Hammond made an OPT for me similar to their 1650N but with half the impedance.What would be a good OPT for that amp?
As it happens my vers of Crowhurst's Twin Coupled Amp has been on the test bench for the last couple of weeks. When I get a chance from pushing snow & fixing things around the place I fire it up & do some tests. So attached are some of the results.You can also use two "OT" xfmrs in the Norman Crowhurst "Twin Coupled" arrangement, to get doubled primary voltage, inductance and power. With the 50% CFB you get with that scheme, any V reg. tubes (6080, 6AS7, 5998, 7236, 6336, 6528... ) will shine like 300Bs, from the inherent high linearity mode. (which V reg tubes aren't generally known for, although P-P helps a lot) ( I would suggest using the high gm 6528A for CFB mode, to keep the drive voltage reasonable )
That all depends on voltages. If you use a 300V B+ you'll have crap bass. If you use 150V B+ it'll be fine. Also I have a driver that swings enough to drive it a cathode follower - and berfore you say "but where do I get 600V?" a quadrupler off 120V or a doubler from 230V... A tripler from 120V gets you close enough, too... Also the 47uF/600V cap is B43541B8476M000 from TDK but you could use a series pair... I redesigned my boards to use a pair to avoid a single source part.It'd work, buy you'll have crap LF power.
No problem for the low frequencies, that depends on a low rp, the 6AS7G & 6080 have that,
High frequency still a problem due to leakage inductance.