PS Audio BHK lacking..


I bought a used PS Audio BHK preamp to replace my Rotel.  It sounds thin with no depth & bass compared to my Rotel so I let it run for over an hour with no change. I'm new to tubes so I'm looking for ideas. New tubes or what?
128x128fertguy
Also check the tube voltage thing switch inside (see owners manual). Make sure they match the voltage of the tube that's is installed.
Check and make sure the amp you are using input impedance is a good match for the PS Audio preamp. If that is not a good match you will find the bass is rolled off big time.