issue with preamp

I'm not a technical guy, I like to turn it on and enjoy the sound...

My issue....I have a Rouge tube preamp when I turn it on my left channel has distortion going through it, I run mono amps....volume is turned all the way down...all inputs have distortion. I swapped out the preamp with a solid state preamp with the same cables and works fine.

any ideas?...any help much appreciated ..thanks