Hum issue on Cambridge Audio 540p

[richie60]

Can anybody tell me why I get a hum when I ground my turntable directly to the Cambridge audio 540p Phono preamp?

If I use my Rega fono, it's fine, but when the 540p is in use I have to ground directly to the main amp to eliminate hum.

[walpurgis]

It's probably a hum loop. I wouldn't worry too much about connecting an earth from the turntable unless you really feel a need. It's possibly already earthing through the signal lead. There's no reason why you can't earth to the amp if you choose. Each phono set-up seems to have its own needs.

[richie60]

Thanks for the info. Just wondered why two Phono amps would be different unless the 540p is faulty.