Best mellow sounding 12ax7 for Thor TA-1000 preamp


I just bought  Thor TA-1000 and am very impressed with the resolution but want it to be more mellow sounding... Darker and less treble emphasis. Can anyone recommend the most musical but mellow/organic 12ax7 for the Thor? When I bought it the unit has telefunkens. The outputs are already mullards so I am focused on the inputs.

It is feeding vtl mb-185 signature amps and quad esl63 with vandersteen 2wq subs.

Thanks!
montaldo
Probably not very useful but my mark I serial number is in the 200's. I dont know when the mkII started.

The only switches I could imagine would be either a USB/rca input switch (does it have a USB input?) or a phone mm/mc switch, if the preamp is a ta-2000 with phono.




I have an owners manual I can scan and email to you if you still need it. 

My TPA-1000 Mark II serial number is 231
I actually do have a manual I can scan and email if you still.want it. Old thread, I know.
I own a Thor 1000 with a Khozmo attenuator and V-cap upgrades. The unit came to me with Russian 12AX7 and 12AT7s. These sounded terrible. So I changed to a pair of Telefunken 12AT7s and Raytheon Windmill 5751s. The old stock tubes were much better however I really think that an old stock 12AX7 like an Amperex would be better. I think that the lower gain of the 5751 robs the Thor of a bit dynamics making the Thor less concise. If you want to tone the Thor down a bit I wouldnt suggest Telefunken AT or AXs. My favorite 12AT7 are Amperex.