Leyland Pedals Ultra Simple Tremolo layout and some questions...

[moid]

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?)

[ElectricDruid]

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.

[moid]

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.

[moid]

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

[duck_arse]

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.)

[moid]

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.

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.

(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!

[duck_arse]

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.

[moid]

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?

see your wrong, unmoved layout?

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

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?

[duck_arse]

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.

[moid]

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?

[duck_arse]

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.)

[moid]

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?





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

[ElectricDruid]

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?!?

[moid]

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

[duck_arse]

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.

[moid]

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



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

[Rob Strand]

And 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.

[moid]

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

[moid]

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

[duck_arse]

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