Wilson,
I also have a Jolida 502 (but the CRC integrated version). I have bass heavy speakers, so I'm set up to (I think) do the opposite of what you are trying to do, but for the record: Soviet tubes from Jim McShane for power amp [I highly recommend these economical tubes -- even though I can never remember their actual name], either JAN Sylvania 12AT7WB to tighten up the base or Ei Elite Gold 12AT7 if I want more top end sparkle, & I switch between RCA long black plates and Amperex Bugle Boy 12AX7 for the rich midrange. Good luck.
Batch
I also have a Jolida 502 (but the CRC integrated version). I have bass heavy speakers, so I'm set up to (I think) do the opposite of what you are trying to do, but for the record: Soviet tubes from Jim McShane for power amp [I highly recommend these economical tubes -- even though I can never remember their actual name], either JAN Sylvania 12AT7WB to tighten up the base or Ei Elite Gold 12AT7 if I want more top end sparkle, & I switch between RCA long black plates and Amperex Bugle Boy 12AX7 for the rich midrange. Good luck.
Batch