Try some old Red Base RCA 5692 - the very best 6SN7 there ever was. The go for about $100 on average
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F174260219898
These are what your looking for - just as an example - no affiliation with seller - proceed with the usual caution
Good Listening
Peter
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F174260219898
These are what your looking for - just as an example - no affiliation with seller - proceed with the usual caution
Good Listening
Peter