New at runoffgroove.com: Tri-Vibe

[doc_drop]

Hi guys,

Bump de Bump, Bump...I did some more tests with my build, and would like to report my results. Hopefully someone can give me a tip on where to start looking based on these.

First the symptoms:

I am getting a vibe-ish effect on the whirl and swirl settings. It is uneven in that it has one pulse that is weak and another that is strong. This repeats. There is also a very fast transition between more of a tremelo effect and no effect at all when I adjust the depth knob. It is almost like there should be some clean signal mixed in with effected signal, but the clean is either missing or on full depending on the depth pot.

In the vibe mode I get almost no sound at all. If I crank the depth, I get a faint clicky little sound, but almost nothing.

Here are my #'s:

Voltages:

Filtered/regulated wall wart: 9.29v

But first odd thing, the 9.29v is without being connected to the circuit. Once it is connected it drops to 8.88v. Then the pin 8's on the IC's are only getting 5.8-ish volts. Is that normal?

Anyway:

IC1
Pin 1 2.89v
Pin 2 2.9v
Pin 3 2.89v
Pin 4 7mv
Pin 5 2.9v
Pin 6 2.9v
Pin 7 2.3v (alternates a bit)
Pin 8 5.84v

IC2
Pin 1 2.9v (alternates a bit)
Pin 2 2.9v
Pin 3 2.9v (alternates a bit)
Pin 4 7mv
Pin 5 2.9v
Pin 6 2.9v
Pin 7 2.9v (alternates a bit)
Pin 8 5.83v

IC3
Pin 1 2.9v
Pin 2 3.3v (alternates a bit)
Pin 3 2.7v
Pin 4 7mv
Pin 5 2.9v
Pin 6 2.9v
Pin 7 2.9v (alternates a bit)
Pin 8 5.82v

IC4
Pin 1 1v
Pin 2 3.5v 
Pin 3 3v
Pin 4 2.97v
Pin 5 1.37v
Pin 6 8mv
Pin 7 1.37
Pin 8 8mv
Pin 9 3.8v
Pin 10 4.5v  (alternates a bit)
Pin 11 5.8v  (alternates a bit)
Pin 12 4.5v (alternates a bit)
Pin 13 2.99v
Pin 14 3v
Pin 15 3.5v
Pin 16 1v

Thanks for any help you can offer!

[frequencycentral]

Filtered/regulated wall wart: 9.29v

But first odd thing, the 9.29v is without being connected to the circuit. Once it is connected it drops to 8.88v. Then the pin 8's on the IC's are only getting 5.8-ish volts. Is that normal?

That can't be right. Something is dragging your +ve down. Check out the schematic, there's a 22R resistor bottom left, where power enters the board, if you're getting 8.88v one side of it and 5.8v the other side you must have a short somewhere I would have thought. Are you sure your 22R is 22R?

[doc_drop]

Hmmm. Thanks Rick. I didn't like the looks of that either...

I do believe the resistor is correct, although I will quadruple check it to be sure. I bet you're right that there is a short. I'll poke around again and see if I can find it. (I already have more than once, but I want this thing to work, so I am willing to give it another go around.)

Anybody else?

[B Tremblay]

Rick is correct, +V is low.  Also, check around pin 8 of U4.  That should be close to the same voltage as pin 9, both of which should be close to Vref (4.5v).

[doc_drop]

Thanks B.

Interesting about the #8 pin. It looks like mine is connected to ground somehow. Wow, there must be some really obvious screw up and hopefully knowing about pin #8 will help me find it.

Thanks 1,000,000!

[trjones1]

Ok, this may be a stupid/basic/pointless question, but is there any reason I can't split up the op amps in the tri-vibe.  I.e. use one dual opamp for U2a and U3a and another for U2b and U3b?  I'm working on a vero layout and it would just work out better this way.  If I can do this, is there any reason I couldn't add U1 into the mix, since it's in the audio path?  Thanks.

[B Tremblay]

An official PCB layout, created by John Lyons, has been added to the Tri-Vibe project: http://runoffgroove.com/tri-vibe.html

Please note that the schematic (and perfboard layout as well) has been updated.  The input and output caps of the mixing stage (U1b) were corrected.  The 1uF nonpolarized cap is now 220n and the notation of the output cap polarity was backwards.  Apologies for this oversight.

[B Tremblay]

Ok, this may be a stupid/basic/pointless question, but is there any reason I can't split up the op amps in the tri-vibe.  I.e. use one dual opamp for U2a and U3a and another for U2b and U3b?  I'm working on a vero layout and it would just work out better this way.  If I can do this, is there any reason I couldn't add U1 into the mix, since it's in the audio path?  Thanks.

The two opamps forming the LFO should correspond to the same IC, like U2a and U2b.

...is there any reason I couldn't add U1 into the mix, since it's in the audio path?  Thanks.

I'm not entirely certain of what you're asking, but the audio stages should be kept separate from the LFO stages.

[Andre]

An official PCB layout, created by John Lyons, has been added to the Tri-Vibe project: http://runoffgroove.com/tri-vibe.html

Please note that the schematic (and perfboard layout as well) has been updated.  The input and output caps of the mixing stage (U1b) were corrected.  The 1uF nonpolarized cap is now 220n and the notation of the output cap polarity was backwards.  Apologies for this oversight.

I believe to see a vague resemblance between my original layout and "John Lyons" layout.  

[~arph]

 

Yeah it'd be nice if he'd credited you.

[flo]

Yeah i'd be nice if he'd credited you.

+1

[John Lyons]

Andre
You are correct. I meant to credit you.
I worked on an initial layout for hours
but cornered myself in in a couple places
so I scrapped it...
I used your layout and moved a few things around
to fit with my larger traces and pads etc.
I'm sorry if I stepped on your toes...

I'll put your name on the layout.

John

[doc_drop]

O.K. I got it to work. It wasn't instant gratification, though. 

Last night I checked around pin #8 on IC4. Lo and behold I had connected it to ground. I disconnected and was hoping to have a working circuit, but no luck. The LFO no longer pulsed. I knew not only from the sound, but also because I have a rate LED on it. So, I got a little discouraged and went to bed. Around 3:00AM I woke up thinking, "That's right, I had connected pin 8 to ground because the LFO only worked that way." But obviously it didn't do the circuit any good...Then I remembered that I got the LFO to work on the breadboard by replacing IC3 with a NE5532. So, this morning I replaced IC3 again, and I have a wonderful sounding circuit, especially when I run it at 12v like I normally do.

That sine wave LFO is sweeeeet. And I like the swirl and whirl modes a lot!

So Thanks B and Rick. For the circuit and the help!

My last 2 circuits, this one and Nurse Quacky, will only work with NE5532's. I don't know what to make of it, but I will keep it in mind!

But now I read my mojo cap is too big? I think I might just leave well enough alone...

[B Tremblay]

O.K. I got it to work. It wasn't instant gratification, though.  ... So Thanks B and Rick. For the circuit and the help!

I'm happy to hear that your build is now working.

[doc_drop]

I'm happy to hear that your build is now working.

Me too!

Out of curiousity, does the 1uF to 220nF change to the output cap have an effect on the frequency range of this guy? Why did you make that change?

[stm]

The 220nF/47k pair has a low frequency corner of 16 Hz, so it is more than adequate for guitar and bass signals.  For those who already built the circuit using 1uF there is no need to change the capacitor to 220nF.

Initially, the circuit was breadboarded with 1uF for availability, however 1uF caps are generally larger and not in everyone's parts bin, so it makes sense to reduce its value as it still does its job properly.  Coincidentally, the input stage has a 10nF/1M pair which also has a 16 Hz low frequency corner.

[salwa]

Hi!
I've just finished building Tri-Vibe using layout from ROG. It works, but with some issues. First of all, I hear strong LFO ticking when Depth pot is turned to maximum or somewhere nearby. Any idea what may be the cause? Second thing - Swirl and Whirl settings causes circuit to work rather like tremolo than anything else. But it's not that important, I can live with it. But the ticking is ruining this circuit for me. I'm using LM13600N chip, TL062's and TL072.

[solderman]

Hi ROG

Thank's for a really terrific circuit.

Q: Is there any reason why I cant use a normal voltage divider Rx/Rx+C for Vref instead of U2a setup. The reason is that I'm, as usual, trying to get this one to fit in a 1950A box and all "cut corners" when creating the PCB layout is welcome.

I plan to use 0one quad OP Amp for the LFO and a singel for the audio part. One reason I don't want to use the U2a is that I don't want to mix the LFO +V power rail with Vref to eliminate ticking etc. and to cut the legs under U2a to ease trace routing. 

[stm]

Hi ROG

Thank's for a really terrific circuit.

Q: Is there any reason why I cant use a normal voltage divider Rx/Rx+C for Vref instead of U2a setup. The reason is that I'm, as usual, trying to get this one to fit in a 1950A box and all "cut corners" when creating the PCB layout is welcome.

I plan to use 0one quad OP Amp for the LFO and a singel for the audio part. One reason I don't want to use the U2a is that I don't want to mix the LFO +V power rail with Vref to eliminate ticking etc. and to cut the legs under U2a to ease trace routing.  

Unfortunately the active Vref is there for a reason: the LM13600 with its 470R biasing resistors and the 3k9 diode resistors do require a solid reference voltage since they provide some current that must be dealt with.  When using a 10k+10k resistive divider I recall the reference voltage was raised above 4.5V.  You could either reduce the divider resistors and eventually change the value in one of them so as to keep Vref at 4.5V, but this is something not recommended as it will increase current consumption and won't be as stable.  If Vref is away from 4.5V the dynamic range will suffer and sound might degrade.  Take notice that even if you could do without an active Vref, there is no other opamp you could omit in there, so you would still end with a spare opamp.

If I had the "must" to go into such a small enclosure, I'd do the following:

1) use SMD versions of the opamps and LM13600
2) use 1/8 watt resistors and as small capacitors as I could get (non-SMD)
3) Use a dual layer PCB

This is perfectly possible using a normal soldering iron, however it might become more expensive in terms of the bill of materials.

[stm]

Hi!
I've just finished building Tri-Vibe using layout from ROG. It works, but with some issues. First of all, I hear strong LFO ticking when Depth pot is turned to maximum or somewhere nearby. Any idea what may be the cause? Second thing - Swirl and Whirl settings causes circuit to work rather like tremolo than anything else. But it's not that important, I can live with it. But the ticking is ruining this circuit for me. I'm using LM13600N chip, TL062's and TL072.

The LFO in this circuit does not tick if properly built.  A 10n+100k couple around pins 1 and 2 of U3a prevent ticking by reducing the slew rate during transitions.  As you report the circuit is actually ticking and two modes are not working as expected, it is clear that there is something wrong with your build.  I suggest you do a thorough revision (once again) looking for shorts, wrong connections, wrong part values, etc. and post the voltages on every pin.