Red Llama popping - tried every trick I could think of.

[Bishop Vogue]

Looking for anyone who has experience with hunting down causes of popping.  I've tried everything I could think of, including pulldown resistors, small value resistors between the power and the board, Orman's LED pop-fixer, checking for microphonic capacitors and even switching the switch itself.  I'm out of ideas.  If anyone can help, I'd sure appreciate it. Thanks, all.

[ElectricDruid]

It certainly sounds like you've covered the usual stuff.

Are you certain it's coming from the pedal itself? DC offsets from upstream can cause horrible pops...

T.

[Mark Hammer]

Is it being used in conjunction with a commercial pedal that uses a momentary switch?  If so, you may be experiencing "pedal ventriloquism".  This is a phenomenon in which a player adds a true-bypass  pedal to an already quiet functional pedalboard.  Since the existing pedals are e-switched, they are not compensated for momentary disconnection and reconnection of their inputs (which TB will do).  Sticking a TB pedal ahead of an e-switched pedal results in popping from the e-switched pedal's input, but the player mistakenly attributes it to the new TB pedal, because they can plainly see that the e-switched pedal can be turned on and off repeatedly without any popping, but the moment the TB pedal is switched you hear pop.

THAT's why I term it pedal ventriloquism.  The e-switched pedal is like the ventriloquist throwing their voice so that it appears to come out of the dummy, which is the new pedal in this case.

The cure?  Simply install a 1M-2M7 resistor between hotand ground on the input jack of the pedal that comes after the TB pedal.

[digi2t]

Is this a production pedal, or clone circuit?
Can you post the schematic and layout that you're using?
What size filter cap are you using between power / ground, and pin 1 of the 4049?

[Bishop Vogue]

Thanks for all these great replies.  I'm using the 'clone' of the Red Llama  (the llama itself is a clone of the Tube Sound Fuzz, as I'm sure you guys know).  The pedal is alone - no others in a chain.  Not my power supply either - a customer returned it to me for service, so the problem has happened in several locations and setups.  Here's a link to the layout:

http://tagboardeffects.blogspot.ca/2012/06/way-huge-red-llama.html

[Bill Mountain]

Is it being used in conjunction with a commercial pedal that uses a momentary switch?  If so, you may be experiencing "pedal ventriloquism".  This is a phenomenon in which a player adds a true-bypass  pedal to an already quiet functional pedalboard.  Since the existing pedals are e-switched, they are not compensated for momentary disconnection and reconnection of their inputs (which TB will do).  Sticking a TB pedal ahead of an e-switched pedal results in popping from the e-switched pedal's input, but the player mistakenly attributes it to the new TB pedal, because they can plainly see that the e-switched pedal can be turned on and off repeatedly without any popping, but the moment the TB pedal is switched you hear pop.

THAT's why I term it pedal ventriloquism.  The e-switched pedal is like the ventriloquist throwing their voice so that it appears to come out of the dummy, which is the new pedal in this case.

The cure?  Simply install a 1M-2M7 resistor between hotand ground on the input jack of the pedal that comes after the TB pedal.

Mark is spot on as usual.

This is one of the more common issues I come across with my builds.

Here's another article about it:

https://www.mrblackpedals.com/blogs/straight-jive/6629778-what-really-causes-switch-pop

[antonis]

Here's another article about it:
https://www.mrblackpedals.com/blogs/straight-jive/6629778-what-really-causes-switch-pop

In a very personal way of thinking.. 

P.S.
Haven't seen anyone suggesting 3PDT switch IN & OUT grounding..

[R.G.]

Thanks for all these great replies.  I'm using the 'clone' of the Red Llama  (the llama itself is a clone of the Tube Sound Fuzz, as I'm sure you guys know).  The pedal is alone - no others in a chain.  Not my power supply either - a customer returned it to me for service, so the problem has happened in several locations and setups.  Here's a link to the layout:

It's early here, and the coffee hasn't yet soaked in, so I have't dug through that tagboard layout; with that as preamble, it is also possible that the sections of the hex inverter that are not used are not tied to an inactive state. If that is the case, they can be picking up >>anything<< from the circuit board or the air itself and causing noise at odd times.

The other guesses are good as well. It takes remarkably little leakage, pico-amps in some cases, to cause a CMOS inverter gate to flip states.

Also, don't give in to the idea that there is one and only one cause. They may be layered like onions.

[anotherjim]

Better 3PDT stomp switch wiring. This places ground for the LED between the jack contacts and reduces click due to capacitive coupling between switch contacts.

The Red Llama. The output cap is very generously sized at 10uF. It can be reduced to 1uF. Actually, for guitar, it can also be as small as 470nF allowing it to be a film type. I would fit 680nF film, since that goes all the way down to nearly 20Hz.

[digi2t]

Working off what R.G. said....

Looking at the vero layout, the loose pins on the 4049, some schematics show to be tied low, others show tied high.

I understand the premise behind tying the unused pins high or low, as long as they're tied, it should work fine. But, if an LED is at play here (not clear to me if it is), and / or maybe due to the board layout, tying them low might make it more stable? Seems to me that you've really covered all the other bases.

Of course, that will require some serious reworking of the layout.

[reddesert]

Better 3PDT stomp switch wiring. This places ground for the LED between the jack contacts and reduces click due to capacitive coupling between switch contacts.

This method doesn't ground the effect input when in bypass. That can be addressed by running a jumper from circuit input to the unused switch pad, ie from top left to bottom center.

I don't think it matters much for noise purposes whether you tie the unused inputs of a CMOS inverter high or low.

[anotherjim]

I'm not sure if it should be necessary to ground the input with the switch. I thought that was only needed to silence really high gain circuits that otherwise can bleed when bypass via stray coupling. It can't hurt though.

The output doesn't need an anti-pop resistor since the volume pot does that job.

[antonis]

I'm not sure if it should be necessary to ground the input with the switch. I thought that was only needed to silence really high gain circuits that otherwise can bleed when bypass via stray coupling. It can't hurt though.

The output doesn't need an anti-pop resistor since the volume pot does that job.

Both true Jim but in real(leaky) world sometimes grounding In & Out is unavoidable..
(even when both are grounded via some high value resistor..)

After all, you'll not have to worry about "break-before-make" or vice-versa switching.. 

[Bishop Vogue]

After switching out almost every single component and following several false leads, I finally fixed the problem by inserting a 220nf cap between lug 2 of the Vol pot and lug 3 of the stomp switch.  I don't know why it works, but it works.  Just thought I'd post this solution in case anyone else has the same frustrating issue.  Maybe this fix will work for you, too.

[rankot]

What is connected to lug 3 of your stomp switch?