Stereo True Bypass Wiring

[spfautz]

I've built a true bypass strip and am attempting to have the last loop accomodate my stereo pedals.  What I'd like is for my mono signal (coming from dirt/boost pedals) to enter the switch and go out in stereo.  In bypass mode the switch would just split the signal having the same signal go out to two amps.  When the switch is engaged the signal would be sent out mono to my reverb (which splits it to stereo) and delay pedals (still stereo) and return to two loop inputs (left and right) and then out (left and right) through the two outputs.  I've struggled to find a wireing diagram for this, so I drew up my own.  Will this work? The unmarked line (turquoise) is the ground and would be connected out to ground as well.

[nocentelli]

That will "work", but I think you might get mismatched levels between bypass and reverb+delay engaged. Your signal will be passively split in bypass, but I imagine the reverb has some degree of input buffering to drive the stereo outputs, so might be louder than bypass... This may not be an issue if you can set the overall (wet+dry) level of the reverb+delay to match it with bypass, but if you can't solve it this way you could try simple passive level controls (with a single dual-gang pot?) on the left+right returns OR maybe try a buffer in front of the mono input to the switch.

[spfautz]

So if there was a buffered splitter after the first input lug, but before the split, this would work?  Doing it this way don't I have no control of the signal strength matching still.  Couldn't I over compensate this way and have a bypass signal stronger than the wet signal?

[nocentelli]

A simple, single FET buffer might be enough to prevent problems, but if you needed a "bypass level control" to match levels you could use something like this (the level control could be a trimmer inside the pedal to set and forget) -

From Beavis audio:



or there's a thread of them here:

http://www.diystompboxes.com/smfforum/index.php?topic=94578.0

I think this is a situation where you're probably best to try it out as you've drawn it, and see if there's a problem. If there is, you have some options to try. A dual volume pot on the stereo loop returns is the simplest solution, but means you are permanently reducing the signal level going to the two amps (either with passive splitting in bypass, or reducing the output of the stereo loop when it's engaged). The buffer or buffer+booster option means raising the bypass output to match the stereo loop level, but also means permanently buffering the bypass signal, which you might consider to defeat the whole point of your true bypass strip...