Some questions about different ways to bypass...

[JJRockford]

1. If I want to add a buffer to a curcuit, should the buffer be added so the signal always pass through the buffer, or just when the signal _don't_ pass the main curcuit?

2. How do I do to add a led if I'm using DPTP-switches?

[Mark Hammer]

Opinions are divided about buffers and bypass, and about the use of mechanical switching vs electronic switching.  What causes this division of opinion is not rightness and wrongness but the "What about if....?" factor.

For instance, what about if your batteries or adapter suddenly crap out on you?  Buffers require power, true bypass doesn't.

What about if you have no idea whatsoever what the input impedance of the next device/stage in line will be or how long a cable you'll need to reach it?  Buffers prepare the signal for whatever else is out there.

What about if you have a dozen or so pedals in series?  Individual buffers don't produce much noise, but cascading a bunch of them (all in "bypass mode") adds up without contributing anything to sound quality, and maybe even detracting....unlike a straight wire feedthrough.

What about if you have a really hot signal?  Buffers are often used in conjunction with FET switching and FETs are not immune from distortion (although one would like to think that manufacturers select them well and integrate them into the design in a way that minimizes risk of undesirable distortion).

What about if you want to have a status indicator LED?  Conventional DPDT stompswitches, and most certainly SPDT switches (as used in the "classic" pedals) don't provide any means to switch the relevant leads AND provide status indication, whereas use of solid-state switching or use of a buffer a DPDT can.  Besides, 3PDT switches are costly and not as easily obtainable sometimes.  Use of a buffer to reduce the impact of having the remainder of the circuit connected when in "bypass" mode (à la Pete Cornish pedals) permits one to simply switch the output lines of the pedal (the way they did it in 1972 when we thought no one would ever have more than a pedal or two) and use the other set of contacts on a DPDT switch for switching LEDs.

There are more "What if..." concepts, but I have a meeting to get to so I'll stop here.  The point is that there is no real reason to use buffers or straight wire exclusively.  They each have their shining moments where they come through for you, so think about your own context, pedal complement, and needs.

[JJRockford]

"What about if you want to have a status indicator LED? Conventional DPDT stompswitches, and most certainly SPDT switches (as used in the "classic" pedals) don't provide any means to switch the relevant leads AND provide status indication, whereas use of solid-state switching or use of a buffer a DPDT can. Besides, 3PDT switches are costly and not as easily obtainable sometimes. Use of a buffer to reduce the impact of having the remainder of the circuit connected when in "bypass" mode (à la Pete Cornish pedals) permits one to simply switch the output lines of the pedal (the way they did it in 1972 when we thought no one would ever have more than a pedal or two) and use the other set of contacts on a DPDT switch for switching LEDs. "
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That was two very long sentences for my far from good english... Could you please explain it further?

Anyway, thanks for a lot of "worth of thinking"-stuff! If you can think of anything more, please write it!

One of the things you wrote seemed to be extra intresting: "What about if you have no idea whatsoever what the input impedance of the next device/stage in line will be or how long a cable you'll need to reach it? Buffers prepare the signal for whatever else is out there".

IF I know which effects I would like to connect before/after, are there any way to "match" them together? For exampel, if I know that my treble booster will be connected into my wha-wah and from there directly to my amp, are there any trix to match things like the resistors or something like that, to avoid the use of one or several buffers?

Sincerely,
Jonas

[R.G.]

Jonas,

Go read GEO. Start with "The Technology of Bypasses", work your way through all of the "Technology of..." series, and throw in the Guitar Effects FAQ. Then come back and ask about the pieces you didn't find.

It'll save us some time.