60-cycle hum in ART Tube MP Studio preamp

[BrotherAbel]

Howdy. I've done a search on this, but couldn't find an answer in all these threads. I'd appreciate any advice...

I've got an ART Tube MP Studio preamp and it has worked great so far (after a tube change), but when I recently started using an MXL 990 with it (with phantom power of course), it gets a very pronounced 60-cycle hum . It is bad enough to show up in the mix and mask much of the vocal part. I'm not familiar with the circuit and can't find a schematic online, so can anyone recommend a modification to significantly reduce this hum?

Thanks

 

[moresound]

Nature of the beast if your pushing it. Lay back and see if it goes away. Are you sure that it's a 60 cycle hum?
There is a reason that you can pick these up so cheap.They aren't to bad for the money though.

 

[davidtornado]

You just reminded me that I have one of these. Picked it up in Providence, RI at a guitar pedal mod shop for $80 (mine is modded, naturally). Was great for passing a guitar signal through but I don't think I ever tried using it for vocals. I know this sounds like 'captain obvious' but make sure the outlet you are plugged into is grounded. Good luck mate!