tuner to tube preamp

I think you are right.

Try Internet radio maybe if your reception is poor due to interference.

this has to be some sort of electrical interference phenomena.
on all stations, the distortion is there, but with a cd player through the same rca inputs there is no noise. i'm just using a wire antenna, it is picking up stations well.

A few questions and comments:

Besides what has been mentioned, it could also conceivably be due to interference from something in an adjacent room, defective fluorescent lighting fixtures, or who knows what. What kind of an antenna are you using? Did you try re-orienting it? Does the noise level go down in mono mode, assuming you have a mono switch on the preamp? Is the noise level independent of signal strength (i.e., the same on distant or local stations)?

Also, I assume you are referring to FM tuners, not AM -- correct me if that is not the case.

Regards,
-- Al

What rcprince said.

Could be a bad input on the pre.

Try the tuner on other inputs and try a CD or other line source where the tuner was connected. See if the noise is associated with that one input only or not.

Have you tried another input on your preamp?