Buffered bypass with SPST momentary switch.

[egasimus]

It kind of sucks that there isn't a good way to browse all the knowledge accumulated in this forum. I really should compile some info for the wiki when I have some time - it's quite underpopulated and underused.
Anyway, I know you've been asked about this a good hundred of times, but what's a good buffered bypass for a momentary SPST button? I have 2N5457 and BF245 JFETs, as well as BS170 MOSFETS - and I can also buy 405x and 4066 chips. Which way do I go? The circuit I'm building is a MXR Dynacomp, so I guess I'm gonna have to add external input and output buffers?

[R.G.]

True bypass solves a problem that was a big deal back in the 60s - how to keep a pedal from loading down a guitar signal when it's in bypass. Now that we have almost a half century of better technology under our collective belts, it's not nearly the issue it was. True bypass also prevents issues with dead batteries. How many people still use batteries?

If you have a good, high impedance buffer input, the effect is not going to load down the guitar signal even if it's not switched away from the signal in bypass. Hence the buffered bypass and the Clinton bypass work fine for preventing loading.  See "The Technology of Bypasses" at geofex for these descriptions. A very large amount of the collective wisdom is distilled at geofex.

A good buffered bypass? Anything with an input impedance well over 1M. JFETs and MOSFETs both qualify, as do JFET and MOSFET input opamps if the biasing and coupling arrangements don't cripple them.

For buffered bypass, you very seldom need a buffered output. The buffered input takes care of most of it.

[egasimus]

I see, thanks!
So do you think that using one half of a dual opamp as an input buffer and the other as a bistable multivibrator (see pic below) would harm performance in any way? E.g. popping, or maybe just some slow degradation in the audio part?
What's the smallest-footprint edge-triggered flip-flop in existence?



And, if I use something like this, with a 4053, do I still need to buffer the signal in front?