Hi Matt,
I'm sorry to hear that you are still having issues with hum in your system. Just for the record, the Axiom DSP has a three prong plug only for the safety earth connection to the metal chassis as it is not double insulated and hence a safety (and legal) requirement. The signal ground is floating relative to the safety (AC) earth, so it cannot be creating a ground loop in the typical sense. I don't want to question Anthem's design, but I find it very strange that they do not use a three-prong power connector. The reason I find this strange is that high power amplifiers almost always have a safety ground connection. From the photos I can find of the back of the MCA5, it does have CSA electrical approval, but it does not have a double-box double insulated logo on it anywhere. I don't know how this would have passed CSA approval without either having a safety earth connection OR being double insulated. I also find it very strange that they specifically recommend using the XLR inputs over the RCA inputs. Any amplifier that offers both should perform equally well with either input that is offered. None of that is going to help you with your problem, so before you jump to put anything up for sale, there are some simple things that should be tried:
Disconnect all inputs to the AV7005, but leave the DSP and your two power amps in the equation. Hum?
If yes, disconnect the outputs from the AV7005 to your AudioSource amp. Hum?
If yes, remove the DSP and connect FIVE pre-outs from the AV7005 to your MCA5 (maybe use the surround L/R to connect to the LFR rear sections for this test. Hum?
If yes, the MCA5 is the issue. If no, try connecting FIVE RCA pre-outs from the AV7005 (disconnect the XLRs). Hum? If yes, the MCA5 is the issue.
If you do get hum with either of these configurations with no inputs connected to the AV7005 and the DSP out of the loop, try connecting a wire from the ground screw on the back of the MCA5 to the phono ground on the AV7005. See if that changes the hum level at all.
Thanks,
Andrew
