Mysterious Buzz

[bassist_lewis]

I've had a read around the internet and can't find this exact scenario, so putting it to you guys.

I'm getting a bit of buzz when I from my setup, which is as follows:

 

Bass (single coils) > pedalboard > amp.

 

When I roll the volume down the buzz disappears, which implies it's something going on with the pickups/wiring. HOWEVER, when I plug straight into the amp... silence. So it's the pedalboard, right? Well, I have a GigRig power supply, so fully isolated, all pedals correctly powered and every pedal is in its own isolated loop using a GigRig QMX. I even have a noise filter (!) I currently don't have a buffer first thing as my Canvas Tuner is away getting repaired (fairly sure the buzz was there before).

 

Hoping someone out there knows electronics better than the internet.

[bassist_lewis]

Additional info:

 

- I use a Y-splitter to power the Generator and a Noble DI. I've tried powering them separately and the buzz is still there

- tried going straight from the switcher to the amp (i.e. cutting out the Noble). Buzz still there.