Noise from pedals in a patchbay when not in signal path

[Echos]

Leave the speaker connections as they are. There is nothing wrong with having more than one ground connection with properly designed gear.

OK. I hear you. I'll leave them be.

[Echos]

Just a note to say that I swapped out the Samson S-patch Plus for a Neutrik NYS-SPP L1 Patchbay which allowed me to gang the grounds. I added the adapters to create a ganged ground (every jack shares the same ground).

With that done I could:
- Remove the ground cable running from the rack chassis to a waterpipe
- Remove the Radial

I can now leave pedals plugged in and powered on, regardless of whether they are in the signal path without any noise.

Morals of the story:
- Check the every plug to make sure things you think are grounded actually are.
- You might have a ground-loop from your audio-interface to your computer, so may need to isolate your USB cable.
- If you're using isolated power supply and leaving a device plugged into a patchbay that isn't in the signal path, it doesn't have access to a ground unless the patchbay inputs have a shared ground (most patchbays seem to only have grounds shared between opposite jacks). Without access to ground you are probably going to experience noise unless you power off those devices.

[Echos]

Also, thanks everyone for your help. Much appreciated.

[Drew Stephenson]

Thanks for coming back and letting us know how you got on.

[Hugh Robjohns]

Excellent. I'm very pleased theory and practice have aligned to give you a noise free system.

Well done on your perseverance.

[digitalgeist]

Hey folks - it's my very first post here and I just wanted to say I have this exact same problem (line noise using pedals through a Samson S-Patch) and I'm methodically and patiently trying to solve. Going through this thread has helped me better understand what I'm doing wrong (and what I'm doing right) in my own setup and tips to address things I hadn't thought of. I have the Neutrik Patchbay on order as well.
Most importantly it's stressed to me to be thorough in testing things out. Echos, the OP, thanks for posting your journey with this as it's helped me on my own.

I'll add this too - USB noise really stinks. With so many gadgets/FX/synthesizers on the market that rely on USB for power and data transmission the chances of there being a noise problem with these are inevitable.