Best True Bypass Wiring?

[Khas Evets]

I've noticed two different wiring schems for the 3PDT pushbutton true bypass switch mentioned in the forum. What are the advantages/disadvantaged of the different approaches?

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[Sic]

the two pictures are different

one is a DPDT which has 6 lugs

and the other is a 3pdt or TPDT which has nine

[petemoore]

The first one shows input goes to ground during bypass use. This could reduce noise in some circuits during bypass.
 The second [which I can't see this time but did last...puter's actin' up again...keep getting action cancelled then desktop...]
 The second shows a 3PDT using the 'middle row, in this case to switch the LED on/off using only one throw of the 'center 1PDT'.
 I use the second method with the LED in the middle separating the input and output [more than a DPDT could] which is useful for bypassing high gain circuits to reduce noise-illations etc.
 Sometimes I put 2  pulldown resistor from ground [1M or bigger up to 4M7] right on the switch [about 2M2 to each circuit connection] to prevent popping when switching, and if I want to change the circuit, I don't have to resolder on the switch, I put the in/out right on the resistor leads.
 Mark your in/outs till you get used to it, I go {left/right = in/out } on my pedals jacks.

[R.G.]

... you could go read "The Technology of Bypasses" at GEO (http://www.geofex.com)...

[cd]

... you could go read "The Technology of Bypasses" at GEO (http://www.geofex.com)...

Dang!  You beat me to posting that link!!!

[Khas Evets]

Sorry I should have clarified that I'm interested in the input grounding difference between the two, not the LED. So imagine the top one has the extra middle row for the LED.

[R.G.]

Grounding the input (or anyplace in the effect circuit) makes for a much quieter setup if layout and wiring is bad. It keep parasitic capacitance from coupling signal into the effect and the out into the bypassed signal path where you can hear it. Some effects circuits go unstable when their inputs are open and wiring is poor, and they oscillate. Grounding something in the effect signal path prevents that too.

It's useful if you have problems with the circuit oscillating or coupling signal in and out. There are other ways to do both, and ways to make the Millenium Bypass circuit ground something in the effects circuit as well.

[vanhansen]

For what it's worth, I just wired up my Crybaby with True Bypass using a DPDT and it's wired like the first image.  It is super quiet switching it on and off.  Definitely an improvement over stock.

My other projects will use a 3PDT like in the second image.

[Khas Evets]

Thanks for the replies. I'm going to try the first one. It's any easy fix if I don't like it.