hi there, looking for advice, on my issue. Integra dtr-7. vintage now, but contiues to kick. on any 5.1 selection, ( multi-channel analog/DD/DTS/ or just 5 channel stereo, I sometimes get a noise just in the center channel, like a hum and hissing, low but breaks up audio from that channel when it does it. I have attempted to locate a scource, (electrical?) unplugged different appliances, any flouresent lights, it's not wi fi, and changed the surge protector, it has emi filter. And to make it worse, it will not do it sometimes. When it is clean, I get at full vol. just about 0 noise, when it acts up I get a hum a full vol. I did have luck stopping it by maxng the vol. (nothing on) , and once pulled the plug and let it sit a few and it stopped. Problem is if I send it for a fix I'm not sure it will act up.??? any thoughts? emi? electrical?