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?
As tubes age they at the 'end of their lives' sound pretty lackluster.The gold lion tubes that PS Audio recommends are fine tubes but emphasize the mids and bass.A faster sounding lively tube is the JAN Phillips 12AU7.It's one to put on your list to try.
Hi fertguy

If you try some high quality nos tubes in the BHK Signature preamp it will transform that preamp into a very good sounding preamp. Either a 12 volt 12au7 from either Telefunken, Mullard, Amperex or Siemens from the 50’s or the 60’s should sound great. If you change the two jumpers to the 6 volt settings and the 5 milliamperes bias settings then either a pair of 6922’s, 7308’s or 7dj8’s will sound great as well. BHK’s favorite tubes are the Tungsram 7dj8’s from the 60’s. Any of these nos older tubes will elevate that preamp to a whole new level. Best of luck.