February 5, 2006

Emotiva Hum Fixed

I mentioned earlier that I was having some difficulty with hum between the Emotiva DMC-1 and MPS-1. I tried all the usual ground loop hum tests and solutions I could think of, as well as trying individual channels over balanced XLR. None of this worked, until I tried something a bit more drastic.

I removed all of the unbalanced RCA interconnects between the DMC-1 and MPS-1. Then used a single XLR cable to connect only one channel between the two. And there was no hum. So I went and bought a Hosa XLR-803 snake. Using balanced XLR for all the channels has greatly reduced the hum, although it is not completely gone.

Swapping amp modules, interconnects, channels, and speakers didn't solve the hum problem. In fact, the hum seems to be a result of interference between amplifier modules, mostly in amp banks 5, 6, and 7, that goes away for a single channel if there is no RCA input to that module, and decreases for a single channel if the neighboring module has its RCA connection removed.

Moving to a fully balanced audio path has solved the problem, although the hum is still there. The DMC-1 and MPS-1 support a fully balanced path, according to the manuals, as the balanced and unbalanced stages are kept separate.

Posted by josuah at February 5, 2006 11:11 PM UTC+00:00

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