Benefit to lifting the ground in XLR

[John B]

Quick question,

I'm using a DI box from Radial (AV2) to connect an unbalanced line level to an XLR mic input. There is an option to lift the ground on the XLR cable to reduce potential ground loop issues. I have no noticeable loop issue. Would it make sense to lift the ground for any other reason aside from isolating a loop in this configuration, or should I avoid lifting it unless there is a problem?

 

[NiagaraPete]

avoid lifting it unless there is a problem

Yes

 

[Speedskater]

With well designed components, not ones with the 'Pin #1 Problem' and powered from the same AC circuit there should be no advantage to lifting the shield (there is no 'ground' wire in a balanced interconnect system).
In a large TV or movie studio with more than one AC power source they sometimes need to lift the shield at the receive end ( but that hurts the high frequency interference problem) (so the use a hybrid connection at the receive end).

 

[fpitas]

In a large TV or movie studio with more than one AC power source they sometimes need to lift the shield at the receive end ( but that hurts the high frequency interference problem) (so the use a hybrid connection at the receive end).

I've seen people insert a 1kV 0.1uF ceramic disk in the shield lead.

 

[Speedskater]

The other pro audio problem with lifting the shield is:
Phantom power microphones won't work!
So if on location they run the wrong cable they have a real problem.

 

[John B]

Thanks all,

I snipped some of the spectrogram from both configs and put them side by side. Left of the marker is grounded directly from source to mic input, right is with ground lifted at the AV2 DI box. Oddly, very slight increase in ground noise with the lift, though at these levels nothing to write home about. (This is after RIAA curve correction, btw)

 

[LTig]

I use a Behringer DI box for a connection of PCs (Notebooks) to a professional PA system. The power mixer and the notebook power supply do not use the same outlet. Several times I had to use the ground lift to get rid of hum and noise, but not always. And I only use it when necessary.

 

[Speedskater]

A microphone or any battery powered unit needs to have the shield connected at both ends.