It looks as a pretty good amp without any modifications. You can get nothing better changing it from ultra-linear to triode mode, just less power, that's it.
I thought it looked OK myself, pro input appreciated, unfortunately all thats left in supply box are two ASL PT30's someone had them rewind without the ultra taps, so I guess I will try it as triode connected and aim for 17-18 watts.
If the power trafo has some extra filament current, ditch the 12AU7 and install a 6FQ7/6CG7. The 'U7 has linearity issues.
Another easy upgrade is to replace the 1Nnnnn diodes with the corresponding UFnnnn parts. UFnnnn diodes are MUCH quieter than the corresponding 1Nnnnn parts.
Another easy upgrade is to replace the 1Nnnnn diodes with the corresponding UFnnnn parts. UFnnnn diodes are MUCH quieter than the corresponding 1Nnnnn parts.
Thanks for the advice, the transfomer I have is 360 V 200 mA - good for 450 or so DC but sadly specd for 3 amps 6.3 and another winding for 1 amp 6.3 - obviously good only for AC heater supply. Found some 6.6-6.6 CT toroids at All electronics, 8 amp rating, got em, they are powertronix, well made 🙂 and work to specs - so, now I do have enough for a good DC heater supply. Will try the swap. Have the board half populated, now just have to see what that plate resistor on 12ax7 really wants to be. At the rate I am going won't be done for a month, but I will let you know how it sounds.
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