Its not clear (to me) if you reversed your small tubes. What you have described is a sound consistent with a small tube's noise floor - some are lower than others, or with a small tube that may be starting to go south.
3 responses Add your response
Heyyyyyyy, wadaya know! I noticed that (uhem) I had an ECC83 where, uh, (uhem) an ECC88 was supposed to be.
I've since re-tubed the whole thing with Pearl cryo'd SED 6L6GCs in the power section and Sovtek 6922s in place of the previous ECC88s and finally 12AX7LPSs in place of the ECC83s...
All is quite well now!
Thanks a ton for your quick observation - it saved me a whole lot of heart ache (and frustration).