tvC2w/Moid-Trem-gain-Vref-42.gif) (https://postimg.cc/RN6tvC2w)

> I put the audio into the negative input

That's usually less-good. Here it leads to low input impedance and excess hiss. Non-inverting is really very common.

QuoteThanks Rob... I'm not sure what the 27K is though, I  don't think I put one on the schematic?

Early on in reply #5 you posted a circuit with 27k's.

Anything from 10k to 100k will work and trades off pickup loading vs noise.
Something like 22k might work a little more consistently than 10k with different pickups.

If you raise the series resistor you technically should increase the base resistor
on the transistor.   The way your circuit works has quite low base resistors and relies
on backing off the voltage.   Large resistors may sound a little different, perhaps
smoother.

Quote from: duck_arse on August 19, 2022, 10:57:37 AM

aboot yer cap to emitter. yes, like that, most probably, I haven't tried it, but you will. and, for your differents cut-offs filter attempt - get a single pole double throw centre-off switch. [or double pole if that's all you have.] wire your smaller value cap from emitter to ground. connect switch common to emitter//small cap. centre position therefore equals small cap. connect one end/throw of switch to ground. connect other end/throw to a larger value cap, and the other end of that cap to ground. now when you switch one way, it shorts the cap and works stock standard. when you throw other way, larger cap is in parallel, and your filter shifts downwards. see?

I thinks so... maybe? Let's see if I can translate your words into pictures! Using only the power of my mind! (whirring, ticking, mechanical noises, some puffs of steam and the hamsters start running in their wheel)

(https://i.imgur.com/wEjFbPR.png)

(my best second rate end of the pier magician act pose) "Is this the card you pulled from the deck?"

If I've drawn that correctly then that seems like a devilishly clever use of a switch! I've only got a DPDT On off On switch, so  I assume I just use only the lugs on one side of it and that will be fine? If it only works with a SDPT version then I will order one.

Hmmm that gives me ideas (probably not a good thing) about a high pass version... edit: nope, doesn't look like that is possible... oh well.

The reason for using a switch instead of a pot to control going between two capacitor values is because I would presumably also need a switch to activate / deactivate the pot, and also the resistance value of the pot might upset the voltage divider made by the 10K series resistor and the transistor?

Quote from: PRR on August 19, 2022, 07:53:54 PM
> VREF needs to be a stable contstant value, and the one used here can fluctuate?

It DOES fluctuate! A lot. About 1/3rd of the supply voltage. That's how the oscillator oscillates.

(https://i.postimg.cc/RN6tvC2w/Moid-Trem-gain-Vref-42.gif) (https://postimg.cc/RN6tvC2w)

> I put the audio into the negative input

That's usually less-good. Here it leads to low input impedance and excess hiss. Non-inverting is really very common.

Brilliant, thanks PRR, I will do as shown on your schematic. Your big wobble, small wobble notes made my brain revert to the eighties :) - Big Bubbles, No Troubles

Quote from: Rob Strand on August 19, 2022, 08:29:23 PM

QuoteThanks Rob... I'm not sure what the 27K is though, I  don't think I put one on the schematic?

Early on in reply #5 you posted a circuit with 27k's.

Anything from 10k to 100k will work and trades off pickup loading vs noise.
Something like 22k might work a little more consistently than 10k with different pickups.

If you raise the series resistor you technically should increase the base resistor
on the transistor.   The way your circuit works has quite low base resistors and relies
on backing off the voltage.   Large resistors may sound a little different, perhaps
smoother.

Found it now! blame that on painkillers (or stupidity, whichever seems more relevant!) Thanks for explaining.

I just had a thought - is there any reason why I couldn't put a high pass filter on a switch at the very end of the circuit? After the last 10uF cap (maybe use that cap as part of a high pass filter?)

The potential problem would be that the filter would affected by the impedance of whatever you plug into the output of the pedal, if I'm understanding you right.

Thanks Tom... oh so not a good thing then? Yes I suspect you are thinking the same thing. OK I will drop the idea then.

I've made a vero layout of PRR's schematic, so hopefully this will work (please yell if you see any mistakes!)

(https://i.imgur.com/Mu3u4CU.png)

the 10uF with + pointing to the depth wiper is backwards on the circuit dia. one end goes to the opamp output, which will be more positive than ground at all times, while the other end of that cap is referenced to ground thru the pot and 1k. the audio out 10uF is also backwards on the circuit dia, and should have a pulldown resistor fitted. 100k to ground will do. (move that bottom left 10uF cap way across right, save me some confusion tracking it across your layout. please.)

Quote from: duck_arse on August 21, 2022, 11:16:30 AM
the 10uF with + pointing to the depth wiper is backwards on the circuit dia. one end goes to the opamp output, which will be more positive than ground at all times, while the other end of that cap is referenced to ground thru the pot and 1k.

Thanks Duck - so you are saying the original schematic is incorrect, and I've copied that incorrectly as well, or just my layout is wrong? And do I need to change my schematic drawing as well? My brain is doing a confusion! Do you want me to just reverse that capacitor? That's what I've done in the below image.

(https://i.imgur.com/HaGq6Z5.png)

Quote from: duck_arse on August 21, 2022, 11:16:30 AM
the audio out 10uF is also backwards on the circuit dia, and should have a pulldown resistor fitted. 100k to ground will do.

Thanks - I've reversed it and added a 100K resistor on the far right of the circuit going to ground (had to add another column of vero to do that) Glad you mentioned this, I was about to start cutting up a sheet of vero, so I'll wait in case anything else needs to be added / changed.

Quote from: duck_arse on August 21, 2022, 11:16:30 AM
(move that bottom left 10uF cap way across right, save me some confusion tracking it across your layout. please.)

OK to do that I also had to move the cable connecting the wiper to the board to the far right, and shift a cut. Would you mind looking at my new image and seeing if it makes sense? Thanks very much for the use of your eyeballs!

I'll mess you up good, now. see your wrong, unmoved layout? under the TL0 there is a space 2 columns wide (12, 13). the moved 10uF could fit there, with a link as well. cuts to suit, you don't want me to do it all, do you?

as for that pulldown, hmmmm, above the TL0 is a mostly empty row. make a cut (9) under the 10k [left of pin 1]. shift the pin 4 cut under the TL0 across one (11 > 12) to the right, then use that pad for an under the IC link up to the line above pin 1. that then gives you an extra ground line, use that for your pulldown, no need for extra columns.

as for the cap errors, they appeared on the circuit dia, which you carefully followed on your layout.

Quote from: duck_arse on August 22, 2022, 10:55:50 AM
I'll mess you up good, now.

*blushing furiously while fanning face coquettishly* Oh my! I've got such a terrible weakness for bad boys! Who will preserve my dignity? Where is Mr Darcy?

Quote from: duck_arse on August 22, 2022, 10:55:50 AM
see your wrong, unmoved layout?

I sees it! And I raises yer another! *slaps layout down on the table heavily*

(https://i.imgur.com/kUcbcqw.png)

Quote from: duck_arse on August 22, 2022, 10:55:50 AM
under the TL0 there is a space 2 columns wide (12, 13). the moved 10uF could fit there, with a link as well. cuts to suit, you don't want me to do it all, do you?

as for that pulldown, hmmmm, above the TL0 is a mostly empty row. make a cut (9) under the 10k [left of pin 1]. shift the pin 4 cut under the TL0 across one (11 > 12) to the right, then use that pad for an under the IC link up to the line above pin 1. that then gives you an extra ground line, use that for your pulldown, no need for extra columns.

as for the cap errors, they appeared on the circuit dia, which you carefully followed on your layout.

That pulldown manouevre was reminiscent of Monty in the desert outflanking Rommel! Thanks Duck - I hope I've got everything right now. I did change the opacity of the 10uF to the left of the IC because it was so transparent that I couldn't tell which way round it was (so Imoved the cut that was under it to be beneath the 10nF that is to the right of it instead. Hopefully that 10uF is the right way around?

V0,4 - I don't like vero. I may have led you up the garden path with moving that cap right. I must have missed a connection. I think you now have it facing both ways, which will be wrong, obvs. ergh. argh. you've moved a wire, too. didn't spot that.

Sorry! I moved the jumper because I thougth I needed to after moving that cap? I can move it back to where it was if that helps?

arh, well, I hadda nutha look tonight. if you look at the layout V0.2, leave that link (at 5), move the cap at (4) across to (12 or 13), and stretch it [gak! cut my tongue!] across 4 strips. (but don't rotate it this time, unless that was one of the noted as backwards ones. no part numbers has me all a'flounder.)

Thankee kindly yer duckness :) I've drawn yer some new pickchurrs (wiv me own fair hands too!). I've incorporated all the changes you made about the 100K resistor at the audio output, and (i think) rotated the caps you wanted rotated as well. I've redrawn the schematic and labelled the 10uF caps as cap 1, cap2 etc and then put those same labels on the layout as well - hopefully that makes the debugging easier? I've rotated the cap that went to the depth wiper on the schematic as well. Do you think this one is OK now?

(https://i.imgur.com/PdPDxJq.png)

(https://i.imgur.com/waf9Ks6.png)

PS that streched cap? It's our secret, I won't tell no ones about it. Uh huh. Cross me 'eart!

I notice you've reduced the Boost pot from 47K to 10K. Have you tried it that way? That reduces the potential gain to only +6dB, not a huge amount (perhaps enough in certain situations, but that's for you to decide). The original 47K gives a bit more "oomph", but perhaps it's more than you need? 22K as a compromise?!?

Thanks Tom! Well spotted! I think I just did a CTRL C CTRL V from the Speed pot! I've fixed that now (by the way can I use a 50K pot here? I don't have any 47K pots at present). And you making me check things means I noticed I could lose a whole row of vero as well, so all the components in the bottom right hand corner of the layout can move up one (with the addition of a cut) and everything still looks good :)

(https://i.imgur.com/x3jUoM6.png)

missed the oaks? somehow, your circuit diagram now shows C5 reversed, and you've lost the 100k pulldown. but other than that, argh, my eyes.

There's trees in them woods you know! I've tried again, hopefully this one is less useless!

(https://i.imgur.com/eLMWsVi.png)

And thanks again, I will start hacking up vero board now!

QuoteAnd thanks again, I will start hacking up vero board now!

To me it looks a bit weird the way the "low pass" switch is done.   It's switching the cap on the ground side (the emitter) and that forces the LFO base current to pass into the audio path; via the 1M which is a terribly high resistance for the base current to flow through.   That has to cause some evil ticking.

If the emitter was grounded and the caps switched on the collector side I expect it would greatly reduce the ticking.  In fact for the non-low-pass case you might benefit by adding a largish cap so there's always a cap on the collector.

Well everybody, I know you've been on the edge of your seats after my last cliff hangar post of excitement, so in this week's episode of What Can Moid Break? I announce that.... (crowd takes a sharp intake of breathe) yep, I broke a tremolo! (sounds of general disapproval and a faint Ha Ha)

I was half way through building the vero when I saw Rob's post, but being the rugged, tough, devil-may-care individual that I am, thought, well I might as well keep going because maybe the universe will smile upon me..., although the result is not what Rob thought would happen, nor what I hoped would happen either! Never a dull moment here that's for sure! So the pedal passes sound in bypass (yay!) but when turned on it is silent unless the boost pot is set near the end of it's travel clockwise, at which point there is suddenly a lot of volume and hiss, but no tremolo. If the boost is set to the maximum extent the volume cuts out again. So there is a small area of travel of the pot at which audio goes through the circuit and gets louder... near the edges of that audio 'arc' the sound is very spitty and gated, in the middle it sounds like boosted clean guitar. All of this happens with the SPDT switch set to central position which I have just realised is one of the low pass settings.... aha it looks like the two low pass settings allow the audio to come through, I'm not sure if they are actually filtering higher frequencies out though.... and setting the switch to be 'normal' tremolo doesn't let any audio through.

Twiddling the Speed and Depth knobs does nothing except imbue the user with a sense of melencholy and a wistful faraway look in their eyes.

The Boost pot is a 50K lin (I didn't have any 47K pots) but I doubt that would make much of a difference? I checked it's resistance on my DMM and it happily travels from almost 0 to 48.9K.

The voltage on the chip (TL072) is (9V power to circuit, nothing plugged into the audio sockets):

pin1: 4.6V DC
pin2: 4.52V DC
pin3: 4V DC
pin4: 0.002mV DC
pin5: 5.6V DC
pin6: really odd - starts at 2.1V DC but keeps falling slowly - after 1 minute it had fallen to 1.7V and was still going but I got bored of watching it and stopped measuring - this seems pretty weird?
pin7: 7.97V DC
pin8: 9V DC

Does any of that sound interesting / make you laugh? Thanks for your thoughts :)

Ok so I plugged the circuit into my iphone so I could play music through it while testing it with an audio probe. Using the phone, audio goes through the circuit with no tremolo at all. Different settings of the spdt switch do nothing. The boost pot goes from unity up to ferociously loud fuzz and works across the whole of the range of the pot. It seems to me that the boost side of things is fine but the tremolo part of the circuit doesn't do anything. Could anyone give me some advice on what to check next? Thanks

might we see photos of the device in question? solder side and components, please. also, what voltage readings are you having on that transistor?

Now why didn't I think of that (no, don't tell me, I know I'm special - my teacher said so!)

the circuit in all its glory
(https://i.imgur.com/UbVeI0K.jpg)

Close up (with heavy depth of field for you cinematography fans!)
(https://i.imgur.com/4OYt4iR.jpg)

Underside
(https://i.imgur.com/FmFmPEN.jpg)

transistor 2n5089 - the circuit was plugged into a 9V DC plug from mains (no battery) and nothing was plugged into the audio jacks.
Collector 1.256V DC
Base 1.743V DC
Emitter 1.255V DC

Thanks yer duckness!

gaze, moidy, if you would, upon your last posted circuit diagram. see! the emitter of that circuit connects to ground, or a capacitor, so will show 0V at all times. no, really, stay with me ..... also see the base connected to - no DC volts, cause of old mate "cap1" and the resistors to ground. and as for the collector, the 10nF connected to blocks DC from the opamp end, and that only leaves the input resistor/s, one of which pulls to old mate ground, and the other which connects to signal, which we all know carries no DC offset.

so. something isn't wired as your circuit shows, and is loading that transistor with all sorts of DC, turning it on and eating yer signal. switch power OFF, pull the transistor from the socket, meter with yer meter set to ohms from each socket pin to places like V+, ground, signal in resistors, the opamp pin 3, etc. then work  out where the badness is. enjoy.



I think your layout has errors. the transistor appears to be one row low, the collector is connected hard-to the input, and not to the 10nF to the oppie. PERHAPS - cut that link at top of 5, and link it to D instead. I stopped looking then, there might be more.

the perils of veroboard - nobody wants to look at it, so errors go un-scruted.

we might be able to save it. lift out the 10k at 9C-9F. make a cut at 14C. add the 10k across that cut, 11C-15C. add a fly link from 16C back to 9F [pin 2]. that should correct your boost woes. you could/should also add a stop resistor for the boost pot, it could go on B [with cut!], alongside the 10k you just moved.

your speed pot lower wire showing on your layout - I think that pink wire should go to the bottom row where the 2 10uF caps join the 220k. you'll be amused to hear that the speed pot should also have a stopper R.

and if that don't get it running, whell, I dunno.

Wow, thank you so much Duck! I've been stuck back at work this week alas, I will try to look at this tomorrow after some sleep and draw a new picture for you to cast your gaze over.

Sorry about the slow reply, I had to cover for a colleague today at a graduation ceremony and spent the weekend learning how to pronounce a variety of complex student names so I could call them out in front of them and their parents... 800 of them... that was a very nerve wracking morning! I think I only made two slight mis-pronunciations (Lithuanian and Polish are not easy ones for surnames!)

Anyway I think I have understood all you said and made a pretty picture of it:

(https://i.imgur.com/BabuHrC.png)

The new cuts are in bright yellow so I remember to make them myself later (and so you can see if I put them in the right place). I used 10K for stop resistors; is that correct? I think you said to use that on another circuit, but maybe that isn't the right value for this circuit? I've written stop 10K on them. The one on the speed pot, well unless I had it hanging off the board (which I knew would provoke rumblings of discontent from the good members of this board), the only thing I could think of was to stand it on end (yes I know you don't like that either, sorry; I reckoned that was less of a sin than hanging the resistor off the board... think of it as cordwood with a kink :)) - and then attach the pink cable to the next row up (as you can see in the picture). Is that a good / bad idea? I could stick the resistor off the board or straight on the wiper of the pot and connect that to the board if you prefer?

If the above looks good, let me know and I'll start de-soldering and re-soldering.

Thanks for your noble efforts at trying to bend veroboard around your head. It might cheer you up to know that I've bought a small sheet of perfboard, if I get some time around Christmas I might try to build something simple on it and see if I can actually make that work (I've always failed at perfboard in the past), but if I screwed that up at least it might be less of a misery for people like your goodself to debug what I did wrong?

(https://i.postimg.cc/PJ7qM3DS/moidy-correction0-8.png)

see if this makes sense. I think it correct, based on V0.6.

[later :] reading antonis has just reminded me - stop resistors. you need to pick the value to suit the app, really. in the boost section, with the pot at 0, the stop will set the gain w/ the 10k to CAP4. so unity w/ a 10k stopper, but you could have a little reduction available, just in case. maybe 5k6 or so?

as for the oscillator - sets the highest freq available with that cap value. I dunno how fast it runs, but the 10% rule can be applied, use 1k. if the osc conks out at high speed, you need a bigger stop R.

Thanks very much Duck and Antonis. I redrew things:

(https://i.imgur.com/CTcD162.png)

Is that right? I was a little unsure which resistor was the 5K6 one (of what was two 10K ones lying horizontal above each other at the top of the board) so have I put that the wrong way round?

I think everything else is right now

Who's Al? And why is he so hungry?

Quote from: moid on September 13, 2022, 03:56:29 PM
Thanks very much Duck and Antonis.

You're welcome but I didn't have the slightest contribution in the present thread.. :icon_eek:

I was hoping antonis would point out that the boost stage is a non-inverting config, and as such never gets below unity gain. it's in the numbers. so - you can probably get away without a stop in the gain pot - or just make it 1k, keep it to cover that ugly cut you made. and yes, you picked the wrong one to make 5k6, it should be the other one.

I hope it's right - I don't want to look any more. ultra simple my screen name.

Quote from: antonis on September 13, 2022, 04:54:03 PM

You're welcome but I didn't have the slightest contribution in the present thread.. :icon_eek:

In that case you should see yourself as a 'spiritual advisor' to the thread :)

Thanks to Duck again - a new picture; this should be fine and I will try to rebuild this board this weekend - all your final suggestions should be here
(https://i.imgur.com/L6xRtoY.png)

Good job!
I'm very interesting in a small tremolo circuit. This is not so small, anymore, but I understand that some parts are useful or necessary.
Let us to know your progress. :)

no sir! your 5k6 should be the "1k value doesn't really matter", and your 1k should be the 10k in the gain leg with the 10uF cap.


go the swans.

Thanks Duck - hopefully this is all happy now :)

(https://i.imgur.com/wXncVQL.png)

Some success! After changing all your suggestions Duck we have a tremolo! On the normal setting (not low pass filter) this is a very hard edged square wave tremolo. It's rather fast - the slowest speed is 3hz, rising to a near ring modulation at 25Hz (which is quite interesting, I've never owned a tremolo that could go that fast!). It would be nice if it could go slower, but that's probably not possible without changing something vital I guess? I presume making this do a triangle or sine wave would require a completely different circuit?

The boost works too, at minimum setting I get unity, and maximum is louder (my guess is 6 -10dB more?). It's fine.

Where things aren't working as planned - as soon as I switch to either of the low pass filter modes the speed rate makes a constant low pitch thumping sound... and there doesn't seem to be any filtering at all, maybe very slightly less bright than the normal setting, but nothing more than that - it's subtle if it is doing anything, but it might just be hidden by the thumping sound. The boost makes the thumping much worse if I turn that up. Any guesses what to do next? If the pedal can't cope with a low pass it's not the end of the world; I haven't drilled the enclosure yet, I can just hide the switch inside! Thanks!

the one you call "cap 2" izz the timing cap. add to it in parallel, another 10uF for a start, will get you slower. also, a larger value for the speed pot = 47k or 50k or 100k, will slow proceedings and give more range.

the 10nF cap from pin 5 tp pin 7 on the oscillator is there to slow the edges of the oscillator some. you might try adding larger value there, again in parallel, but not 10uF this time. and it might lessen the squarity of the chop. at some value of added cap, the oscillator will stop.

as for your thump-a-matic switch - see Rob's comments earlier in thread.

Quote from: duck_arse on September 19, 2022, 11:08:53 AM
the one you call "cap 2" izz the timing cap. add to it in parallel, another 10uF for a start, will get you slower. also, a larger value for the speed pot = 47k or 50k or 100k, will slow proceedings and give more range.

Aha thanks Duck - I could (maybe) squeeze another cap into the board, by doing some hacky things with an SPST to bring the extra capacitor in parallel with the 10uF. If I change the Speed pot to a higher value I won't be able to get the really fast audio rate tremolo anymore though will I? I think a cap on a switch might be more what I want - I want to be able to go that fast because no tremolo I own can do that, but it's also nice if the tremolo is capable of slower speeds if I want them.

Quote from: duck_arse on September 19, 2022, 11:08:53 AM
the 10nF cap from pin 5 tp pin 7 on the oscillator is there to slow the edges of the oscillator some. you might try adding larger value there, again in parallel, but not 10uF this time. and it might lessen the squarity of the chop. at some value of added cap, the oscillator will stop.

OK, this is somewhere where a SPST switch and some abuse of where a cap goes might be possible - I could try experimenting with different values and seeing what happens - I presume as the capacitor value goes up, the steep sides of the tremolo effect become more sloping, but at a certain point the slopes become too shallow and begin to remove almost all the audio?

Quote from: duck_arse on September 19, 2022, 11:08:53 AM
as for your thump-a-matic switch - see Rob's comments earlier in thread.

I will try to understand Rob's comments again - I think I will need to draw something to ask if I understand them though, because I can think of two ways of interpreting what he's written, and I'm not sure which is right! I will make a schematic diagram and post it soon.

One other thought - if I was to remove the switch for the two different low pass filter options (so on my vero board G1 and J1 were just connected with a short cable) I would just have the 'normal' tremolo effect. Would it be a bad idea to make a tiny daughter board with an RC Filter on it and place it between the Audio Out of the board and the 3PDT switch? Would that remove the issue that Rob was talking about with DC going into the audio path? If it does, I got very excited to think that I could make a small vero circuit with a low pass filter and a high pass filter on it and hopefully use your ON off ON SPDT trick to cycle between normal tremolo and high pass or low pass versions. Good idea or baaaaad idea? As Lou Reed once put it, "the possiblities are endless, and for me to miss one, would seem to be groundless"... which could well be the root of my problems :)

QuoteIf the emitter was grounded and the caps switched on the collector side I expect it would greatly reduce the ticking.  In fact for the non-low-pass case you might benefit by adding a largish cap so there's always a cap on the collector.

try this, easy peasy. [some typing follows] pull the link at 5E-5D. pull the 80nF cap at 5G-5J and fit it across 5E-5F [up, back, links and cuts, whatever]. this puts a "big" cap in the collector line.

then you need to shift your cap switch, and the 100nF, so they switch across that 80nF at the collector instead - no connections to ground on the switched parts now. I tried to suss the movements, but it did for me, no parts refs combined with vero. circuit redraw needed.


as for speed - yes sir, no sir! the fast speed corresponds to the low resistance setting allowing your timing cap to charge and discharge at a greater rate. you can make your speed pot megohms and it won't affect the fast rate, cause the low end is limited only by your famous stop resistor. so a slower rate cap on a switch is the way to go. [too big a speed pot will make fast setting very very hairy, all squashed into a little rotation.]

as for shape, you're stuck with it. it might improve with the caps shifted to the collector, but that's doubtful. as for the 10nF slow-down cap across the opamp, that's not for putting on a switch. try adding 10nF or 22nF or so, see if it makes any change to the sweep. again, probably knott, but werth a tri. somebody mentioned the phase shift oscillator early on [might have been the twin-tee instead], that's the best method of getting simple sine into a trem. but probably the transistor shunt method of trem will limit the goodness of shape, no matter what drives it.

Edited this a bit, not sure if that makes it easier or worse for comprehension... sorry if it's gibberish, will try to get some sleep tonight and hope to be more compos mentis tomorrow!

Hi Duck Sorry about the slow reply, all my students turn up next week and things are getting very hectic... students, thousands of 'em!

Thanks for your ideas and guidance! I've tried to redraw them, I'm very confused about a couple of parts though.

(https://i.imgur.com/OwlQrsl.png)

The changes to the cap switch - it looks to me that I only need an SPST for this switch now? edit: I bet that's an SPDT isn't it? So there are only two modes - normal and low pass tremolo (I can live with that, I couldn't figure out where a third cap would go now or how it would attach to the board!). Will I need to make a cut somehow between the transistor Base and the 80nF cap - between 5F and 4F? And shouldn't that 80nF be attached to D5, not E5? So that it connects to the 10K from audio in?

I moved the 100nF so it is positioned diagonally (sorry!) and put a cut at 5C so it doesn't cause any problems elsewhere. I moved the cap switch cables to 1C and 1E, so that if the switch is now SPST, in one switch direction the capacitor is not added to the audio line, and in the other it runs in series with the 80nF... now that looks odd to me...I can't figure out if that works or not. Hmmm that switch should be SPDT shouldn't it?

Regarding the addition of a speed switch, does the SPST on the right side of the layout look right? I'll solder cables to the legs of the cap that is on the board and then add in an additional 10uF via the switch. Damn I just realised that SPST should be labelled SPDT... I do wish I'd had more sleep last night.

Thanks for your patience, I'm sorry to be such a drag... badly running out of time now and will soon have to give up building stuff until Christmas :(

(https://i.postimg.cc/44hS0Qp6/moid-tremmer.png)

like this. still centre off, spdt. as for the osc slower, you only need single pole single throw - but use a single pole double throw anyway, cause you've got those. my eyes are grinding, so I'll leave the circuit to vero translation to ..... well, anyone.

cap stays away from the base, don't be cutting there. no sleep till xmas.

Ominous rumbles from the sky... lightning flashes across a dark, hilly landscape revealing a ruinous gothic castle... flickering electrical sparks illuminate a dungeon laboratory... a mad cackle rings out from within the room:

"It's alive! The topic is alive! I have brought the dead back to life..."

Melodrama over, I've finally had the chance to look at this circuit today (it has been sitting on my desk since last year and I haven't had any time to do anything with it sadly - it's a tragic memento of time lost :( ). I have now re-read the thread to try to remember what everyone's advice was for the circuit and found Duck's final schematic (thank you very much for drawing this, I'm really sorry I didn't reply at the time; I didn't even see it until today... what a horrible year it has been). I have redrawn my vero layout, if it's not so late that it's ridiculous, please could you check it to see if it looks good and if so I can get on with soldering this and finish it! There is a double link between the 10K resistor and the collector because I need to connect the collector and also send the signal to the boost part of the circuit. I also noticed that my 80nF cap was actually an 82nF, and I've moved the switch about to connect the new capacitor layout for the different tremolo types. I think that is all the changes. Thanks very much!

(https://i.imgur.com/jmSwrAX.png)

moidy - back with us? how's?

moidy moidy moidy - observe your 5088. it has nothing attaching to the emitter. should be ground, according to the snippet I see above. and pin 4 of the IC is ground, so if you shift the transistor down by one, and shorten the 10k to base by one, you will have that bit right. also, observe that double link hole 10k and link. it shorts your pink and blue wires to things, so it is wrong. I think the bottom of the 82nF comes down one [so now spans three] and the blue off-board wire comes down one. the 10k at A3/D3 stays where it is as it connects to that 100nF at D7. so delete that link at D/E3.

yerrrssssss, I think that's right. copacetic, even. draw it up again, give us a geek at it, we'll see what is. where is the circuit diagram, pages back? I'm too scared to look.

Thank you Duck! I'm back (at least until early September). I'm kind of like one of those migratory birds that shows up once a year and you get all excited about the little bugger because you haven't seen one in ages... and then it shits on your car! My students are all on holiday, so I am too (yay!). I hope next year won't be as crazy because I've changed jobs and am no longer in management (phew!) so hopefully that means I might get to create things even during term time... although knowing my luck something is bound to go horribly wrong, the future is rather uncertain where I work at the moment. Anyways lovely to hear / read your reply! Glad to see you're still here :) I'll try not to crap on your car! How is your good self? Hopefully surviving the Winter?

OK I did some scribbling and we have the below beauty:

(https://i.imgur.com/PZ0kEwy.png)

urghhh circuit diagram... yessum, about that... (looks sideways nervously, tugs at collar), why I'm sure I kept that up to date with all those changes we've been making, yessir it would be a terrible thing if I hadn't done that, I mean that would be really amateur wouldn't it? I think I saved it in a very special secret hidden place on a back up computer in another location and it might take me a little while to find it again, so you just wait there and I'll be back faster than you can say "If practice makes perfect and perfect needs practice, I'm perfectly practiced and practically perfect"... exit, stage left

I don't own a car, and current winter is like your summer. with less rain.

well I think that looks about right - if all the other part was right, the new part at least appears to match the fragment of switch circuit I posted earlier. so why haven't you finished it yet?

It's a good thing you don't own a car then, I'd watch out for any outdoor flat surface you do own, because guess what? The circuit did not like being fiddled with at all, and we now have a 6dB boost, but no tremolo... oh and I discovered I wired the Boost backwards, so that needs fixing too! There's no success like failure...

Flipping the switch betwen the three tremolo modes does cause a slight tonal change to the sound (I think) and on one option there is a loud pop when I switch to it... no sure if that matters. The speed switch does nothing I can perceive. I tried swapping out the 1K resistor that I had socketd that I think Rob suggested; and I tried 10K and 100K and no joy... should I try something higher? I was assuming it would be a small value above 1K to make it work if that was the issue.

I'll try to draw a schematic for this later tonight, but thought I'd post my findings so far in case they mean anything to anyone.

Aha, was looking at the back of the board under some brighter light and I think I can see some mistakes (and one lead has popped off the board!). Will try knifing things and re soldering later, hopefully with better news.

Well folks I bet you were on the edge of your seats after this evening's cliff hangar? Will the hero get the girl? Will the villain take over the world? Will the tremolo activate? Stay tuned to this week's thrilling adventure!

Spoiler: Kind of :)

OK once you remove the lump of solder that was bridging a couple of rows of copper trace (whoops) and you discover that your amazing soldering skills had caused part of another row of coppper to detach from the vero (ooops) and you re attach that cable elsewhere, and you re wire the boost pot the right way round, well we have some success. The normal tremolo works, although it seems less choppy now (not that that is a bad thing, I quite like it). The depth is also not there as much as it was - I don't think it fully cuts the signal out, but I might wait until my son is around tomorrow to ask him to use his fully functioning ears to see what he hears. I've also appeared to have soldered the depth pot the wrong way around...d'oh... maybe changing that would fix the depth amount?

Onto the tone switch fun. The middle (off) selection works fine - standard tremolo as mentioned above. Switch down (yellow and blue cables) gives either a very interesting choppy / glitchy / ticking tremolo (if the rate switch is set to slow and the boost is on maximum) or if the rate switch is set to normal (taking the extra 10uF cap out of the circuit), no audio will go through the pedal at all. How's that for weird? Hmmm re testing this I find constant ticking is present, but if the rate switch is set to normal and the boost is turned down I do get glitchy trem, but one where the amount of guitar signal in the audio gets less and less as the boost is turned up (unfortunately it is replaced with loud ticking). When the boost hits maximum all audio (and ticking) is removed and the circuit does nothing except make loud static hiss (great white noise generator!)

Tone switch up - (purple and blue cables active) yes definitely works, sounds great, lovely pulsing soft sound - works when the speed switch is at either setting.

The speed switch. The extra 10uF cap halves the speed of the tremolo at the slow end, but seems to be able to still reach near ring mod territory at the fast end of the rate pot. Would increasing the 10uF to something bigger (47uF?) make the tremolo slower? I've got some 22uF and 33uF if those are more appropriate?

Oh yes the boost is very fuzzy; but in a good way - I like the pedal with it turned up to the maximum although the fuzz is strongest on the lowest strings - the high E string comes through as louder but not fuzzy. With the boost set to minimum the effect lacks much character and the tremolo seems weaker. I don't recall it being as fuzzy as this before! But I like it so let's not panic about it!

At the moment I am tempted to say I'll keep it. If the speed switch could go slower that would be good. If the depth was stronger that might be useful (a larger pot value maybe?) but it's no major issue. If the ticking on that one mode of hte tone switch could be fixed that would be coool - I like the odd stutter it has!

Quotethis evening's cliff hangar

where do you park the planes, then?

circuit diagram first, more of your fooling and fixing, then we worry about what is right and what is working and how to mod faster or slower. and photos, as per the rules. please.

Quote from: duck_arse on August 08, 2023, 10:30:45 AM

where do you park the planes, then?

In a vertically orientated stack of hangars, going up the cliff of course - they are only for helicopters and Harrier jump jets (what other planes are suitable for such an exciting post?)

Anyway luckily I managed to bump into my wife's brother's cousin's girlfriend's dog (you wouldn't know her; she goes to another school) and ask for the schematic file from their laptop and so here it is! Good thing I kept that fully up to date :)

I got my son to play through the circuit today and we discovered the fuzz sound from the boost is not fuzz, but me not realising the high volume I had the pre amp on my DI box set to... whoops! Turning that down to something sensible makes the boost clean. However fuzz fans, all is not lost, because while playing with the circuit (contemplating adding a larger capacitor to the speed switch to slow the LFO down more) I accidentally touched a 10uF cap from ground (actually to where the 10uF stripe side leg - marked cap2 on the schematic) to pin 3 of the boost and the circuit turned into a super loud fuzz! My son immediately said keep that! So he wants that added as a switch (SPST should do). It did sound pretty good, I have to say - it keeps the tremolo, just adds a massive fuzz on top. We also tried a 1uF instead of the 10uF but that just made things slightly louder but clean. Adding a 47uF seemed to cut the entire signal, and a 22uF removed all the high frequencies and added very distorted bass only and sounded awful, so 10uF seems the magical one to keep. Turning the boost pot down does tame the fuzz if required.

Anyways you wanted some pictures:

Schematic
(https://i.imgur.com/TL1508r.png)

Photos (please don't scream when you see the soldering - this was quite neat until I had to start desoldering things and putting them back together - that's why there are some unused sockets on one side - and there are other components floating about a bit...

whole circuit
(https://i.imgur.com/Kd2PVHd.jpg)

Close up of top of board
(https://i.imgur.com/xgI7tl1.jpg)

Close up of underside of board
(https://i.imgur.com/hQRRLjB.jpg)

Thanks again!

a few prelim q's from your circuit diagram before I off to scrute the whole - that 1k between the speed pot and the 10uF cap - what's that for and where did it come from? it will really limit the slow speeds for sure. your added 10uF big boost switch cap - it is bypassing the 10k R in the inverting in leg of the opamp, so it is kind of legit. would probably be as easy, and better, to just switch a low value resistor in parallel with the 10k, tho, I think and get shot of that extra cap. the moid-reutz gain-leg mod.

Well we are really into Alice in Wonderland territory! Curiouser and curiouser...

I was adjusting things today and swapped the 10uF capacitor on the rate switch for a 22uF and that worked - I got a much slower tremolo which is also slower at the fast end of the rate pot so that was good (I did also try a 47uF but that was too slow; the notes decayed before the LFO completed a cycle - probably OK on synths pads with reverb, but no good for guitar). So that was the good part. While testing the fuzz switch I noticed the massive volume boost when using it (not an issue, it sounds great, but wow is it loud - although tameable by reducing the Boost pot). So I switched off the fuzz, and started testing the normal boost part of the circuit and it seems that the circuit only gets to unity when Boost is on maximum - anything else is quieter... I don't think I ever switched between bypass and the circuit up to this point (d'oh) so didn't realise that the Boost isn't working as I thought... have I wired the pot backwards? Or done something else stupid?

I also noticed I wired the depth pot backwards, so go me!

Quote from: duck_arse on August 10, 2023, 11:16:24 AM
a few prelim q's from your circuit diagram before I off to scrute the whole - that 1k between the speed pot and the 10uF cap - what's that for and where did it come from? it will really limit the slow speeds for sure.

Hi Duck, you must've posted just before I did! The 1K was a suggestion of someone in the thread... oh it looks like I suggested it, how did I come up with that? You then advised on some different values to try in post45 https://www.diystompboxes.com/smfforum/index.php?topic=129499.msg1253431#msg1253431 (https://www.diystompboxes.com/smfforum/index.php?topic=129499.msg1253431#msg1253431)

I'm not sure why I settled on 1K though - should I try 10K (one of your suggestions?) Oh in post 48 I think you said to try removing it? Maybe I should do that?

Quote from: duck_arse on August 10, 2023, 11:16:24 AM
your added 10uF big boost switch cap - it is bypassing the 10k R in the inverting in leg of the opamp, so it is kind of legit. would probably be as easy, and better, to just switch a low value resistor in parallel with the 10k, tho, I think and get shot of that extra cap. the moid-reutz gain-leg mod.

Wouldn't using a resistor change the sound compared to using the capacitor? Or is the capacitor merely acting as a jumper in this case and so as little resistance as possible is required? I could take a cable out from C9 on the board to an SPST, to a resistor and then back to C17 on the board - is that what you mean?

The second harmonic tremolo now seems to do nothing but add ticking... urghhh I think feature creep may be killing this circuit. Maybe I should just swap that switch for an SPST and have normal tremolo and the one harmonic that does work (I think that's the 100nF). It's got hot today here and I think the sun nuked my brain this morning (was out all morning looking for a colony of rare wildflowers for a conservation group, sadly it looks like climate change has nuked them all).

Today's update: In the interests of science, I tried removing the 1K stop resistor - and if I do that, the circuit stops all tremolo (guitar still passes through, but not tremolo). So I put that back! The ticking horribleness seems to be coming from the 100nF capacitor, which goes into a socket that I made from bits of a broken socket from another circuit (I like to recycle!) but when I tried to put a new capacitor in place on the 100nF (just hoping it was a dud capacitor), one of the legs would not fit into the socket so I will try removing my recycled socket and place a new on in the same spot and see if that helps. Also the boost seems to work today! Although I'm now getting a high pitched oscillation when the fuzz is on and also the switch that selcts the 100nF now cuts all audio when that option is one... I wonder if this circuit needs to be in a box so it is shielded? It is certainly tempermental! At least I'm in a better mood today, I managed to build an modified Autowah last night and it worked first time (that's pretty rare for me!)... now I might need to add just one more wafer thin mod to it to make perfect... hope you're all having a good Friday!

good friday was at easter.

now see, the thing I did rong last night was to delete my local of your layout, so I had no guide while lookink at yore bilt. scuse my typing. and I looked at the underside of your board .................



that 1k stop resistor - you have misplaced it on your circuit diagram, so we point and say - what's that? it should be drawn in series with the speed pot, whereas you have it parallel. so it was boarded right, and should be left well alone.

about your bonus 10uF boostering cap. the gaining is set by the 10k in series with the 10uF, from (-)input to ground. and the formula tells you at what low frequency the boost will start from, and how much gain is determined by the 10k and the feedback pot setting [and, obvs, its series stop resistor]. when you add that 10uF, it is parallel to both the 10k and the 10uF, so you are basically saying FULL BOOST at all freqs, negating the effect of the resistor. changing the resistor value will have the same/similar/not much difference to the sound, and will behave in a much nicer fashion - no whumps or chargings.

so just switch-add in parallel a resistor, ?220R? 100R? 330R? I dunno R? but across the 10k only, and be done. or complain, we take both types.

don't be boxing a non-working build, you are asking for trouble when you do. and that cap tone switching business - we need to see the toggle switches wiring a little clearer before we can say. I say we. oui.

Quote from: duck_arse on August 11, 2023, 11:12:54 AM
good friday was at easter.

How time flies when you're having fun!

Quote from: duck_arse on August 11, 2023, 11:12:54 AM
now see, the thing I did rong last night was to delete my local of your layout, so I had no guide while lookink at yore bilt. scuse my typing. and I looked at the underside of your board .................



that 1k stop resistor - you have misplaced it on your circuit diagram, so we point and say - what's that? it should be drawn in series with the speed pot, whereas you have it parallel. so it was boarded right, and should be left well alone.

This one is confusing to me - the 1K is in exactly the same place on the vero as it is on the layout? Maybe what looks odd is that DIYLC has this annoying habit of drawing an extra row of holes at the bottom of the vero board. I've done a new layout (showing other changes) - hopefully this looks okay now?

(https://i.imgur.com/zD8Ij4X.png)

So other changes - the switch on the left of the layout has had its cables untangled, and now I get normal tremolo in the middle setting and harmonic tremolo when the 82nF is engaged, but now just silence when I switch to the 100nF (better than the awful shrieking noise that used to be present I guess). I could try removing the socket that holds the 100nF and soldering a new one in and trying that if you think that's a good idea?

The fuzz switch has been added as you described. 100R turned out to be the best value - lower than 100R and the tremolo vanished and I just got fuzz; higher than 100R and there was terrible pounding thumping noise that never went away (the pulse of the tremolo)... actually I still have that with the 100R, but at a lower volume; it's a bit annoying. Neither is quite as chaotically strong as the original 10uF cap trick, although I tried socketing that cap in to the sockets that hold the switch cable and 100R (instead of the 100R) just to see if that would do anything and it worked, but with a high pitched pulse noise that was timed to the tremolo speed... yikes. So 100R and heartbeat it is I guess... I can lower the volume of the heartbeat by reducing the boost level and also the depth level on the pots (but the tremolo is reduced as well). I'm tempted to leave that where it is at the moment! It's only really noticeable when the fuzz is on, the rest of the time it is very quiet. I'm not sure if that thumping heartbeat was present when I ran the 10uF cap straight from Lug 3 of the boost to ground... I don't remember it being there. Also when I used the cap, the fuzz 'filled in' the tremolo sound, so that the tremolo only appeared as the note decayed which was pretty awesome, and that has vanished by using the resistor... how bad an idea would it be for to go back to that plan? - I know you mentioned there might be whumping noises, but I think I've got those now anyway!

And the boost is also back to not being a boost anymore (if it ever was). If the Fuzz is off, the boost needs to be on maximum to keep the signal at unity (maybe slightly higher than unity?). I started AB ing the bypass and tremolo, and the bypass sound is louder, so the Boost pot starts by removing all volume and slowly adds the volume as you turn it. Quite what I've done to this circuit is anyone's guess. Feel free to say "Enough! Let's drop this damn thing"; it's driving me nuts as well, and I hate passing on my misery to those who don't deserve it. Thank you for your time and sanity!

Some more fiddling today, and some embarrasing mistakes  :-[. I started changing the fuzz part of the circuit to run a 10uF from the boost pot lug 1 to ground (not lug 3 as i said before, I can't count!) because it gives better tone to the fuzz (kind of like a %^&*ed wah) and I realised a couple of issues. The fuzz tone is actually mostly just the boost absolutely hammering the pre amp of my DI box... I wasn't paying attention to how loud I must've had the input volume on the DI box set to!! If I turn it down so that the incoming volume is not clipping then the boost is just loud and clear until I get near the maximum end of the pot sweep at which point it is clipping nicely (with tonal modification courtesy of the 10uF cap). So the fuzz is kind of a lie :( The boost pot is making things louder, but in a clean(ish) way! If I switch between bypass and boost pot turned down to nothing the volume is almost the same (bypass is slightly quieter). Things get considerably louder when the 10uF cap is switched in, with additional tonal shaping. Ho hum... I guess I will just have to push this into a fuzz pedal in future (or just overload my DI box!)

The 1K resistor does not sound as good. No idea why, but it sounds loud and distorted but without the tonal shape of the 10uF, and with more thumping heartbeat noises... So I think I will move the switch back to my original design. Sorry I'm going back against your good advice Duck but it honestly sounds better.

If anyone has any idea why one of the harmonic tremolo switch settings kills all audio then that would be cool! With that solved I could start boxing this mass of wires!

ohhh, I love embarrasing mistakes .....

which 1k resistor doesn't sound as good?

the stop resistor I confused you with was drawn wrong on your last posted circuit diagram/schematic. it was correctly placed on the board, build and layout. the tone switch, well, if it works in two positions, I can't see a reason for it not to work in the other, except build error.

I was thinking to switch the gain-leg resistor instead of the cap as the cap would almost certainly whump each time you switched it in. the osc whump is a bonus? I suppose the 10uF across the full leg is still valid, if it does what you want. but further fiddle has muddied your results - which bits still work and which don't?

I think the loading on the Cv side is too low in the OP schematic ...

case in point, notice the op-amp isn't driving that side-chain node directly - but rather thru the SPEED control resistance

for one, an overly low output loading produces a squarish Cv voltage to the base of the bipolar transistor
it also prevents sufficient signal swing from forming there as well

... at least according to TINA, which i don't think is wrong here

notice also, as Rob pointed out, my inclusion of an input 10k resistor to form a voltage divider,
similar to how the Arbiter Trem-Face does it ...

https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/ (https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/)

this change allows for the potential of a more rounded TREM response
as opposed to that of a hard clamp ...

---

now, if instead we reduced this loading by increasing the side-chain resistance to around 50k (versus 5k or so as posted) two things happen:

the Cv swing increases to the point where we get (full trem) "choppy" action,
and the Cv waveform is now more triangular, what we would expect it to be in an a passive square-to-RC-expo-triangle conversion

http://www.lynx.net/~jc/LAYLAND-TREM-50k-MOD-linear-range.png (http://www.lynx.net/~jc/LAYLAND-TREM-50k-MOD-linear-range.png)

---

the question, can this passive bipolar-clamper do a little better ?!

the above simulation shows that the TREM action is pseudo linear in a very narroaw range of Cv voltages
which is just around where the bipolar transistor turn-on voltage (just below 600mV dc)

as is, I don't see the circuit doing more than a bumpy chop ...

if we could "stick" the BASE inside that range and modulate it, we might be able to get a two-sided TREM response
and this is indeed what I'm seeing if we introduce a back-bias on the 50k DEPTH pot

a simple way to do this is by biasing a grounded bipolar diode thru a (variable) resistor,
and maybe adding a fat cap to help improve AC grounding

http://www.lynx.net/~jc/LAYLAND-TREM-MODS-JCM2023.jpg (http://www.lynx.net/~jc/LAYLAND-TREM-MODS-JCM2023.jpg)

of course, the main drawback here is that when the DEPTH control is lowered so will the AC gain of the straight signal
since the back-bias provides an attenuating effect when Cv has zero AC component ...

therefore, this is not meant as a completely flexible improvement ... but rather a partial one
(ie., better shaped trem at strong settings)

btw, the back-bias can be made variable (with a rough range of 520mV to 670mV DC)
and thus playing with the resultant offset derived SHAPE becomes somewhat of a possibility as well

just some ideas to play with ...
(*!*)

Thanks chaps! Sorry about the slow reply, have had to do some repairs to my house (a local cat decided to jump off our extension roof and land on the plastic lean-to roof, at which point the plastic decided to shatter and I had to repair it - and also the gutter at the front of our house decided it was time to crack and leak water onto a bay window which makes a hell of a sound when it rains... yay, ain't DIY fun?). Anyway I made some progress, and also encountered new failures! As Dylan says, there's no success like failure!

Quote from: duck_arse on August 13, 2023, 11:02:46 AM
ohhh, I love embarrasing mistakes .....

Well have I got a super example for you! This afternoon I finally got round to picking up the circuit again, looked at the socket that holds the 100nF capacitor (C4-D4 on the vero layout) and decided to remove it (it was a recycled one) and replace it with a new one. After doing that I also switched the cables on the on OFF On SPDT switch to the original layout of them and noticed I had forgotten to put a cut on the vero at C5!!!! So I did that, added a capacitor back, turned on the circuit and guess what, I get tremolo on all three positions of the on OFF on switch! Don;t worry, I can still snatch defeat from the jaws of victory... the two settings that control which capacitor is used to remove high frequencies sound identical...  I tried a wide variety of different cap sizes in the place of C4-D4 from 1nF to 470nF and there was no change. The tremolo is different to the middle position of the switch, so there are definitely two variations in this effect, but I cannot get the third option to happen. My only thought here is that perhaps I should swap the cables attaching to the SPDT back so that they are in the order in this image? Would that enable the 100nF capacitor?
(https://i.imgur.com/zD8Ij4X.png)

Now not to outdone by this news, I then decided to switch on the loud extra boost circuit (oh the normal boost is working fine), this is the extra switch you suggested to add a 100R resistor, or my mod to switch in a 10uF - that's added with crocodile clips at the moment; your 100R suggestion is on an SPST as can be seen above. Whenever I either add my 10uF mod to the circuit and turn off your 100R switch, or just add the 100R and detach the 10uF I get awesome fuzz - even when its coming into the DI box at a non clipping volume, it sounds great except... it now has a high frequency PEEEP noise that osciallates in time with the tremolo... oh and did I say that PEEEEP was loud? My wife thought our smoke alarm was going nuts - it's about the same frequency... so ermmm help? My son says the fuzz is great, how do we get rid of the PEEEEP sound?

Quote from: duck_arse on August 13, 2023, 11:02:46 AM
which 1k resistor doesn't sound as good?

I turned it into a 100R (attached to the SPST) and that gave me the fuzz sound back. The 1K was too polite and genteel :)

Quote from: duck_arse on August 13, 2023, 11:02:46 AM
I was thinking to switch the gain-leg resistor instead of the cap as the cap would almost certainly whump each time you switched it in. the osc whump is a bonus? I suppose the 10uF across the full leg is still valid, if it does what you want. but further fiddle has muddied your results - which bits still work and which don't?

I think I've mentioned those above duck - yell if you want me to try something. I'd love the fuzz to work without the high pitch noise please! And if you have any ideas about getting the capacitors that affect the low pass filter to work that would be cool. I'm in two minds about whether I've wired that switch wrong...

Eb7+9 I will reply to you in another post soon, still trying to understand what I need to ask you - thanks for the suggestions!

Quote from: Eb7+9 on August 15, 2023, 03:14:03 PM
I think the loading on the Cv side is too low in the OP schematic ...

case in point, notice the op-amp isn't driving that side-chain node directly - but rather thru the SPEED control resistance

for one, an overly low output loading produces a squarish Cv voltage to the base of the bipolar transistor
it also prevents sufficient signal swing from forming there as well

... at least according to TINA, which i don't think is wrong here

notice also, as Rob pointed out, my inclusion of an input 10k resistor to form a voltage divider,
similar to how the Arbiter Trem-Face does it ...

https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/ (https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/)

this change allows for the potential of a more rounded TREM response
as opposed to that of a hard clamp ...

---

now, if instead we reduced this loading by increasing the side-chain resistance to around 50k (versus 5k or so as posted) two things happen:

the Cv swing increases to the point where we get (full trem) "choppy" action,
and the Cv waveform is now more triangular, what we would expect it to be in an a passive square-to-RC-expo-triangle conversion

http://www.lynx.net/~jc/LAYLAND-TREM-50k-MOD-linear-range.png (http://www.lynx.net/~jc/LAYLAND-TREM-50k-MOD-linear-range.png)

---

the question, can this passive bipolar-clamper do a little better ?!

the above simulation shows that the TREM action is pseudo linear in a very narroaw range of Cv voltages
which is just around where the bipolar transistor turn-on voltage (just below 600mV dc)

as is, I don't see the circuit doing more than a bumpy chop ...

if we could "stick" the BASE inside that range and modulate it, we might be able to get a two-sided TREM response
and this is indeed what I'm seeing if we introduce a back-bias on the 50k DEPTH pot

a simple way to do this is by biasing a grounded bipolar diode thru a (variable) resistor,
and maybe adding a fat cap to help improve AC grounding

http://www.lynx.net/~jc/LAYLAND-TREM-MODS-JCM2023.jpg (http://www.lynx.net/~jc/LAYLAND-TREM-MODS-JCM2023.jpg)

of course, the main drawback here is that when the DEPTH control is lowered so will the AC gain of the straight signal
since the back-bias provides an attenuating effect when Cv has zero AC component ...

therefore, this is not meant as a completely flexible improvement ... but rather a partial one
(ie., better shaped trem at strong settings)

btw, the back-bias can be made variable (with a rough range of 520mV to 670mV DC)
and thus playing with the resultant offset derived SHAPE becomes somewhat of a possibility as well

just some ideas to play with ...
(*!*)

Wow thanks very much for all that research! I will have to admit to you now that simple person that I am, I don't understand most of what you're telling me (sorry, you are dealing with someone who went to art college... so there are vast chunks of education that would now be useful to me that I have never encountered). If you do like Duck does, and talk s l o w l y and carefully to me as if I'm a small child (and occasionally show me shiny things to keep me excited!) then sometimes I understand stuff:) I do appreciate you are showing a revised version of the circuit that presumably can vary the LFO from square to triangle, and get a deeper, more choppy tremolo effect (those would both be cool). I think I would need to build this as a separate circuit; the vero of the current one is looking very battered and I'm worried it will disintegrate if I desolder anything else! If I drew a vero layout of how I interpret your schematic would you be able to see if that looks plausible and then I could try to build it? If I could add in a switch to cut high frequencies like I have on the above circuit then that would be cool (presumably that would go between R7 and the transistor?). I don't mind if I can't add the fuzz, that's for my son - he likes louder effects than me - if I get that working on the original circuit then he can have that one! Regarding your schematic, I have a few questions to make sure I understand it.

Vin and Vout - this is the audio in and out of the circuit?

Cv - Not sure what this is? I've heard of Control Voltage but I thought that was for modular synths? So I presume it means something else? Sorry I don't know this one... I don't have a modular synth.

Are all the pots Lin or Log? I think I've got Lins of all those types, not sure about Logs though.

Can I use a different Op-Amp? I don't have any TL071's. I have TL072, TL062, TL082, TL084 and TL074. I asume so, I just wouldn't be using the second op amp in those chips?

Thanks very much

Quote from: moid on August 17, 2023, 03:38:51 PM

Wow thanks very much for all that research! I will have to admit to you now that simple person that I am, I don't understand most of what you're telling me (sorry, you are dealing with someone who went to art college... so there are vast chunks of education that would now be useful to me that I have never encountered). If you do like Duck does, and talk s l o w l y and carefully to me as if I'm a small child (and occasionally show me shiny things to keep me excited!) then sometimes I understand stuff:)

no problem - you can always ask if something is not clear

so, to recap we can look at the LFO side of things alone first ... the bipolar transistor can be ignored

namely how the resistance level on the outside (you could call it a load I guess) affects the voltage waveform appearing there

www.lynx.net/~jc/uA741-LAYLAND-LFO-LOADING.png (http://www.lynx.net/~jc/uA741-LAYLAND-LFO-LOADING.png)

here we can see that loaded by 5k we get a choppy output waveform that is not strong enough to turn on the transistor later when we put it back in ... conversely, a 50k output load permits a waveform that almost makes it to one full volt - beyond what we need to turn on a bipolar transistor - hence the idea of sticking a pot in that circuit later

to be clear again, I'm lumping all resistors in the side circuit (including pot) into one total load resistor and seeing how the total affects the output ... all resistors in that branch form a voltage divider, thus scaling what's available at the top end

Quote
I do appreciate you are showing a revised version of the circuit that presumably can vary the LFO from square to triangle, and get a deeper, more choppy tremolo effect (those would both be cool). I think I would need to build this as a separate circuit; the vero of the current one is looking very battered and I'm worried it will disintegrate if I desolder anything else! If I drew a vero layout of how I interpret your schematic would you be able to see if that looks plausible and then I could try to build it? If I could add in a switch to cut high frequencies like I have on the above circuit then that would be cool (presumably that would go between R7 and the transistor?). I don't mind if I can't add the fuzz, that's for my son - he likes louder effects than me - if I get that working on the original circuit then he can have that one! Regarding your schematic, I have a few questions to make sure I understand it.

just be careful not to expect too much from this circuit ... as it is (stock) it's potentially a pretty choppy trem I would say
I just want to see if we can round things up a little

on the down-side the DEPTH control is meant to be close to full on (you'll see why when you breadboard it)
and it's meant to be placed right in front of your amp (usually)

producing an attenuating-only type of response // sort of like the Fender Blackface/Silverface photo-cell trems

Quote

Vin and Vout - this is the audio in and out of the circuit?

yup, it doesn't get any simpler than this ... a voltage divider, no caps = as close to noiseless as one could ever get in active electronics

my interest in this circuit is to see if we can keep it that way


tho, I know ... the temptation to provide make-up gain is there


the idea here is that providing back-bias will generate 100% output at its peak and a more (less choppy) rounded trem response
possibly a less choppy alternative to what it can do now

then, the idea is to afterwards compensate for overall perceived volume loss with the amp volume since it's a volume-reduce only circuit
again, the goal here is to try to get back as close to 100% output in the cycling so amp volume compensation is kept minimal

but let's see what you think ... I'm just guessing thru a circuit simulator named TINA

Quote

Cv - Not sure what this is? I've heard of Control Voltage but I thought that was for modular synths? So I presume it means something else? Sorry I don't know this one... I don't have a modular synth.

Cv in the modular world are typically buffered voltage sources designed to export control signals to other modules, etc ...

many guitar pedals have their own inner Control Voltages or Currents - not really meant to be exported outside to other pedals like synth modules might

a compressor and tremolo might use the same VCA or something but both have differently behaving inner Cv's (or Cc's)

in the case of this circuit, I'm defining the Cv  as the Control Voltage seen at the Base terminal of the bipolar transistor relative to ground
sorry, shoulda been more clear

btw, I mention it so you all can understand the time plots a little better // ie., see where the threshold needs to be broached

Quote

Are all the pots Lin or Log? I think I've got Lins of all those types, not sure about Logs though.

doesn't matter that much, Linear should do

Quote

Can I use a different Op-Amp? I don't have any TL071's. I have TL072, TL062, TL082, TL084 and TL074. I asume so, I just wouldn't be using the second op amp in those chips?

oh, yeah ... sorry

any op-amp should be good I'm guessing
try a uA741 if you have one ... OPA134 if you have expensive taste

same with the transistor and diode ... use what you got
it should work generally, no tight parameters here to observe

Quote

Thanks very much

good luck ...!

Quote from: duck_arse on September 25, 2022, 10:26:48 AM
(https://i.postimg.cc/44hS0Qp6/moid-tremmer.png)

like this. still centre off, spdt. as for the osc slower, you only need single pole single throw - but use a single pole double throw anyway, cause you've got those. my eyes are grinding, so I'll leave the circuit to vero translation to ..... well, anyone.

cap stays away from the base, don't be cutting there. no sleep till xmas.

Quote from: moid on August 17, 2023, 03:13:08 PM
Don;t worry, I can still snatch defeat from the jaws of victory... the two settings that control which capacitor is used to remove high frequencies sound identical...  I tried a wide variety of different cap sizes in the place of C4-D4 from 1nF to 470nF and there was no change. The tremolo is different to the middle position of the switch, so there are definitely two variations in this effect, but I cannot get the third option to happen.

see, now, this is why we want to see everything, all the time. if you look the snippet above, 80nF is your main man, all the time. switch one way shorts him, and you say that possie works, as does middle. other position adds 100nF to 80nF, so if you change the 100nF for smaller, the 80 dominates. maybe put back the 100nF, and swap in 10nF or so for the 80nF instead. then your 10 is the main man, and you add-in 100, so youse gets a bigg yumpp.

with a small tremming cap, you should get something like a shimmer instead of a great deep whumping trem.


peep peep peep - you might try fitting a 1nF cap across pins 1 and 2 of the boost opamp.

Hello chaps! Some changes / some successes / less failures :)

Firstly Eb7+9 - I will try to breadboard your circuit soon, but my breadboard is currently full of a problem LDR circuit that I need to post on the forum. I will get there! So regarding the CV part of the schematic that is just a trace / wire to ground from the base of the transistor (I thought it might be a component I needed to add). I will no doubt ask more questions soon.

Mister Duck! Once again your advice is manna from heaven and soothing to the deep oscillating thump that is my heart / circuit! So I made some changes based on your wisdom and have the following to report:

I soldered a 1nF across pins 1 and 2 of the op amp and that made the peep quieter.... but still pretty loud. So I thought, aha, a bigger cap will help! 2.2nF was quieter still but still quite noticeable, and the peep lowered it's pitch a fair bit. 3.3nF was much better - a faint thumping pulse now. 10nF got rid of any artefacts, but the downside was that when the fuzz mode was active it tamed it into a gentle overdrive... in the end my son and I played the circuit at different setings and we thought 3.3nF did the least damage to the fuzz whilst removing the majority of the thump noise. We also discovered that his guitar generates a lot less thump than mine does (his is a Squire strat, mine is a very cheap Cort guitar) so some of the problem is guitar based - my guitar has a dodgy volume pot that I keep meaning to fix... someday... I mean it makes sounds, what more do you need from a guitar? And everyone plays their guitar on volume 7-9, don't they? The other numbers are either too quiet to play with or in my case generate a Sonic Youth style random stutter kill switch effect... so mostly I play on 9. Loud enough to hear the sounds :)

Now when I say 3.3nF, that's not exactly what I have on the circuit. First of all I had to desolder a cable on the row for pin 2 and ram one leg of the 1nF in that hole with the cable and put the other leg of the cap into the same row as pin 1, and all this desoldering is causing the underside of the vero board to go black in places, which I know from long experience of screwing stuff up experimenting with circuits means that some of the copper strips will fall off soon :( So  I decided not to solder any other caps to the vero itself, but directly to the pins of the IC (yeah, that's the way I roll baby, danger is my middle name!). So I have a 1nF on the vero spanning the rows of pins 1 and 2, and also a 3.3nF on the pins of the IC itself. Does that mean that I actually have 4.3nF or is the smaller value ignored? Just so I can update the schematic correctly.

Other fun stuff that happened:
I switched the two tone caps (the 82 and the 100nF) out for 10nF (which gives a gentle but audible high frequency removal, sounds good) and after a a lot of testing, 330nF, which both my son and I liked for making a more extreme sound, but still with some high frequencies in it. 470nF cut too much out. So we have two great tone choices on the switch, which we are keeping, except now something weird has happened to the central switch setting which was the normal tremolo - it has now become really subtle, and also doesn't sound square wave much either! Both the 10nF and 330nF settings have a hard choppy tremolo and the normal tremolo is much more rounded, but very gentle. This may not be fixable with upsetting the other sounds, so I think we can live with it - if we want a 'normal' tremolo well I've got a TC Electronic Choka and that does normal tremolo fine - we will use that. We don't have a tremolo that can cut out frequencies, and that's what we are going to use this for.

Other fun things - on the 330nF setting with fuzz activated, if the rate is set to maximum and tone is 330nF it starts to sound like a weird broken 8 bit synth :) That's very cool!

To sum up; the pedal is cool and now I suspect I need to figure how to box this mess! So don't panic if there is no easy fix to bring back the 'normal' tremolo sound. Thanks very much for your patience :)

the added pins 1 and 2 cap will cut high freq gain, and the bigger the cap, the lower the cut freq. so your big peep peep cap may be killing the gain that produces your beloved fuzzings. making the opamp not burst into oscillations would be the ideal fix, but how?

when you say to junior I've made us a tremolo, does he roll his eyes? a trem peep peep fuzz 8 bit overdriving tone-cut synth?

Finally managed to box this today! One of the tightest builds I've ever made... it really should've gone in a larger box. Oh and it seems I wired the Speed pot backwards, so it's got some quirky design features (I hope I never have to open it again!) Moid Jnr was most impressed with it and has already recorded a couple of tracks, so I'll try to persuade him to do a demo of it and I'll record it for everyone's amusement. It is not a happy pedal if any other pedal goes in front of it - it does increase the thumpy noise and turns it into a higher pitched squaeak... but it's much happier on it's own! It works fine with other pedals after it.

Eb7+9 - I've found an old spare breadboard so will try to breadboard your suggestion very soon.

Hi Eb7+9

I have good news and bad news. The good news - I built your circuit design on breadboard. The bad news - it has no effect on guitar signal at all :( The guitar plays through it completely unaffected by the circuit... so presumably I screwed something up, although usually when I do that there is no audio at all... do you want me to break out the DMM or audio probe and look at any particular part of it?

Edit: Whoops forgot to say that I built this using a TL072 (because I don't have any TL071s). I did change the circuit to work with the different pinout (I'll draw a schematic for what I did later) and I'm only using one of the op amps.

Just checked the power and the brand new 9V battery I am using is putting 9.5V to the breadboard and the chip is getting 6.5V at the inverting input (leg 3 on this chip) and 9.5V on pin 8 (the power input). Where else should I check and what should I check for (volts, resistance, audio etc?)

Edit2: Just unplugged the battery and accidentally knocked my guitar over (still plugged into the circuit) and the audio volume level is exactly the same, so I think the audio is going straight from the in jack to the out jack and ignoring the circuit completely. So maybe I have misunderstood your schematic? Or this is the most transparent tremolo circuit ever :)

... fidelity is a good sign :)

what's the DC voltage at the base of the DEPTH pot ?

Measured at the Base of the Transistor it is 0V :( so that sounds problematic! It's always possible that the issue is my layout or the breadboard itself - I only have two breadboards and the other one is full of an LED / LDR circuit that I'm working on, so the one I'm using is old and I'm not sure how well it works.

And here's a schematic for you. I had to substitute a 22nF cap for your 20nF (and the TL072 for the TL071). I was a bit unsure about the line that connects the base of the transistor to ground (you called it CV?) so I just connected a cable from there to ground; maybe that is the issue? Thanks!

(https://i.imgur.com/sgNX0LO.png)

you're almost there mold ...

the speed pot needs to be rewired slightly and you need to remove the short at the Cv node
(a volt meter is placed at the Cv node in my TINA schematic in order to produce a waveform output in a real-time simulation)

and, btw - just in case - 20k was the simulation value I chose // use the original 10k speed pot value here ... or, maybe try 25k
you tell us what works best ...

(https://i.postimg.cc/LgLwpj37/sg-NX0-LO-ed.png) (https://postimg.cc/LgLwpj37)

Thanks for the fast reply - I've made your changes (removed the short and fixed the Speed pot) and I still have clean guitar going through the circuit but no tremolo :(. If I remove the power from the circuit (bypass it as it were) the signal is brighter - with the circuit powered up there is a slight loss of high end signal but sadly no tremolo. Where should I probe / DMM check the circuit next? Oh and any voltages readings will be lower from now on because guess who left the damn battery attached to the circuit last night... it's lost 1V of power since yestrerday - I assume 8.5V would still be enough to power things?

Edit: I got out my audio probe and the issue is at the start of the circuit? I can hear audio at the Jack In, and the audio is fine up to the first 10K resistor - it can be heard on the side facing the In jack, but there is no audio on the leg on the other side of that resistor... which makes no sense to me, because how does the audio get to the out jack? Very weird!

Edit2: OK just realised that there were some minor issues with where that 10K resistor was placed :-[ It is now in the right place.   The audio probe now shows audio going through the 10K resistor, which connects to the Collector of the transistor. There is audio at the Collector. There is no audio at the Base or the Emitter... I think the audio is just going direct to the out jack?.  Turning the Depth pot CW lowers the high end frequencies and makes the audio more muddy. The Speed Pot doesn't do anything as far as I can tell. The Shape Pot acts as a volume on / off pot!

Quote from: moid on September 02, 2023, 03:20:49 PM

The Speed Pot doesn't do anything as far as I can tell. The Shape Pot acts as a volume on / off pot!

great - confirmation that the back-bias circuit and transistor are together doing what they're supposed to ... what you're describing is exactly what would happen if the LFO wasn't running ... try another op amp perhaps and double check component values on that side of the circuit

Btw don't expect to see audio signal at base or emitter transistor terminals

Thanks! OK I went over the whole circuit and I found one 10uF capacitor that wasn't attached to anything (the one that connects to the Speed pot) so I got very excited and attached it correctly... but still no tremolo :( On the plus side the circuit is now capable of picking up Dutch and German radio stations... sadly Dutch or German pop / techno is not great, although the way it fizzles in and out of audible range is quite interesting, so I guess that's something? Probably caused by all the long cables I have connecting pots to the circuits (via crocodile clips). I did wonder if it was fading in and out with a tremolo effect, but I think that is just atmospheric conditions right now because it is very random - there are two stations that fade in and out and one has German announcers and the other has Dutch ones.

Do you want me to take any measurements anywhere in the circuit?

I am guessing that this circuit works by shunting the audio to ground to make the tremolo affect? Presumably the circuit makes the connection to ground more enticing to the audio than the connection to the Out jack? But at the moment something isn't working so that the more interesting connection to ground isn't happening? So I presume there should be some sort of pulse coming out of the IC that ends up in the transistor? I am going to guess that travels through the line that goes via the shape pot - so should I check for voltage or resistance on that line? And I should see a rising / falling value?

Quote from: moid on September 03, 2023, 03:28:11 PM

I am guessing that this circuit works by shunting the audio to ground to make the tremolo affect? ...

Indeed ...

In the original version it's more of a shunt ...
With the 10k resistor added it's more of a variable voltage divider

but it's nothing like a linear resistor (details omitted)

Quote

So I presume there should be some sort of pulse coming out of the IC that ends up in the transistor? I am erred to pseudogoing to guess that travels through the line that goes via the shape pot - so should I check for voltage or resistance on that line? And I should see a rising / falling value?

You got it ... the pulse that comes out of the IC is actually a square wave that is then converted to pseudo-triangle via the RC components leading to the transistor's base terminal (whose voltage to ground I call Cv)

the 33k resistor in series with 10k
Depth pot was chosen to give you a little bit of play

*BUT* the Depth control is really meant to be set full way all the time as I explained before

the fact that the Shape control works as a volume control
means you're really just one step away

Quote

so should I check for voltage or resistance on that line? And I should see a rising / falling value?

at this point you would need a scope looking at the transistor base terminal to tell anything for sure

If you want to spend another 1/2 hr on this
measure your 220k resistors to make sure, try other caps, double check power pins on op-amp...

good luck

>Off topic ON<

I'd short pin 3 & 5 and Pin 6 & 7..

>Off topic OFF<

forgot to say one thing here ...

after setting the DEPTH to 100% you'd then be hunting around with the SHAPE (diode bias) pot ...
depending on the type of taper you're using you might get lucky in a very narrow range of adjust-ability

that's assuming the oscillator is doing its thing

 ;)

Hello everyone

I will slightly cause this conversation to veer to the left for a short while - my son and I recorded a demo of the 'original' squarewave tremolo with the speed, fuzz and low pass settings, so those of you who have been on the edge of your seats ever since we finished this pedal can now breathe a sigh of relief and enjoy the below video:


I will reply to everyone else's helpful posts later tonight when it cools down a bit!

Edit: hmmm the audio sounds awful on Youtube, I will try to fix this so maybe wait until later - sorry!

Edit2:FIXED NOW! it seems our demo upset Youtube's LUFS requirements and it nuked the audio :( So I've spent a few hours learning more about Resolve than I thougth I would just to make this video sound reasonable - hope it works for you!

Quote from: antonis on September 03, 2023, 05:40:19 PM
>Off topic ON<

I'd short pin 3 & 5 and Pin 6 & 7..

>Off topic OFF<

Hi Antonis - I've done this now (thanks for the suggestion) but nothing extra happened to the circuit sadly. I've left those connctions in place because nothing went wrong when I tried them.

EDIT: Actually the volume is halved! That doesn't help much though.

Quote from: Eb7+9 on September 02, 2023, 08:55:52 PM

great - confirmation that the back-bias circuit and transistor are together doing what they're supposed to ... what you're describing is exactly what would happen if the LFO wasn't running ... try another op amp perhaps and double check component values on that side of the circuit

Btw don't expect to see audio signal at base or emitter transistor terminals

I just tried a TL082 chip in place of the TL072 (they seem to have the same pinout) but no joy there :(

Here's the voltage for the chip (currently a TL082)

Pin 1  8.2V
Pin 2  2.1V
Pin 3  8.1V
Pin 4  0.01mV
Pin 5  8.1V
Pin 6  1.6V
Pin 7  8.1V
Pin 8   8.81V

Does any of that look weird? To me it seems odd that 6 and 7 (which are currently tied together are completely different values... I'm not using either of those pins, but that looks odd to me. I wonder if this breadboard is wrecked and that's why things aren't working?

You probably tied toghether and to Vref unused pins wrongly.. :icon_wink:

pin 5 to Vref (pin 3 or any convenient point)  and pins 6 & 7 shorted..

P.S.
"Something" messed up the whole bias configuration.. :icon_wink:
Pin 3 (and 5 after shorting) should measure half-supply voltage..
Your op-amp is heavily saturated..

Hello everyone
Sorry about the delay in replying, I had to go back to work this week... so progress has been slow. For extra fun we are having a heatwave - it is 31C today, I am not sure if I should melt or evaporate. So of course it seems like perfect time to sweat over hot breadboard! I decided to completely rebuild the circuit from scratch... and it still doesn't work. It behaves identically to how it did before, with the only change being when I add Antonis' shorts to the circuit the audio is slightly distorted - not louder, just clipping. I measured the TL072 chip voltages and did without the shorts and with the shorts:

No shorts
Pin1.  4.9V
Pin2.  1.49V
Pin3.  5.6V
Pin4.  0.8mV
Pin5.  1.04V
Pin6.  1.067V
Pin7.  1.41V
Pin8.  8.8V

With Antonis' shorts
Pin1.  5.1V
Pin2.  1.49V
Pin3.  5.6V
Pin4.  0.3mV
Pin5.  5.6V
Pin6.  5.6V
Pin7.  5.6V
Pin8.  8.8V

Antonis - I think that shows the voltages you were expecting with your shorts added? So presumably the fault is somewhere else in the circuit? Any idea where I should look or what to look for? Hope you are all somewhere cooler!

Quote from: moid on September 05, 2023, 09:54:58 AM

I just tried a TL082 chip in place of the TL072 (they seem to have the same pinout) but no joy there :(

let's back track a bit ...

first of all, don't short op-amps together like Antonis stated
that's complete non-sense

the oscillator isn't oscillating obviously
just focus on getting the oscillator going

I'm assuming you don't have a scope
and measuring DC voltage on an astable circuit that's supposed to oscillate is again complete non-sense

what you should do is stick an LED and 10k resistor between pin-1 (output) of op-amp and gnd
THIS will tell you if you oscillator is doing anything // what it's supposed to ...

ie., square wave = on // off // on // off

ignore the rest for now ...

it's the same oscillator circuit as what you have in your box
if you made it work once you should get it to work twice

exactly the same way ...

Quote from: Eb7+9 on September 09, 2023, 11:28:20 AM
first of all, don't short op-amps together like Antonis stated
that's complete non-sense

Antonis just proposed the dedicated wiring for not used op-amps..
(non-inverting input at Vref and inverting input & output shorted..)

(https://i.imgur.com/3fplvlW.png)

If that is non-sense, put the blame on various op-amp manufacturers..
(my 2 cents..)

Quote from: moid on September 09, 2023, 09:49:20 AM....I am not sure if I should melt or evaporate....

No choice here. It is 100% relative humidity now. The afternoon may get as dry as 95%RH. Then the rain starts. We'll have NO evaporation for a while. (The grass clippings I mowed 2 days ago are still fresh and green.)

In the western desert, Las Vegas is 16% RH but 102 degrees F (39C) at dusk, so melting is mandatory.

I thought Antonis was recommending doubling on everything -my bad

must be a simple issue like input swaps

Quote from: PRR on September 09, 2023, 09:27:27 PM

No choice here. It is 100% relative humidity now. The afternoon may get as dry as 95%RH. Then the rain starts. We'll have NO evaporation for a while. (The grass clippings I mowed 2 days ago are still fresh and green.)

In the western desert, Las Vegas is 16% RH but 102 degrees F (39C) at dusk, so melting is mandatory.

Yikes, I will stop complaining! Thankfully it rained a bit today so we have a mild 24C now, but much humid, hopefully tomorrow will be cooler still. At least it meant I could focus on this circuit a bit.

Eb7+9 - sadly I don't have a scope, but thanks for your cool probe suggestion! I have kept Antonis' shorts in and made a little LED and 10k probe and started sticking it into the circuit - I think the issue is between a 10uF capacitor and the 33k resistor - the LED turns off if I touch the ground leg of the cap or the 33k resistor leg that connects to the cap. I tried substituting the capacitor for another of the same value and got the same result - it seems to me that the capacitor is stopping the flow of electricity. That said, there is no evidence of a pulse anywhere in the circuit - the LED is either on or not. I have tried this with the Speed pot at minimum and maximum sweep, the only difference is the LED is less bright when the speed pot is at CCW.

Pin1 light on
Pin2 light off
Pin3 light on but dim
Pin4 light off
Pin5 - 8 light on

The LED is on from pin1 to the speed pot, it works up to the long leg of the 10uf cap at the top of the schematic, but nothing gets past that leg. The other 10uF cap is fine on its long leg, with no light on the stripe side of the cap. Does any of this make any sense?

Quote from: moid on September 10, 2023, 01:03:26 PM
it seems to me that the capacitor is stopping the flow of electricity.

Partially true.. :icon_wink:

Could we have a final schematic, plz..??
(not something like the one with permanently grounded Base of BJT..) :icon_biggrin:

Yes, I realise now I said that about the capacitor that the statement is a bit obvious... however I'm pretty sure that the cap should discharge some electricty every now and then (maybe a few times a second) so that the circuit can work! I don't think it is doing anything.

Here is an uptodate schematic. The guilty capacitor is labelled at the top of the schematic. I have tried swapping it for other 10uF caps but there is no difference.

(https://i.imgur.com/eQHrRz4.png)


By the way, sorry for the slow updates, work has started up again and I've not had much time to look at this circuit (and I was able to build and finish a totally different circuit on the side - the Memory Loss-a-like, based on the Seppuku FX pedal of the same name and it's great fun to play with). Back on this one now, not getting distracted by anything else... oh hello park autowah, well how have you been?

Thanks for the help!

Thanks for your update ...

personally I don't think wiring up the second op amp is necessary or even a great idea ... I would try working with one side only and let the other side clamp to either rail - it's generally no biggie ...

wondering if your 10uF caps might be exceptionally leaky ??
try turning them around

have you got any film caps in that range ?!

also, the 20nF cap is the one that really gets the ball rolling so to speak
try a 100nF film instead if you have one

Thanks for replying so quickly!

I tried some of your suggestions - swapped the 22nF with a 100nF - made no change, the LED probe does not light up after the ground leg of the 10uF capacitor.

I removed the shorts (pins 6-7 and pins 3-5). no change, I've left them off for now.

I tried a different brand of 10uF capacitor (same result).

I then swapped the 10uF around so that the stripe/ground faces towards the IC part of the circuit and the LED probe lights up on the other leg - so electricty is now going through the cap. The LED stay lit brightly until it hits the 33K resistor. After the resistor, the LED is still on but noticeably dimmer. The LED light probe lights up to Lug 1 of the depth pot as long as the pot is fully CW. If I put the LED probe on Lug 2 or 3 the LED turns off. on Lug1 if I turn the pot back to CCW, the LED dims and turns off and no setting will allow anything to happen to Lug2 which is weird; I would expect some voltage to appear there and light up the LED? Is the Pot too strong, maybe I should try a smaller pot? OK just tried a 1K pot and there was no effect, except that when sweeping the pot, there was a gentle slow fading of the audio from off (full CCW) to on (full CW). With the 10K pot the audio is off until near full CW when it suddenly turns on. No tremolo of course. When I put the LED probe on lug 1 of the 1K pot the LD remains off which is odd. With the 1K pot in place the LED does not light up if I touch the 33K resistor on the side facing the pot. If I put the 10K pot back I do get a lit LED at that point. Electricity is bloody weird!

Should I try a bigger pot?

I don't have any film caps of 10uF size (I didn't realise you could get such a thing; I thought they stopped at 1uF and everything was electrolytic on any number higher than that?). I have found them online - they are really expensive - I will order some if you think that is the solution.

> film caps of 10uF size (I didn't realise you could get such a thing; I thought they stopped at 1uF and everything was electrolytic on any number higher than that?)

You can get film "any" value you want to pay for. If you build an atom bomb you may want very large low-loss caps. That's how one ban-busting bomb project was uncovered, the cap supplier thought the order was funny.

10uFd is actually a reasonable value if you actually "needed" film. (You don't).

Panasonic ECQ-E1106KFB
10uFd
Voltage Rating - DC  100V
Polyester, Metallized
Size / Dimension  1.024" L x 0.453" W (26.00mm x 11.50mm)
Height - Seated (Max)  1.024" (26.00mm)
$3.27 at Digikey

Or for "more!", try MMP0100F33
(1,100uFd 600V)
CAP FILM 1151.3UF 480VAC RADIAL
Cornell Dubilier Electronics (CDE)  1 : $1,060.50

For pedals you could use a 16V e-cap costs like $0.33 each and smaller than a pencil eraser.

Quote from: moid on September 17, 2023, 06:20:35 PM
Thanks for replying so quickly!

I tried some of your suggestions - swapped the 22nF with a 100nF - made no change, the LED probe does not light up after the ground leg of the 10uF capacitor.

I removed the shorts (pins 6-7 and pins 3-5). no change, I've left them off for now.

I tried a different brand of 10uF capacitor (same result).

I then swapped the 10uF around so that the stripe/ground faces towards the IC part of the circuit and the LED probe lights up on the other leg - so electricty is now going through the cap. The LED stay lit brightly until it hits the 33K resistor. After the resistor, the LED is still on but noticeably dimmer. The LED light probe lights up to Lug 1 of the depth pot as long as the pot is fully CW. If I put the LED probe on Lug 2 or 3 the LED turns off. on Lug1 if I turn the pot back to CCW, the LED dims and turns off and no setting will allow anything to happen to Lug2 which is weird; I would expect some voltage to appear there and light up the LED? Is the Pot too strong, maybe I should try a smaller pot? OK just tried a 1K pot and there was no effect, except that when sweeping the pot, there was a gentle slow fading of the audio from off (full CCW) to on (full CW). With the 10K pot the audio is off until near full CW when it suddenly turns on. No tremolo of course. When I put the LED probe on lug 1 of the 1K pot the LD remains off which is odd. With the 1K pot in place the LED does not light up if I touch the 33K resistor on the side facing the pot. If I put the 10K pot back I do get a lit LED at that point. Electricity is bloody weird!

Should I try a bigger pot?

I don't have any film caps of 10uF size (I didn't realise you could get such a thing; I thought they stopped at 1uF and everything was electrolytic on any number higher than that?). I have found them online - they are really expensive - I will order some if you think that is the solution.

sorry, I typed without thinking carefully ... I meant any better caps, like BP electros ...
but the circuit shouldn't be that finicky anyway

strange - like, you've already made this LFO work before right ?

yes, electricity can seem weird ...

btw, the 10k+LED "probe" is only meant to go between op-amp output and ground
making sure to orient LED properly (try swapping it around)


are you by chance tying pins 1 and 8 together ? ... you know, the way the schem is drawn almost looks like it
only thing else I can suggest is measuring those 220k resistors

otherwise, who knows ...

ok, that's enough torture - thx for trying this little idea out
8) 8) 8)

Leyland pedals?  As in British Leyland cars, famous for using Lucas Prince of Darkness electricals?  No wonder trying to make it work is a six-page thread already.

Quote from: amptramp on September 18, 2023, 07:51:06 AM
famous for using Lucas Prince of Darkness electricals?

Pure nightmare..!!! :icon_frown:

Quote from: amptramp on September 18, 2023, 07:51:06 AM....a six-page thread already.

Six? I see three. AH! There is an option. Profile, Modify Profile, scroll, Messages per page: Default is 20 but a single side-drift can go that far and still return to topic! 50 means more to track but all on one page.
(https://i.postimg.cc/VSwGJ44y/50perpage.gif) (https://postimg.cc/VSwGJ44y)