6SN7 / 6L6 DIY Tube Amp

The valve lineup for each channel is a 6SN7 as first amplifier and phase splitter, followed by another 6SN7 driving a pair of 6L6s. Bias is set by active semiconductor current sinks. The 400V HT is generated by a double anode diode (5R4) driving a choke input filter. The audio output transformers are Hammond Manufacturing 1620s. With a conservative rating of 20W per channel, measured frequency response is 10Hz to 40KHz with minimal square wave overshoot. I'm very pleased with how this unit sounds and looks.

Schematic Drawing: Williamson 6SN7 - 6L6 (KT66) Tube Amplifier