pedals are whining...but why?

[Kipper4]

The above diagram is a nice example of the input going to ground on bypass.

[Paul Marossy]

Some pedals whine when the inputs are open or connected to too high an impedance. The input is high impedance and if it's not pulled down by an input, you can get signal coupled in from the output wires capacitively. Connecting up a cable amounts to connecting up a capacitor across the input, which may load the feedback enough to stop it. Some pedals oscillate with a guitar connected, or with certain settings of the volume control, generally in the middle of the range.

It's generally a wiring capacitance issue.

So the "whining" then is the circuit oscillating because of there being nothing on the input? Wouldn't a small-ish cap to ground on the input prevent that from happening?

[Mark Hammer]

Whining pedals?

You just have to learn to say "No" to them more consistently, and not give in.  Otherwise they get spoiled.

"But Boss-ey got a new battery.  Why can't *I* have a new battery too?  Please, please, please, puh-LEEEEEEEEZZZZZ?"

[thelonious]

So the "whining" then is the circuit oscillating because of there being nothing on the input? Wouldn't a small-ish cap to ground on the input prevent that from happening?

I was wondering that, too. I seem to recall seeing a 47p to ground used like that in a couple schematics before. Or---are there such things as switched stereo jacks? Because that would just shunt the input to ground when the cable was unplugged, and could still switch the battery ground via the ring.

Whining pedals?

As the parent of a two-year-old... I would definitely send those pedals to their room.
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EDIT:
Stereo switched jack options - Switchcraft 14B are the metal version, but they are kind of expensive. Rean NYS212 are a less expensive, plastic "Cliff" type; you'd just have to make sure you ground the enclosure somehow if you use those. Smallbear has both - http://www.smallbearelec.com/servlet/Detail?no=1041 and http://www.smallbearelec.com/servlet/Detail?no=771

[Paul Marossy]

As the parent of a two-year-old... I would definitely send those pedals to their room.

I have a 9 & 11 year old and we still get whining on occasion. 

[duck_arse]

a mono-switched at the input and power switching with the stero output jack would work.

[thelonious]

I have a 9 & 11 year old and we still get whining on occasion. 

My wife might say that she has a 31-year-old and still gets quite a lot of whining...

[thelonious]

a mono-switched at the input and power switching with the stero output jack would work.

Good call! Then it wouldn't require any unusual parts.

[Paul Marossy]

I have a 9 & 11 year old and we still get whining on occasion. 

My wife might say that she has a 31-year-old and still gets quite a lot of whining...

Ha ha, I have some years on you and I whine myself sometimes. 
Human nature I guess? 

[alphadog808]

So last night I ended up removing the default 2.2M or 2M resistors from the board and put in a 120K resistor instead; it worked great/fine.  I wish I had waited a bit longer, it would have been easier and less painful on my fingertips if I had just swapped out input/output jacks  

Oh well, it was a great lesson to learn and if it happens again, I can try the jack solution!

Thanks again for all the help; hopefully the Wampler Pinnacle build will go smoother...*gulp*!

[R.G.]

The issue is that the pedal input is very, very sensitive to any signals coupled in, and even microscopic capacitances between wires can make enough feedback to cause it to squeal.

Putting almost anything across the inputs can cause so much loading that the tiny capacitance can no longer get a signal big enough to cause squealing into the input with the loading.

A resistor across the input is best, as it loads the feedback evenly across all frequencies (at audio, anyway). I mentioned the cord loading the input with capacitance for completeness, as there was a mention of the cord making the squealing quit. In some cases I have seen, the feedback issues were so bad that an input capacitor load would not stop the squealing, just shift its frequency a bit.

A pull-down resistor is the best choice, as long as the resistance needed to stop the squealing is not so low that it also wipes treble off your guitar's signal, which it can also do. This is still a band-aid.

The real solution is to fix the wiring layout and other signal routing issues on the board and wiring to controls so the capacitances that cause the squealing are smaller and don't give enough feedback to cause the squealing in the first place.

[Paul Marossy]

The issue is that the pedal input is very, very sensitive to any signals coupled in, and even microscopic capacitances between wires can make enough feedback to cause it to squeal.

Putting almost anything across the inputs can cause so much loading that the tiny capacitance can no longer get a signal big enough to cause squealing into the input with the loading.

A resistor across the input is best, as it loads the feedback evenly across all frequencies (at audio, anyway). I mentioned the cord loading the input with capacitance for completeness, as there was a mention of the cord making the squealing quit. In some cases I have seen, the feedback issues were so bad that an input capacitor load would not stop the squealing, just shift its frequency a bit.

A pull-down resistor is the best choice, as long as the resistance needed to stop the squealing is not so low that it also wipes treble off your guitar's signal, which it can also do. This is still a band-aid.

The real solution is to fix the wiring layout and other signal routing issues on the board and wiring to controls so the capacitances that cause the squealing are smaller and don't give enough feedback to cause the squealing in the first place.

Good information to stick in the mental Rolodex.