I was hoping someone could have a look at my wiring to make sure it looks reasonable from a grounding point of view. I recently built a few pedals and they all exhibit a slight hum when bypassed. The hum goes away if I touch the foot switch (the external toggle) with my hand. I tested that I have continuity between the following (I'm assuming that this is expected from what I've read here): enclosure (probed on the inside around the foot switch where there's less powder coat), I/O jacks (the washer on the outside as well as the ground points on the inside of the case), foot switch toggle on the outside, shield around the wire where applicable. I attached a couple of the builds, one with a shielded wire on the input and one without.
Potential Grounding Issues
- Thread starter punchy712
- Start date
Erik S
Well-known member
That looks like a pretty heavy powder coat. I think ideally your in/out jacks, pots, and foot switch would all have nice tight connections to bare metal.
I’ve seen some builders do some sanding at the contact points when they get an enclosure with a lot of paint or powder inside.
I think I’d start with the jacks and see if that makes a difference.
I’ve seen some builders do some sanding at the contact points when they get an enclosure with a lot of paint or powder inside.
I think I’d start with the jacks and see if that makes a difference.
jimilee
Well-known member
What Erik S said, start with the jacks then look at your power supply. Some circuits are more sensitive than others.
As an aside, you don’t have to use a stereo jack input if you’re not going to use a battery snap. The third lug is there to ground the battery when in use.
As an aside, you don’t have to use a stereo jack input if you’re not going to use a battery snap. The third lug is there to ground the battery when in use.
I was thinking about this too, but I thought that since I was getting connectivity between all the necessary parts then it's not really an issue. Is the problem that I may not be getting "enough" connectivity due to the powder coat? Also, would it be sufficient to sand the inside of the case and the inside of each hole, or should I sand a bit on the top of the enclosure too, where washers would go?
@jimilee those were just the jacks I had on hand and for whatever reason I like to give myself the option of adding a battery in the future, even if honestly that will never happen. In the future I'll start using mono jacks only and use the smaller 2 pin DC jacks, and that way I don't have to enlarge the drill holes to make this big one fit.
Thanks @Erik S
I wanted to add one more thing that I just figured out now. The issue seems to happen only when I plug a guitar in. If I touch the guitar strings or foot switch the hum goes away. I tried a few guitars and they all behave the same way. I connected the pedal to my audio interface and no issues at all there. Could the enclosure grounding still be an issue here, or is there something else not right (or is this expected)?
I wanted to add one more thing that I just figured out now. The issue seems to happen only when I plug a guitar in. If I touch the guitar strings or foot switch the hum goes away. I tried a few guitars and they all behave the same way. I connected the pedal to my audio interface and no issues at all there. Could the enclosure grounding still be an issue here, or is there something else not right (or is this expected)?
Erik S
Well-known member
I feel like an ungrounded input jack could be related to that kind of problem, but I am very much not the guy you want for real engineering answers.
Side note - if you’re going to unscrew your jacks and attempt to sand/ scrape without pulling all the guts out (as I’d be tempted to do) make sure to cover your pots. The lube on those things is super sticky and will grab that metal/ paint dust if you let it get in there.
Side note - if you’re going to unscrew your jacks and attempt to sand/ scrape without pulling all the guts out (as I’d be tempted to do) make sure to cover your pots. The lube on those things is super sticky and will grab that metal/ paint dust if you let it get in there.
Thanks for the suggestion. As much of a pain as it is to remove the guts especially after getting everything nicely tightened down and lined up, I'm not going to be lazy and I'll remove it all before sanding anything down. I don't want to introduce any other problems while trying to fix something.
You're positively radiant!
Plug the guitar in, hold it to your body(hear the buzz/hum), then set it down on the stand and take a step away.
If it goes away when you go away, it's likely coming from you. This is more prevalent in single coils and stacked humbuckers. Our bodies are spitting out electrons like everything else.
You're grounding yourself when you touch the strings, footswitch, etc.
Saw this recently posted on madbean forum:
If this is the case, as far as solutions go, have to ground yourself and keep away from the depleted uranium.
Can also check the environment and see if you are acting as an antenna for something. Turn off wifi router, led and florescent lights, etc. Anything that's emmiting RFI.
Plug the guitar in, hold it to your body(hear the buzz/hum), then set it down on the stand and take a step away.
If it goes away when you go away, it's likely coming from you. This is more prevalent in single coils and stacked humbuckers. Our bodies are spitting out electrons like everything else.
You're grounding yourself when you touch the strings, footswitch, etc.
Saw this recently posted on madbean forum:
If this is the case, as far as solutions go, have to ground yourself and keep away from the depleted uranium.
Can also check the environment and see if you are acting as an antenna for something. Turn off wifi router, led and florescent lights, etc. Anything that's emmiting RFI.
jimilee
Well-known member
Funny story. I was driving myself nuts trying to a solve a similar problem, I tried everything. Turns out, my and my strat were facing my computer monitor trying to figure it all out. Turned around, and it was fine.
Thanks all for the comments and suggestions, I really appreciate it. It's possible that it is just me as my amp and pedals are in my office where I also have my computer/monitors/etc. so there's plenty of RFI to go around. I'll try to get the stuff moved out to at least sort out this particular issue.
What kind of pups are you running?
RFI is a strange and sneaky beast.
I work on MRIs and spent nearly 2 weeks chasing an image artifact(MRs are extremely sensitive to RFI, they operate in a farady cage/shielded room).
Turn out, someone ran an unshielded cat5 cable across the high voltage and rf transmit lines and hooked it to a peripheral device. Noise was leeching onto the ground and spreading across the system as a result.
RFI is a strange and sneaky beast.
I work on MRIs and spent nearly 2 weeks chasing an image artifact(MRs are extremely sensitive to RFI, they operate in a farady cage/shielded room).
Turn out, someone ran an unshielded cat5 cable across the high voltage and rf transmit lines and hooked it to a peripheral device. Noise was leeching onto the ground and spreading across the system as a result.
That's a pretty cool story with the MRI, thanks for sharing. A lot of basic things that I didn't really think about before I find that I'm having to learn more about.
I'm using mainly humbuckers (Seymour Duncan Distortion and Black Winter and some Gibson ones as well). I have another guitar with some single coils, but they all show similar issues. I have a really old guitar with an EMG 81 active which I should try to see how it behaves.
brightlight
Active member
What kind of guitar are you playing with? And are those 2 pedals fairly gainy?
I recently built a Thermionic (Friedman BE-OD) and it's the highest gain pedal I've ever built. It was super noisy with my Ibanez RG, but went away when I touched a pedal foot switch, strings, 1/4" plug, etc. I tried all kinds of the usual troubleshooting stuff for noisy signals only to discover that the ground wire running from the bridge claw of that guitar to the volume pot casing had come undone. All noise gone. Stupid me
I recently built a Thermionic (Friedman BE-OD) and it's the highest gain pedal I've ever built. It was super noisy with my Ibanez RG, but went away when I touched a pedal foot switch, strings, 1/4" plug, etc. I tried all kinds of the usual troubleshooting stuff for noisy signals only to discover that the ground wire running from the bridge claw of that guitar to the volume pot casing had come undone. All noise gone. Stupid me
seriously, just try turning off all electronics in the room, including modern light bulbs. RFI(and EMI) is rampant in our world today, moreso every day. Everything resonates with and exchanges electrons with those frequencies to some degree.
Even a simple desk lamp can scream. When bench testing a circuit, I have to turn off my drafting magnifying lamp that was my grandfather's or 20% of my signal is noise. Most LED bulbs emit a ton of RFI noise due to cheap construction of the rectifier stages.
Turn everything around you off, then turn one thing on at a time. If nothing else, for shits and giggles.
