3PDT Wiring Question

[Brad Hill]

Reposting a 3PDT wiring question that I shared with the "DIY Stompboxes" Facebook page: I've built a 2 loop switcher using a 3PDT switch with a second 3PDT that bypasses the two loops. I have noticed that the NON-selected loop tends to bleed a little signal onto the selected loop and I'm pretty sure that this is because the inputs are NOT grounded (I know this can be an issue but still don't fully understand given the concept of "true bypass") so my question is this: can I ground the inputs on the LED indicator poles of the 3PDT as shown by the dotted lines in my photo without issue or is a 4PDT switch a MUST in this scenario?

[kgull]

Whoops

[AntKnee]

I agrwe you should ground out the unused loop when its not activated. That looks like it would work. I would test it first with some alligator clips if you have some small ones.

The point of true bypass is to take the audio signal completely out of the effect until you activate it. Since you are using two switches, you have one that "true bypasses" the looper, and one that switches between loops when the looper is activated.

[Brad Hill]

Yes...my first 3PDT switch basically chooses or bypasses the "loop" section of the pedal and then the switch shown in my diagram chooses between Loop 1 and Loop 2.  Not having a 4PDT switch at the time, I chose NOT to ground the Loop inputs because, in my mind, doing so would put the 9V power from the LED indicators onto the signal path?  My assumption the wiser move is to replace the 3PDT with a 4PDT, no?

[m-Kresol]

I did pretty much the exact same thing some years ago and didn't ground the specific inputs on the second switch. I only had the input of the selected effect grounded via the master bypass switch.

I think that your scheme should work perfectly fine, though. Depending on what type of circuits you're using, wiring can be important too. Maybe try to move around some signal wires (in and out) and see if that makes a difference. If so, either find a position where it's ok, or use shielded wire. this is especially true for high gain circuits like distortion or fuzz.