Troubleshooting hum and weird microphonics

[DesmoBob]

I made a custom pedal board. I have a 1/4" input jack for the guitar on the right side. The jack is connected via patch cable to the first pedal in the chain.

If I plug my guitar directly into the first pedal in the chain (i.e., bypass the jack on the side), all is well.

However, whenever I use the jack, the patch cable goes loudly microphonic, as do all the other patch cables between the pedals. There is also a loud hum. Do I need to put a filter on the jack? Is the jack itself functioning as some kind of bad buffer? Or is this a symptom of some other problem?

Originally, I had the input jack, plus a wireless receiver. Using a DPDT rocker switch, I could choose which signal (jack or receiver) I could feed into the first pedal. However, any time I switched to the jack input, I got the loud cable microphonics and hum. For now, to make it simple, I completely removed the switch & receiver from the circuit. The point I'm at now is just trying to get the jack to play nicely, period.

[Systematic Chaos]

I guess the jack is the problem/issue....some grounding or other probably.
For your application I highly recommend these:
http://www.neutrik.com/en/audio/plugs-and-jacks/locking-1/4-chassis-jacks/nj3fp6p-bag

[rnolan]

I'm with SC here, that jack seems to have issues, replace it, make sure you have good "shielded" connection to the first pedal (or just plug straight into the first pedal (for now  >:D )

[DesmoBob]

Thanks, I'll give that a try. I was able to source the NJ3PF6C, but not the NJ3PF6P (metal housing as opposed to plastic housing). Do you think it would matter?

(Currently I'm using a switchcraft jack.)

[Systematic Chaos]

The metal one will do just fine..I personally prefer the plastic housing ones for pedalboard/patchbay/rack installation though....

[rnolan]

Hey SC, do the plastic ones earth to the case ? if not (which is what I suspect) it reduces the possibility of ground loop isses and so would definitely be better, but depends on how you are setting up your pedal board ground plane (there maybe some scenarios where you want everything to earth to the case ?).