Tri-Vibe switch pop only in Whirl or Swirl modes

[midwayfair]

Schematic:
http://www.runoffgroove.com/tri-vibe.html

Apologies for lack of pictures -- the one I'm working on right now is Solderman's layout ...
http://solderman.fatabur.se/Tri%20Vibe/Tri-Vibe%20Project%20file.pdf
... and getting it into and out of the box is *very* annoying. This layout includes a 1M pulldown resistor preceding the input cap, which stops the pops in vibe mode.

I've got another copy on the runoff groove perf, which does the same thing, so I'm confident it's not a wiring, part, or switch issue.

Anyway, I get a pop when turning on (but not turning off) and ONLY when it's in the swirl or whirl modes, which connect the signal from pin 1 of the input op amp to pin 6 of the output mixer. I'm unable to locate any DC offset.

So far as I can tell, the difference here is that these paths have essentially no input cap of sorts between the output of the preceding op amp and the input of the following. However, I can't understand how that would create a switch pop when there's a buffer in between the change.

Can anyone think of anything that might silence this switch pop? Possible a medium sized cap at lug 1 of the toggle switch?

[midwayfair]

Actually, it pops in all three modes, it's just quieter in vibrato mode. Hrm.

[B Tremblay]

Jon, I'm sorry that you've encountered a frustrating situation with the circuit.  I just checked mine (on perf) and I didn't hear a pop with any of the three mode settings.

It may be a royal pain to do this, but try putting a 1M or larger resistor between the center lug of the switch and junction of the 47k - 100k resistors (effectively between pins 1 and 6 of IC1).  That will still block dry signal in Vibe mode, but will hopefully equalize any difference in voltage when switching.

[midwayfair]

Jon, I'm sorry that you've encountered a frustrating situation with the circuit.  I just checked mine (on perf) and I didn't hear a pop with any of the three mode settings.

It may be a royal pain to do this, but try putting a 1M or larger resistor between the center lug of the switch and junction of the 47k - 100k resistors (effectively between pins 1 and 6 of IC1).  That will still block dry signal in Vibe mode, but will hopefully equalize any difference in voltage when switching.

Hrm. That helped a very small amount, but not enough to unbox the little one (I'm making the potential mods on the big one since the board is facing up.)

It's not a huge issue, and it's not LOUD, certainly nowhere near the level of the dry signal. But it is puzzling that it happened on multiple layouts. I might build one more board (on a PCB).

If I really, really, really needed to fix it for a recording or something that required me to turn it off and on, I would just make a JFET buffered bypass.

[B Tremblay]

What are the pin voltages and part number for IC1?

[midwayfair]

What are the pin voltages and part number for IC1?

NE5532

Voltage:
1/2: 4.28
3: 3.88
4:G
5-7: 4.5
8: 9.08

These look normal to me.

[B Tremblay]

The only thing I can think of is a leaky output cap.

Is there any change in the pin 6 voltage in different modes?

[midwayfair]

The only thing I can think of is a leaky output cap.

Is there any change in the pin 6 voltage in different modes?

Actually, I think this is "solved" in some manner ... it seems like every single TB pedal I have has started popping in isolation or in a chain. I was playing through my main board this morning and everything I turned on or off popped. So apparently this is not a tri-vibe issue.

Sorry for wasting your time, B.

Now to figure out what the heck is going on with my amp.

[deadastronaut]

hi jon, i just solved an issue with a switch 'pop'

i was switching between 2 caps, and pop...pop...

i put 2 X  1M resistors on the switch lugs.  (1M-10M)

lug>>>resistor>>>lug>>>resistor>>>lug

very quiet now...hope this helps.

[B Tremblay]

Actually, I think this is "solved" in some manner ... it seems like every single TB pedal I have has started popping in isolation or in a chain. I was playing through my main board this morning and everything I turned on or off popped. So apparently this is not a tri-vibe issue.

Sorry for wasting your time, B.

Now to figure out what the heck is going on with my amp.

My time was not wasted at all!  I am glad that you have made progress with the investigation and hope that the cause presents itself quickly.