Last summer I hooked up my trusty mid/late-80s NAD 3020e amp to a new Audio-Technica AT-LP120XUSB turntable and a pair of Mission LX-1 speakers (recommended by folks here) and have been thoroughly enjoying playing records for the first time in about 30 years. But recently I've been noticing an intermittent buzzing noise which I think is coming from the amp. It's not the big start-up noise a bit like a fart (sorry to sound childish), but an intermittent kind of high-pitched noise while playing records. It seems to come on and go off at its own will, but there must be something triggering it. Does anyone know what it might be? It doesn't seem to change due to the volume, which I rarely have above about 2/2.5ish on the dial. Could it be a lose connection somewhere, or some kind of interference that I might be able to cut out? OR, perish the thought, could it just be that really old amps do this, and it's time to think about getting a new one?? Any tips would be greatly appreciated, thanks.