Left/Right/Both Bypass switcher

[mth5044]

I've been putting thought into a stereo rig and one idea I've come up with is a stereo bypass switcher, but I'm having trouble getting my head around the bypass patterns needed to make it work.

The functionality would be like this: a bypass system for mono pedals that allows one to switch an effect on/off as well as switch it between left, right or both channels.

Guitar input would split. The output would be L and R. Those are the things I have down so far . Instead of tackling the entire thing at once,  I'd like to start with one loop. I envision it as two rails, one for the L and one for R. The input would tap into either the L rail, the R rail, or both. Now, switching between L and R wouldn't be too difficult passively, but the both option would require an active blend control. That would make putting temperamental fuzz circuits in the loops difficult, but I suppose AMZ's pickup sim could be used.

In any case, below is a mockup of what I'm thinking (using.. powerpoint?). Each triangle is a simple opamp buffer. There are two switches shown, the same color = the same switch. Currently shown, the effect is bypassed and you'd just get two clean L and R signals. If the green switch is thrown, the clean throw is lifted and the signal is routed through a buffer to the input, through the FX then to the output. Same thing happens if the red switch is thrown. If it was only one or the other, the input and output buffers wouldn't be necessary. When both switches are toggled, the inputs will be summed and the outputs will be split back to the L and R. So a TL072 for the input then TL074 and a handful of resistors for each 'loop'.

(Buffers are backwards on the out's  )


I can program a very simple uC for switching, the entry level PICAXE, so I'd probably do this with relays and momentary switches. I'm also a but curious about the interface... I suppose one stomp for on/off then a toggle to determine if it's L/R/both. Or three stomps for each loop.. L / R / Both.

Overthinking it? Underthinking it? I've been on it for about 10 minutes now so probably both. Any input is much appreciated.

[mth5044]

Hmm maybe it could be made easier by removing the input switch and only switch between the bypassed and the output of the pedal. The FX would always be getting signal through the buffers. This would allow for a common DPDT relay instead of an uncommon 3PDT relay.

[mself61]

are you still working on this or have you solve or found another solution ?, I am trying to do the same thing with 3 of my stereo multi effects units (modelers) , in the diagram your input signal will go mono into your FIRST stereo unit , so we have one input mono to a bypass switch that allows the signal to be output to the unit, I suppose the { Y } split could be an option, but the FX out has a R/L output to be sent back to the "RAIL" so there would be an R/L ( 2 lines) out of the FX, my current thinking is this - https://www.facebook.com/photo.php?fbid=10204331977112215&l=ab4fc2560c