Phono input ground hum

[Peter]

Hi All, I've recently assembled a TT setup with Pro-Ject RPM 5.1 (TT), Pro-Ject Stereo Box Phono (AMP), and 2 Wharfedale 220 speakers. When I plugged everything in, I noticed that my right speaker is humming (ground hum). After checking that I've connected the ground to both the TT and the amp (they were indeed connected), I've disconnected the TT from the amp, but the hum didn't go away (the right speaker is humming when the cord is connected to the amp, but not connected to the TT). The hum is not present at the auxiliary inputs (checked it when I connected my laptop). Therefore, I would assume the problem is in the amp phono in. Is this a common problem, or is the amp malfunctioning (or could it be the ground RCA cable problem)? Also, the hum subsides a bit when the aux port from the amp is connected to the laptop, which indicated only further that grounding is the issue.

Thanks.

 

[brownz]

What interconnects are you using between the turntable and the Phono Stage ? A friend of mine bought some interconnects that have a floating shield which means the screening isn't earthed to the RCA. As soon as you plugged the cables into the Phono stage you would get a godawful hum, which dissapated when you connected them to the turntable, but wasn't completely eliminated. I'd seen this before with these cables so wandered along with a cheap set of decent phono friendly interconnects, and he was gobsmacked ! I used to suffer from a bit of ground loop hum (shonky medieval house wiring) with my RPM1 Genie, but since I ran a cable direct to the mains earth from turntable > phono stage > amp it's impoved things no end. You can buy a special Earth Plug that will allow you to do this. Good luck in tracking it down.