# My buffered bypass pedals are producing squealing under certain conditions.



## marksescon (Mar 10, 2021)

Very weird issue that I am having. 
Example Video: 



I incidentally discovered this while doing QA on my pedals - I get squealing when the following conditions occur:
(1) Cord plugged in between amp and pedal. 

(2) Pedal is powered but effect not engaged. 

(3) No cord plugged into input jack. 


I first discovered it in one of my Klones (Kliche), but upon investigating my other buffered bypass pedals (like the DRV/Informant), the squealing is present under the same conditions. Squealing changes frequency when adjusting gain and tone knobs. 

When a guitar is plugged in, there is no more squeal. Furthermore, the effects work perfectly fine. No squealing or weird buzzing other than what you’d find in any high gain circuit. 

Things I’ve tried that *have not* worked: Audio probe (difficult to do too because I need input audio jack to be open); different audio jacks like Lumberg, Open Frame, Enclosed; different amps and cables and even power supplies (I have Truetone CS12, 9v batteries with 2.1mm adaptor, and even a regular 9v dc jack); different ICs (I have stock from Tayda and Mouser); checked for any grounding issues (nada); and finally, checked soldering and joints. 



The only way I have found to remedy the situation is to actually make the pedal true bypass, which is why I am sort of concluding it’s a buffered bypass issue. However, I don’t want to draw any conclusions without soliciting the insight of the community. 



I know common courtesy would dictate that I post pictures of every pedal; however, because this seems to be a widespread issue and not isolated to one pedal, I felt the video example would serve as a foundation to your answers.


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## zgrav (Mar 10, 2021)

This could be normal behavior.  I will get noise from the amp when I unplug my guitar from the pedal chain and everything is still on.  A buffered bypass is an active circuit. when there is no input from a grounding signal line the circuit is still amplifying whatever stray sounds it can find.  We might even see folks starting to use these "spirit input" boxes on the ghost hunting reality shows....


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## marksescon (Mar 10, 2021)

zgrav said:


> This could be normal behavior.  I will get noise from the amp when I unplug my guitar from the pedal chain and everything is still on.  A buffered bypass is an active circuit. when there is no input from a grounding signal line the circuit is still amplifying whatever stray sounds it can find.  We might even see folks starting to use these "spirit input" boxes on the ghost hunting reality shows....


I think you are probably right. Truth is the only way to replicate my issue is to set up the pedal in a manner that most people would not (plugged in only to amp, powered, dimed, then start twisting knobs at random with no guitar plugged in). Especially since the circuit itself has no other issues.


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## PJS (Mar 11, 2021)

The other thing is that it might be something weird with the input circuitry on your amp.  Have you tried the same test with a different amp?  Also, what about different leads?


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## giovanni (Mar 11, 2021)

I was also wondering if you tried a different power supply, different room, maybe other pedals in the chain? It may very well be that the pedal is picking up some radio signal or some noise from the power supply. Trying different scenarios will narrow it down. Good luck!


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## giovanni (Mar 11, 2021)

Actually from the clip it kinda sounds like the buffer is self oscillating? Like it sounds like a fuzz factory with stability to a low value where you can literally control the self oscillation frequency with the gain knob. Which buffer?


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## marksescon (Mar 11, 2021)

giovanni said:


> Actually from the clip it kinda sounds like the buffer is self oscillating? Like it sounds like a fuzz factory with stability to a low value where you can literally control the self oscillation frequency with the gain knob. Which buffer?


Kliche (Klone) and DRV (Informant).

I have not built any other buffered pedals bedsides those two.


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## marksescon (Mar 11, 2021)

giovanni said:


> I was also wondering if you tried a different power supply, different room, maybe other pedals in the chain? It may very well be that the pedal is picking up some radio signal or some noise from the power supply. Trying different scenarios will narrow it down. Good luck!


 Yes different power supply and different rooms and different amps.


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## marksescon (Mar 11, 2021)

PJS said:


> The other thing is that it might be something weird with the input circuitry on your amp.  Have you tried the same test with a different amp?  Also, what about different leads?


I have tried different cables, amps, outlets, rooms. (It’s the only pedal in my path.)


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## marksescon (Mar 11, 2021)

Weird thing that happened: When I “held” the wire for the input jack (between jack and board, because on these buffered pedals the tip for the input jack goes straight to the actual board), the sound went away.


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## PJS (Mar 11, 2021)

So you are getting noise through the system with a cable plugged in to the input and nothing plugged into that cable?  Normal.  And yes, when you ground the signal line the noise will go away.  That is actually a quick and dirty way to check that signal is getting through.  Tap the end of the cable a few times and you will hear the taps.


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## giovanni (Mar 11, 2021)

That’s probably because you shorted the input? I’m wondering whether the buffer oscillates when the input is open. One solution could be a switched jack that shorts the input to ground when disconnected.


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## marksescon (Mar 11, 2021)

PJS said:


> So you are getting noise through the system with a cable plugged in to the input and nothing plugged into that cable?  Normal.  And yes, when you ground the signal line the noise will go away.  That is actually a quick and dirty way to check that signal is getting through.  Tap the end of the cable a few times and you will hear the taps.


Pedal with power. No engaged/activated. There is a cable from output of pedal to amp. Nothing is plugged into input. Oscillation/feedback produced when twisting knobs, gain and tone on both Kliche and Informant builds that are buffered bypass.


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## marksescon (Mar 11, 2021)

giovanni said:


> That’s probably because you shorted the input? I’m wondering whether the buffer oscillates when the input is open. One solution could be a switched jack that shorts the input to ground when disconnected.


With a stereo jack, how would I wire that up?

I also have these jacks which have a tip switch.


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## marksescon (Mar 11, 2021)

Okay so I discovered a solution thanks in large part to giovanni and Reddit. I used these jacks. It’s wired with a jumper so the input is grounded when nothing is plugged in. Thanks PedalPCB Community and Reddit!


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## giovanni (Mar 11, 2021)

I was about to reply, I’m glad you figured it out!


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