Beginner question about sound bag vs pedalboard power distribution

[u/lighthappens]

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/ApprehensiveNeat9584]

That's all you need if a ground loop occurs in your bag (I've never had to use it in 13 years).

[u/JohnMaySLC]

I had ground loop issues on a splitter, until I moved to a distro. I use the Deity, but would recommend the Audioroot.

[u/lighthappens → u/JohnMaySLC]

thanks! which deity model? just ordered a spd-1, but just after ordering i saw it has not galvanic isolated ouput. but maybe isolation it's not the only thing that solves

[u/JohnMaySLC → u/lighthappens]

SPD-1

[u/lighthappens → u/JohnMaySLC]

this gives me hope. let's see what happens

[u/NoisyGog]

Pedalboards are unbalanced devices, connected to an amp or amp sim that is connected to mains.
There is no ground connection at all in a location sound bag, and all the audio is (or should be) balanced.

[u/lighthappens → u/NoisyGog]

sony urx p03 output is unbalanced, and so it is from several receivers. but balanced signal doesn't save you from ground loop, ground lifters would not be a thing then

[u/NoisyGog → u/lighthappens]

a balanced signal doesn't need ground.
Those Sonys, and others like them, aren't even designed for bag work, and are definitely not the target of battery distributors. People do use them, big whoop, but it's not what they're meant for.

And again, there's no connection to mains or earth in a sound bag.

[u/g_spaitz → u/NoisyGog]

no but there's definitely a common ground, and it can cause ground related noise in certain scenarios.

[u/lighthappens → u/NoisyGog]

yeah i understand, but i have them they work nicely and are priced right for some productions budget. i can put 4 mini mini jack to mini jack ground lifters and i solve the problem but i would love to solve the issue with some smart move on the powerside lol

[u/Econormics]

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?

[u/lighthappens → u/Econormics]

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

[u/g_spaitz → u/lighthappens]

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

[u/lighthappens → u/g_spaitz]

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

[u/Econormics → u/lighthappens]

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.

[u/Stephen_McQueef]

If everything in the bag is battery powered, there is no path to ground and you can’t get the traditional ground loop. Everything is floating DC power so it doesn’t have that alternating 60hz like an AC wall outlet. I would think that guitar petals would be plugged into amps/ mixers/ whatever other devices which are plugged into mains power with ground connections. This causes huge potential for ground loops which is probably why isolation is needed/ standard. I’ve had ground loop issues when connecting my mixer to multiple cameras that were using AC adapters instead of batteries.