Switch click in the delay line

[mark2]

So with any of a few variations of an FV-1 circuit, I get a slight click sound when engaging the pedal.  With a delay patch running it repeats the click making it much more pronounced and unusable.

Is that purely mechanical, or do you think there could be something about the circuit that can be improved? This happens with the Arachnid from Pedalpcb for example, so that's included below.

When I replace the 3PDT latching foot switch with a relay I still get a slight thump sound. I'm not yet sure if I traded one sound+problem for another, or if it's the same one persisting.

[Digital Larry]

How do you have the switch connected?  Most switching pops can be minimized by making sure that the DC voltage on switch pins is the same whether switched in or out.  Generally this involves placing very large resistors (e.g. 10 meg) across coupling capacitors that would otherwise possibly be left floating on one end..

[mark2]

In the 3pdt version it was just wired up like a common true bypass. e.g like the first one here http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html

Do you have an example of what you mean I can take a look at?

[mark2]

That is, assuming you mean something besides the R1+C1, and R11+C15 pairs. 

Edit: and if it helps, I measured the DC voltage at the PCB's input and output when bypassed and it's reading exactly zero.
I also tried increasing the input series resistor (R22) to 150k (arbitrarily large) to see if it reduced any sound from switch bounce, but no such luck.

[anotherjim]

If you disconnect the status LED from the footswitch, does that stop the noise?

And, not one ceramic power bypass cap on that board despite it being mandated in every IC datasheet.

[idy]

Yes, the R1 and R11 are the "pulldowns" to minimize pops, they are appropriate. And your bypass wiring if it is like the diagram grounds the input in bypass, a further help.

Sometimes 3pdt are microphonic, you tap with a pencil (or your foot) and you hear a sound through your amp. Other components can also be microphonic, notoriously ceramic caps. And yes, disconnecting the LED is good to try.

One more thing to eliminate:pedal ventriloquism. Your amp or some other effect does have voltage leaking and that causes the pedal to pop. Need to check voltages on the amp, need to test with nothing else in the path.

[mark2]

If you disconnect the status LED from the footswitch, does that stop the noise?

And, not one ceramic power bypass cap on that board despite it being mandated in every IC datasheet.

Yeah, I still get the problem with the LED disconnected unfortunately

I'll try pulling out the ceramic bypass caps.

[mark2]

One more thing to eliminate:pedal ventriloquism. Your amp or some other effect does have voltage leaking and that causes the pedal to pop. Need to check voltages on the amp, need to test with nothing else in the path.

I tried checking the DC voltage at the input and output while it was hooked up, and it was exactly 0. I also tried it with nothing else in the signal chain.

I believe it's something in the pedal circuit unrelated to the switching.

[deadastronaut]

mark, have you tried the 3pdt no pop, jacks amz thing?

i use this all the time, no pops, 

i use the 2nd diagram down.


http://www.muzique.com/lab/led.htm

[mark2]

mark, have you tried the 3pdt no pop, jacks amz thing?

i use this all the time, no pops, 

i use the 2nd diagram down.


http://www.muzique.com/lab/led.htm

I took the simpler route and just unhooked the LED.
It didn't fix it, but yeah I plan to add it to the next iteration of PCBs just to avoid a new issue.

[antonis]

Try to ground, via a high value pull-down resistor, each 1μF cap  till you find the guitly one..

[anotherjim]

If you disconnect the status LED from the footswitch, does that stop the noise?

And, not one ceramic power bypass cap on that board despite it being mandated in every IC datasheet.

Yeah, I still get the problem with the LED disconnected unfortunately

I'll try pulling out the ceramic bypass caps.

Don't! I was saying there aren't any! Or are there? They aren't shown on the schematic. There should be some but they are often left out.

[mark2]

Try to ground, via a high value pull-down resistor, each 1μF cap  till you find the guitly one..

I'll try that, thanks.

[mark2]

Don't! I was saying there aren't any! Or are there? They aren't shown on the schematic. There should be some but they are often left out.

Ahh, I clearly misunderstood.

No, there are some MLCC and SMD caps next to the necessary pins on the FV-1. If not on the one shown above, then on the other one I've been testing with. Shown below.

[mark2]

Try to ground, via a high value pull-down resistor, each 1μF cap  till you find the guitly one..

I'll try that, thanks.

By the way, is it the type (mostly mlcc) or the size or the placement than makes you think these?

Any in particular that seem most susceptible ?

[antonis]

Any signal path series cap (DC "floating") is suspect..
Priority given to In & Out ones..
And yes, size DOES matter..

[mark2]

Great,will do. Thanks to you and everybody for your help.

And for future reference, if adding a path to GND for one of the caps gets rid of the pop, do I just leave it there as a solution? Any downside other than adding a high pass filter? Or does there exist a better solution once the culprit is identified?

[mark2]

Unfortunately grounding each of the caps seemed to make no difference.

The noise on the relay version is already really quiet, so perhaps I'm up against diminishing returns already. I also have a backup plan to toggle the patch on the FV-1 immediately after switching to kill any echos (dump memory and reload patch).

That said... If anyone knows somebody who might be interested in doing a small consulting job on this (preferably US-based) please let me know. I'd love to ship one to somebody else to give it a once over and see what they can find.

[antonis]

Just a last attempt..

Wire 3PDT switch like below wiring diagram..


It has OUT grounded, also..
(despite 100k shunt resistor)

[mark2]

It has OUT grounded, also..
(despite 100k shunt resistor)

Thanks for yet another good idea to try. Unfortunately it didn't seem to help.  I only tried it with the latching foot switch version since I don't have any 3-pole relays, but it sounded the same as the foot switch without a grounded output when bypassed.

What an elusive bugger.