I have a Pro-Ject 1.2 turntable, fitted with an Ortofon OM10 cartridge. It is connected to a JVC receiver of mid-seventies vintage.

I am getting an annoying buzzing noise, which is always present but increases in intensity when playing a record or when the tonearm is suspended over the playing surface. It is not particularly loud, but it is quite distinct during quiet passages. It is audible through both channels, but is perhaps slightly more apparent in the right channel.

A little experimentation yielded some interesting results. Unplugging the turntable's mains plug almost entirely eliminated the noise. Futhermore, unplugging the receiver at the mains also made the buzzing diminish drastically during the couple of seconds it takes for the power supply capacitors to discharge.

I've checked everything I can think of - the turntable ground wire is attached to the ground connection on the receiver, and the cartridge is also securely connected. I tried using a spare cartridge that I have (same model), but obtained exactly the same results.

This one has me stumped. Can anyone offer any suggestions as to what the problem may be?