I realise it's over six years since this thread was started and the T763 is no longer available, but I bought one (new) about three years ago. It had been sitting in its box in a shop for about five years for some reason and had never been used. During the first 12 months, I took it back for warranty service because it hummed through the main front channels (I was only using two speakers). The service technicians replaced the multi-channel audio board and another in/out board and the hum vanished. It took me 18 months (from purchase date) to buy enough speakers to be able to turn on the surround modes and when I did, I discovered hum on the rear channels too. After a while, it got worse and was affecting all channels, but only in surround modes. In stereo it was absent. I took the unit back again, about a month before the warranty expired, and got the runaround. The service agent claimed to be unable to hear any hum. He sent it to the distributor in Sydney and they also claimed not to be able to hear the hum. When it finally returned to me, the hum was still there. About six months has passed since that experience and I've been putting up with the hum all that time. About three months ago I replaced two 2-watt resistors and some larger diodes in the ISC board (impedance-sensing circuit) suspecting the resistors at least of having broken down due to heat. That didn't help. Then this weekend I had another go. I removed the multi-channel board and re-soldered all of the joints on it, corrected a dodgy-looking earth joint where multiple earthing wires were soldered to an RCA socket pin in such a manner that they were within fractions of a millimetre of shorting to the signal pin, and put the board back in. That didn't help. Then I took out the DSP board and found a joint that looked dry where a short earth wire connects two sections of the board to each other. I re-soldered that and a few other large solder connections, put the board back in and now the hum is GONE. To anyone with an intermittent or worsening hum problem in a T763 (and probably any other NAD receiver), I recommend they go over all of the earth wire connections between the circuit boards. In my T763 these are all black wires of about 0.8 mm diameter. It's just a shame that NAD (in Australia at least) didn't admit that this could be an issue and advise the service agents to tackle it just in case it was causing problems.