Buzz or hum


I have a hum in my system, Will Vincent amp, PS audio preamp with gain. and Coincident speakers.The buzz does not go up with the volume. When I unplug the RCAs from the preamp that go into the amp the buzz stops. I also plugged in my CD player directly in the amp and there was no buzz. So it is somewhat isolated to the preamp, I guess?
Someone said I might have a grounding issue but how would I fix that?

Thanks
coryb
Float the ground in the preamp (those little 3 prong adapters)...not a big deal. My preamp/amp combo used to hum and that's how I solved it until I bought a different preamp (Kavent S-33) and it's weirdly 2 prong. I also use the ground lift switch on my REL sub and it works fine.
It does sound like a ground loop or 60 HZ hum. Chassis grounding usually solves this problem.
I love these threads it gives me the opportunity to use my old adage, again. " why did the amp hum, because it didn't no the words ".
I have to mention (well...I do) that I scored a NOS PS Audio Humbuster. A great thing that works exactly as described for mechanical hummage. That's right...hummage.