Rega P9/Apheta Hiss/not Hum

I wonder if anyone can help with this issue. I have a Rega P9 and a Rega Apheta cartridge. I recently added a Sutherland PH3D phono stage to try to eliminate a hissing noise (this is not the typical rega hum that many report). The noise sounds very much like tube rush. It's very noticable with the volume at about 11 o'clock. When I turn the phono stage off it goes away so I know it's upstream of the Sutherland. This also happens with another phono stage I have that also suffered from RF interference. At least that's gone with the Sutherland. I have tried 3 different interconnects too with no change. The arm was rewired because of a broken tag. Brit Audio replaced the internal wiring with Cardas but left the external wiring as stock.

Does anyone know if this could be a cartridge problem? Doesn't seem to me to be a ground problem.

When I had problems with my Rega P5/Exact combo the guys at The Sound Organization (US ditributor of rega) were very helpful and diligent in trying to find out why I had some a 'hum' problem. Last I spoke with them they were very excited about the Apheta. Is you power supply close to the P9 AND is your power amp close tot he power supply?
I have a Rega P-9, Benz Silver Ref MC, Benz PP-1 Lukascheck phono, NO noise at all. Never heard of this problem with P-9.
Can't figure out how you would have noise like that... is the cartrige ground wire not connected to the pre? but that would be a loud ground hum not a 'rush'.??

Thanks for your responses. I get this noise even with the P9 power supply off. My amp is 3 or 4 feet from the TT. I spoke with the Sound Org guys too. Very helpful and pleasant to speak with.

A few people have told me it might just be the amount of gain required for a .5mv cartridge that results in some noise. Ahh the fun of analog!