Hi Forum, I recently took delivery of a Cyrus DVD7 and the AV5. The two are connected with both a digital co-ax (for the DD and DTS decoding in the AV5) and a stereo input (to leverage the DVD7 CD qualities). Amplification is such: I have a Power driving the fronts, and an XPA driving the rears. I do not have a center channel amp, nor do I have a subwoofer, but both are on the way in the future. The AV5 is compensating for them being absent by mixing in the low frequencies to all speakers and the center channel into the fronts. The problem is that with DD material only I hear an annoying hum (sounds like a bee....though slightly higher in frequency), directly proportional to the volume and most pronounced on the rear speakers though still audible through the fronts. If I turn the rear amp off it's still audible through the front....though faintly. I suspect it's a ground loop somewhere and am wondering if anyone has some ideas? I might try using the optical inputs...that seems like the most logical next step, though after that I'm a bit stuck for ideas. Interestingly: - I definately hear it in DD mode. - I definately do not hear it in DTS mode. - I can't remember what happens in stereo mode.....but I think the hum is absent....I will try it again tonight. Lastly, I played a DTS track last night (Gladiator R1...no problems with the region, and it even outputs to a PAL TV in the correct format...nice) and the AV5 wouldn't mix the missing centre channel into the front speakers with the DTS audio, is that normal for DTS decoders? Incidently, picture quality is excellent, DD and DTS sound is impressive (DTS is a bit better though that's material dependant)and I have yet to notice any appreciable differences between the PCM stereo decoders on the DVD7 and the AV5 when spinning CD's. Both, however, are a step up over the old DAD1 that I have in the rack. Cheers, Andrew PS I double posted to the Amp section because I wasn't sure which section this query belonged to.