james david low

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Flip-Flop Loop Switcher / Dual Pedal Switcher

I have a couple of DIY overdrive pedals that I never have on at the same time. So I wanted to house them as a dual overdrive and then add Flip-Flop switching so that to go from one pedal to the other, instead of having to turn one off and the other on, you just turn on the one you want, and it automatically turns the other off. Could be used for a true bypass looper as well to switch pedals in the same manner externally.

So far I’ve done this with counter ICs. I planned to try and do it with a single dual J-K Flip-Flop with asynchronous reset, but I couldn’t get the clock debounce to work with that. Eventually, I came up with a clock circuit that works with a dual counter chip:

Schematic using dual counter chip:

Schematic using 2 counters. This uses a different debounce circuit which I’ve found to work with that chip:

I also chanced upon a debounce circuit that worked, when all the other types I found on the internet didn’t work that well with this particular IC chip. I’ve drawn out just that portion incase it’s useful to anybody else struggling with a chip clock timings. Even though both the 9V and GND should be AC ground, I found it would only work if I decoupled to both the positive and negative of the power supply: