Switching - Input Grounded vs Output Grounded vs in and out Grounded?

[carboncomp]

When it comes to true-bypass switching what are the pros and cons to Input Grounded vs Output Grounded vs in and out Grounded?

[Rob Strand]

You need to post schematics.  I can only guess what you means by those terms.

Anything that shorts the output to ground would be undesirable (except in special cases where it's OK).

Shorting inputs is generally OK.   It has less problems than leaving inputs open, especially on high gain pedals.

[idy]

Grounding input is common in pedals and mixers and things. Grounding output is not. Have you seen it somewhere? I routinely ground the input in bypass. Never seen that for output.

[GGBB]

Anything that shorts the output to ground would be undesirable

Rob - would you kindly enlighten me about this? What harm can this do (assuming no DC present)? I don't do it but I didn't think it was problematic.

[carboncomp]

You need to post schematics.  I can only guess what you means by those terms.

Sure thing!


[/quote]

[antonis]

I presume, but it's only a guess, Rob deals with an output cap directly grounded when by-passed with the rest of preceding circuit "active"..
(oscillation lurking,,)

[antonis]

@ carboncomp: Rob asked for particular circuit  - not the 3PDT switch wiring..

[GGBB]

For the record - I drew that as a wiring possibility/guide, not as a recommendation.

[GGBB]

I presume, but it's only a guess, Rob deals with an output cap directly grounded when by-passed with the rest of preceding circuit "active"..
(oscillation lurking,,)

But wouldn't any oscillation be due to a floating input rather than the grounded output (asking)?

[carboncomp]

@ carboncomp: Rob asked for particular circuit  - not the 3PDT switch wiring..

I mean technically that is a circuit 

Just looking for how to wire a generic 3PDT footswitch PCB, mainly for PNP fuzz as that's 90% of what I like playing around with.

[GGBB]

Just looking for how to wire a generic 3PDT footswitch, mainly for PNP fuzz as that's 90% of what I like playing around with.

[carboncomp]

Just looking for how to wire a generic 3PDT footswitch, mainly for PNP fuzz as that's 90% of what I like playing around with.

Thank you, sorry that should have read

Just looking for how to wire a generic 3PDT footswitch breakout PCB, mainly for PNP fuzz as that's 90% of what I like playing around with.

With that layout would I attach the spare lug to the GND plane?

[GGBB]

With that layout would I attach the spare lug to the GND plane?

No - the spare lug is only grounded when "in bypass mode". The "Gnd" lug would be used for the ground - connect it to the PCB or possibly to some other common grounding point such as the input jack sleeve. For example:

[antonis]

But wouldn't any oscillation be due to a floating input rather than the grounded output (asking)?

There is always the possibility, especially for multi-stage circuits, of extrinsic interference and/or intrinsic crosstalk..
(even just a noisy circuit could result into a blown out capacitively grounded output..)

P.S.
I always wire my builds' switches for In AND Out grounded when bypassed (regardless pull-down IN-OUT resistors/pots existence) with no issue but it ain't necessarily correct..

[Rob Strand]

Rob - would you kindly enlighten me about this? What harm can this do (assuming no DC present)? I don't do it but I didn't think it was problematic.

I presume, but it's only a guess, Rob deals with an output cap directly grounded when by-passed with the rest of preceding circuit "active".. (oscillation lurking,,)

But wouldn't any oscillation be due to a floating input rather than the grounded output (asking)?

Antonis got the main point.  If you grounded the output *instead of* the input then the circuit could be misbehaving and putting junk on the power rail or coupling capacitively coupling that junk into the selected audio part.   If that does happen then shorting the output would only cause the output shorted to make matters worse because of the extra currents flowing.   Sure there will be plenty of circuits where none of that will happens with the output shorted but they aren't the extremes we want to protect against.

If the input was shorted then none of that bad behaviour will occur, since it usually a better condition than when the circuit is operating with an external input.   So input shorting is generally better.

You can short the outputs for power up muting.  In this case we know the outputs contain the thump.  We kind of assume the circuit is at least behaving as well as could be behind the scenes.  Also, the outputs generally have series resistance added to avoid overloads.

[antonis]

Cons: If the input is grounded, it can result in a pop or click sound when the effect is engaged or disengaged.

On the contrary..!!
(you may, and have to, consider input grounding via a veeeeeery small value resistor..)

P.S.
Welcome..

[amptramp]

If you have a delay-type circuit like a tape delay, grounding the input means there will be a gap in the signal output equal to the delay.  In this case, it is better to leave the input operating normally and not ground anything.

Grounding the output is going to cause problems.  Some designs have high current capability in the output stage like op amp outputs that might put out 20 mA.  Even if the DC path is isolated, loading the AC path through an electrolytic capacitor will cause the feedback to go from a stable configuration where you have a feedback resistor, preferably in parallel with a capacitor across it in normal operation to an output with an output capacitor connected to ground.  The output impedance of the op amp in conjunction with this capacitor will cause a feedback lag that can cause oscillation.

[duck_arse]

welcome? to a spammer? never!

[antonis]

welcome? to a spammer?

You SHOULD warn us..!!~!~

[duck_arse]

check the .sig line of any first-time poster, especially if the post is the kind of boring drivel you get from AI. they sometimes use reversed colour, sometimes 1pt text, sometimes a scroller thing.