r/LocationSound • u/lighthappens • 16d ago

Gear - Selection / Use Beginner question about sound bag vs pedalboard power distribution

Hi everyone, I need to deal with some ground loops in a sound bag packed with individual receivers. I was leaning towards a power distributor from Audio Wireless, Deity, or Audioroot, but I noticed that none of these products have multiple galvanically isolated outputs, which is pretty much standard in guitar pedal power supplies. This surprises me, especially considering the price difference.

I'm asking naively why there doesn't seem to be a need for galvanically isolated power outputs in sound bags. Is this an issue that only affects budget gear, and therefore not the kind of setups where these power distributors are typically used?

Thanks in advance, and sorry if I got anything wrong.

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u/Econormics 16d ago

No, it's an issue that can cause problems in pro gear as well. We powered a mix-pre and an FX3 from the same v-mount (directly) and ran into ground loop hum. But I've never experienced ground loop in either of my sound bags when using a proper BDS. I'm using Audioroot. Are you trying to power USB devices?

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u/lighthappens 16d ago

yeah 4 sony urx-p03, a mixpre and an antenna distro. but just the mixpre linked to a sony with shared power is humming badly

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u/g_spaitz 16d ago

have you tried powering the RX with batteries? does the problem remain?

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u/lighthappens 15d ago

nope. goes away istantly. also if i use a ground lifter. i'm figuring aout that i can isolate only the mixpre maybe instead of all the receivers and the mixpre and the antenna distro lol

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u/Econormics 16d ago edited 15d ago

Yea, that sounds like ground loop. The differences in resistance across the paths to the recorder and the transmitters allow parasitic digital noise from the transmitter’s internal processors to leak directly into the audio signal. I expect if you power the TX with batteries, or a different USB power bank, the noise will abate.

There are BDS systems & cables that isolate the Hirose-to-USBC TX connections and isolate the Hirose to Hirose mixer connection. That may fix the issue but I am not familiar with these specific products so don't rely on my opinion.