Golden Tube Sep-1

I have a golden tube sep-1 preamp and it sounds like there is to much treble and was wondering if a bad tube in this case there is only 1 could make it sound this way, it is as if there is no bass. I would appreciate any advice.

I just had a similar problem on my Golden Tube SE-40 amp. A cap blew and the highs got pretty harsh and mids and lows seemed to drop out, but not fully.

Maybe open it up, look for something wrong. In my case it was easy to find cause the cap leaked and I saw the oily mess.

Tubes aren't that costly, $20 could get you a cheaper new one to test your theory.