Some AC voltage "ratio testing" shows these to be approximately 3.2K CT, with 4, 8, 16 and 32 ohm secondary taps. I'm sure they could be "ratioed" to behaving like 6.4K CT into 8, 16, 32 and 64 ohms, at least the 8 and 16 would be useful, 32 and 64 ohms for really "deaf-people" headphone amps
If the user isn't already hearing-impared, he will soon be...
I'm probably going to run the Sansui iron with PP triode strapped 6AV5GAs, and see (or listen carefully) how they sound. 2A3s / 6B4Gs in PP with fixed bias and 3K A-A OPT are good up to about 15 Watts RMS.
Maybe make them pentode / triode switchable, if I need more "juice"
These originally ran with 25E5s (PL36s) , which are the 25V filament version of EL36, which are similar to 6BQ6, which are nearly identical operating characteristics to 6AV5GA. I suppose, that if I use the original Sansui power trannie , I could try 25AV5GAs or series-connected 12AV5GAs, the possibilities are endless...
6BQ6GTB/6CU6s have a nominal 11 -12 W PD rating, but in Class A or AB1 amplifier duty, they can easily handle 18 to 20 W PD without getting all hot and bothered, and red in the plate
/ed B