Quote Originally Posted by Stratmangler View Post
I didn't post the picture of the isolating transformer box as a cure to anything.
I was just showing a bigger, more complete version of the XLR model Ali posted.

The cure is, as you've already pointed out, tracing the loop and then breaking it.
I wasn't criticising the use of an isolation transformer, just pointing out that if mains hum has already got into the signal path, fitting a transformer downstream of the signal is not going to stop it.

If however the mains hum is due to an earth loop, and it is not possible or convenient to fit earth lift resistors, then a 1:1 transformer placed in the signal pathway is a neat way to break the loop. But in adding an extra component into the signal path, the quality of the isolation transformer is important in respect of both frequency and phase bandwidth.

I note the transformer unit is fitted with XLR connectors. I would have thought if using fully balanced interconnects between items having true dual-differential input/outputs, mains hum breakthrough would not be a problem.