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
if $10k worth of gear cant beat < $1k step #1 is to measure and baseline that it is working even remotely properly.  Both performance and settings (eg..; Bias)
The day I bought the BHK here on the Gon I ordered a new set of stock tubes from PS Audio.  They showed up a little while ago. I have them in now & they made a big big difference. It's starting to happen. I'm looking forward to trying some of the tubes you guys mentioned.
Next is what should I expect to pay. There is a set of Telefunken 12au7 on line, new for $400.