I think my 4520 is near the end of its life. It's less than 2 years. It sometimes, says headphone is plugged in, then become no sound, sometimes, it says calibration microphone is plugged in and menu pops up with no sound as well. But I have nothing plug in. Very annoying. I did compressed air trick, doesn't help. Only thing can temporary resolve the problem is by beating hard on the front or top, or even lift it like 1 inch and drop it hard on table, then it will recovery for 2 days...some connector inside or even some soldering joints are bad I guess.
Any way, quite disappointed with it's build quality, considering buying Marantz 7009 as replacement. It's almost at same price, but likely a down grade? What else to look at? Any suggestion? I like 4520 sound though, so I hope the next AVR is at least equal sounding or a bit better.