Grounding Issue for DIY pedalboard

[tictac]

Hello there,

I built my 1st pedalboard using an aluminum frame and two diy modules made from cast Hammond project boxes.
Module 1 is a power module with an IEC plug + on/off switch. allows me to plug a power cable direct into the board.
Module 2 is a signal in-out patchbay which includes a mono guitar input/ pedalboard input and two outputs (mono/stereo)

Module 2 is my issue, I don't think I have it grounded correctly. The input jack is a metal switchcraft jack which provides a ground to the chassis and a ground point for a buss wire that grounds the 5 other I/O jacks which are the plastic Marshall type. My board is quiet as long as I don't use Module number 2. I get constant hum as soon as I plug in. I'm thinking it's because I've got the grounding scheme bass-acwards. Why am I using the guitar as a ground source? I'm thinking I should use the AC ground from Module 1 as a ground source for module 2. Why am I posting the answer to my own question? Not sure, haven't been on the site for a few years! I guess I was hoping to find a pretty drawing of correct pedalboard wiring

Thanks for reading...

[mauman]

Welcome back! How about a sketch of your current patch bay wiring/grounding scheme? What's connected to the outputs? How are you getting stereo out?

[phatt]

If you are going to run mains to a metal case (your module one I presume)
Then For safety reasons alone you definitely need to tie the mains earth to that metal case otherwise it could be deadly if something goes wrong.

As *mauman* already noted, post a layout or picture of the setup as there maybe other issues at play.
I use a mains powered pedal board and I tied the mains Earth to the common of the pedal supply as well. That setup has been working noise free for years now.

You can run into issues with ground loops in some situations and if that is an issue then you can simply add a ground lift switch to lift the pedal supply Common (Neg) from the mains Earth, **Do not ground lift the Metal case from mains Earth.**
Phil.

[tictac]

I found the culprit!

I'm using an EMI filter similar to the one above (mine has an on/off switch too) mounted in a cast aluminum Hammond chassis screwed to the pedal board frame.

Here's the way I have things setup: 1) guitar > patchbay-in > patchbay-out > amp 2) power module with EMI filter connected to 120 VAC = HUM

When I unscrew the power module chassis from the pedal board so there is no physical contact between the module and chassis = NO HUM

When you measure across line & neutral of these filters there is a resistance present, a very high resistance but a resistance none the less. I think what's happening is this resistance is providing a small load across the AC line which is causing the hum. Both modules, power and patchbay are screwed to the chassis. I'll need to: 1) isolate one of the chassis from the pedalboard or 2) make another power module without the EMI filter.

I'm thinking option 2 may be the better route to go....

tictac

[plush]

Nah, it's not an emi filter fault, but just a ground loop.
We still need a diagram though.

[tictac]

Still troubleshooting but I did find out that one source of noise is the Voodoo Lab Pedal Power x4 power supply. So I've ordered a CIOKS power supply to replace it.

I've attached a diagram of the pedalboard wiring so you can see what I'm up to.

[phatt]

Have you tried this yet?

Common (neg of your 9V pedal PSU) goes to the MAINS EARTH terminal.
Do not rely on alloy case for ground return.
Phil

[tictac]

Thanks for the tip! Regarding the grounding issue, the Voodoo Lab power supply I was using had no ground reference since it was using an external power supply L & N only (like your drawing shows) The CIOKS power supply I'm using now has a 3 prong IEC plug and a metal chassis so the AC goes straight into the power supply itself. I'm not having any more noise issues.... dave