Charles/Joe,
Thank you for the useful discussion about the tubes on the Frankenstein Mk ii. I just want to add my 2 cents because I had chance to try some rectifiers (RCA 5U4GB, Tung-sol 5U4GB, and EML 5U4GM), and output tubes (Psvane 300BT, 300BT-II, EML 300BM, and Takatsuki TA-300B).
To my ear, the Tung-sol/Takatsuki was the best by far out of all the combinations I have tried.
Rectifier: the RCA 5U4GB was the close second. As for the EML 5U4GM...I don't know... it added little more bass to my system, but that was all. It immediately killed three dimensionality, dynamics and transparency which had been easily conveyed by the Tung-sol.
Output tubes: In my system, the sound from Psvane was fast and nimble which I enjoyed. EML 300BM added more liquidity,musicality and authority in the bass, but it was not my cup of tea-little too slow. Takatsuki? As soon as putting them into the slots...I immediately talked to myself; That's it. Beautiful texture in every frequency range, significant musicality, no artificial exaggeration at the bottom (which I felt from EML 300BM), but still fast and tight notes with excellent tonal balance. I think this is the very best.
By the way, have you ever tried HiFi Tuning Supreme fuses for the amp? I would appreciate if you can give me any comments on that. Do you know the specfication of stock fuses?
Thanks!
Wu