Help - I've got an Ocean in my Phono Stage

I'm using a Rega P3 and a Denon 103R cartridge, with a Monolithic PS-1 Phono stage.

The PS-1 just barely has enough gain to handle the Denon cartridge - I've got to max out the gain on it.... however I'm getting this loud background hiss/hum sound that sounds kind of like the ocean at night. I really thought the problem was with the Rega, because I recently rewired it. However, on a whim, last night I unplugged the Rega from the Monolithic and lo and behold - still getting the noise.

I've tested all of the inputs on my pre-amp and amp... so I know that the hiss-hum-ocean sound is coming from the PS-1.

I've tried moving the PS-1 and changing the outlet the power cord is plugged in to.

I know that I've got a lot of RF in my listening area - but am curious why it might only affect the PS-1...

Any ideas on how to fix this problem (like buy a new phono stage that can handle a low output MC cartridge) would be appreciated.

thanks,

ljg