Apart from the two ECC83 for the phono stage (which have now been occupied by the NOS Tesla E83CC), there are also three other valves, which according to Glenn also affect the phono stage. Namely they are:

1x GE 6463 83-22 33173
1x Sovtek 7025/12AX7WA 0810
1x English electric valve 7709 CV4048 KB/QG

I wonder whether anyone thinks I could upgrade any of the above-mentioned valves with NOS ones, which can make a difference. Any suggestions?

Cheers