I am considering building this amp. What are your opinions on the schematics?
Single Ended 6K6 Amplifier – a Gift! | Evil Science Audio
Single Ended 6K6 Amplifier – a Gift! | Evil Science Audio
Too much 2nd harmonic distortion. The 'T7 has linearity issues. The 6K6 appears to be wired in ultra-linear (UL) mode, but loop NFB of some kind is not employed. Damping factor will be inadequate for many speakers.
IMO, with tweaking, a linear and adequately damped result can be achieved. CCS load the 'T7 voltage amplifier and eliminate its cathode resistor bypass capacitor. Keep gain up by buffering the voltage amplifier with an enhancement mode MOSFET source follower DC coupled to its plate. Add a GNFB loop from O/P "iron" secondary to voltage amplifier cathode.
IMO, with tweaking, a linear and adequately damped result can be achieved. CCS load the 'T7 voltage amplifier and eliminate its cathode resistor bypass capacitor. Keep gain up by buffering the voltage amplifier with an enhancement mode MOSFET source follower DC coupled to its plate. Add a GNFB loop from O/P "iron" secondary to voltage amplifier cathode.
Looks good. Keep it simple. Maybe add GNFB for some fun. Pull the driver bypass cap and use 8K resistor (to start) back from the the OPT secondary (+).