Ground loop hum
Ground loop hum
Submitted by usernaim on Mon, 2010-08-23 00:36I am running a G4 mini via HagUSB into the coax input of a DAC1. That goes into a Naim NAC 52 preamp.
If the Benchmark and my old CRT TV are connected to the pre, I get ground loop hum in those two inputs. The other inputs are clean. The hum goes away if the cable tv coax is disconnected from the TV. I've experimented with different cables, inputs, and to some extent, what gets plugged where (they are all plugged into one power strip which goes into one outlet).
Basically it comes down to this: cable tv plus Benchmark = hum.
Diagnosis? Solutions?
Thanks.
The sheilding on the TV-cable
The sheilding on the TV-cable coax is bringing a VERY different ground potential to your system. Everything else is grounded to the local outlet, but the TV-cable is grounded to the antennea outside.
You must break the ground on the TV-cable. The best way to do this is to use an isolation transformer. They are fairly cheap, and you can find them at Radio Shack, etc. But talk to your cable company and find out what specs you must look for.
Best,
Elias