Single Device - Ground Loop hum

[philpoole]

I've been fiddling with my amp recently to reduce hum, and found that one of the contributing factors to my earthing problems was the preamp, so it's good to try and rule it out.

[redjr]

Originally Posted by philpoole

I've been fiddling with my amp recently to reduce hum, and found that one of the contributing factors to my earthing problems was the preamp, so it's good to try and rule it out.

its my new little preamp that was creating some hum - that I at least reduced. Further testing as I described above seemed to indicate otherwise. At this point I'm not sure where its entering the audio chain.

[redjr]

Update....

After more 'process of elimination' testing I discovered that the hum I was getting was indeed coming from my new amp build. I had tried hooking up some shielded cable from the RCA inputs to the amp module, but decided not to ground the shield. The decision not to use the shield (2nd wire) was based on some other discussions I had read here about star grounding strategy. For some reason it did not work for me.

To fix the problem I decided to use - readily available - 2 twisted pairs from some CAT5 cable I had. This was a departure for me from using RG-174/U coaxial cable. Connecting up both wires, at both ends, signal and ground has virtually eliminated the remaining hum. While there was some hum issues with my source selector device(since fixed), it was further amplified in my amp. Problem solved. It's now time to get the amp off the bench and into service.