Al - yes I installed a 100ohm resistor on one leg of the primary side of the filament transformer. And I did not change that value when changing from Eml to Sophia.
My vintage Stancor filament transformers are rated for 117v.
These trannies have a center tap so I can bias through it and avoid a bad sounding hum pot and still use a/c heat. I have no 60hz hum but if I put my ear to the speaker I hear what I believe to be a harmonic of 60hz which is 120hz. At least that is what I think I am hearing. The ELM tubes are so well balance a hum pot was not needed. But I was not so lucky with the Sophia which I could not use with out installing a hum pot.
When I removed those hum pots this amplifier came to life.
I would not feel comfortable running these tubes much above 1% which is 5.05v.
My vintage Stancor filament transformers are rated for 117v.
These trannies have a center tap so I can bias through it and avoid a bad sounding hum pot and still use a/c heat. I have no 60hz hum but if I put my ear to the speaker I hear what I believe to be a harmonic of 60hz which is 120hz. At least that is what I think I am hearing. The ELM tubes are so well balance a hum pot was not needed. But I was not so lucky with the Sophia which I could not use with out installing a hum pot.
When I removed those hum pots this amplifier came to life.
I would not feel comfortable running these tubes much above 1% which is 5.05v.