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SierraLima

Stereo 1/4" TRS Cable Channel Intefering With One Another

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Hey Gents,
   So I've been working on a project for about a month where you can switch between neck and bridge pickups via either a footswitch on a pedal or via MIDI messages from an effects processor as opposed to a standard pickup selector switch on the guitar. The idea is eventually I'd rewire the guitar with a stereo jack with 3 conductors: neck pickup signal, bridge pickup signal and ground/shield. This would be sent via a 1/4" TRS stereo cable.. See below if you want more details:

Anyhow I've got the entire Teensy Arduino programmed and the pedal running successfully on a breadboard. That's at least as far as my multimeter and connectivity tester is concerned. In real life I'm having a problem where the signal from the neck pickup is coming out (not at full blast but is quite audible) on the bridge pickup conductor and vice versa. I'm using this 15 foot stereo cable off of Amazon:
https://www.amazon.com/CableCreation-6-35mm-Balanced-Stereo-Meters/dp/B01JY2CV1U
Is it possible that the somewhat long cable is acting as an antenna where say the neck pickup signal conductor is transmitting magnetically and the bridge pickup conductor is receiving it? That's my suspicion which I think is theoretically true but I didn't expect the problem to be anywhere near this pronounced. If so any thoughts on how to eliminate this or at least minimize it to an inaudible level? Is this just an artifact of using a cheap cable with perhaps inadequate shielding?

Thanks,
   Omri

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I'd be more looking into the possibility that your output jack on the guitar is miswired, or there's a wiring error on the input at your switching device.

Cross-bleeding of the two pickups over the cable is possible, but unlikely to be audible to the point of standing out as a problem.

 

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On 3/10/2020 at 4:01 AM, curtisa said:

Cross-bleeding of the two pickups over the cable is possible

cross channel talk jumped out at me too.

it may have to do with the TPS cable...

balanced vs unbalance, and load impedance  (hi vs low impedance circuit design).

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Hey Guys,

   So I sorted out the problem. Lack of grounding for the signal of the inactive pickup. I'm using a DS2Y-S-DC5V DPDT relay for switching pickup signal. Before I was using just half of it and as a SPDT connecting the active pickup's signal to the final signal. The inactive pickup's signal was just an open circuit and not connected to anything. I'm now using the full double pole of the DPDT relay and the inactive pickup's signal is shorted straight to ground/shield. Works now.

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