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?
fertguy-Is it possible that your speakers are out of phase? That could cause what you are describing.
No, I’ve solved the problem. It was old tubes. I’m new to tubes so I spoke too soon. surfmuz, don’t hesitate because of my screw up. Mine is sounding much better w/new tubes.
@surfmuz   It's a worthy preamp.  I ditched a VAC Ren Sig II for it, as it quite convincingly sounded truer to the music in my system.  For the money, especially used, it's a good value in sound and function.
Another big question...- is hybrid preamps like BHK much better in bass aspect then full tube units like Modwright or VAC ? Did anybody compared same price range preamps with hybrid and full tube circuitry?
Well, the BHK's bass certainly bested my VAC Ren Sig II, which retailed at a distinctly higher price range in its day.  Haven't heard a Modwright preamp.  I'm guessing the BHK's MOSFET output gives it bass authority, but you can play with tonal character with tube choices, so.....