Many designers have attempted to tackle the 811 triode for audio use, but this is one complicated valve to work with!  The Dolos is the result of a five year R&D project motivated by an individual who just had to have an 811 SET amplifier, and the results are exemplary from the perspective of simplicity, performance, and tube rolling options! Each Dolos amp has only five capacitors and about twice as many resistors. There are no cathode bypass caps, there's only one coupling cap, and no global feedback is used.  An old trick first used in the Western Electric 124 amplifier and the overall high mu of the 811 make all of this possible.  Both the power and output transformers are made in the USA, the power supplies feature high lifetime Japanese electrolytic capacitors and one large polypropylene power supply capacitor for the output stage.  Coupling capacitors are Vcap and driver screen bypass capacitors are Audyn. 

The best overall performance comes from using an indirectly heated rectifier with low voltage drop like the 5AR4 when running this amplifier, as the slow starting nature helps counteract the eagerness of the 811A to conduct.  Other rectifiers like the 5R4, 5V4, 5U4, 5V3, 5Z4, and solid state plugins will work with the amplifier, though with a decrease in power for the tube options that aren't a 5AR4.  The driver tubes in the Dolos are one 6AU6 input tube and a 6V6 cathode follower buffer.  An 0D3, 0C3, 0B3, or 0A3 is used to drop the voltage that appears at the 6V6 plate to fine tune bias.

Power: (RCA 811A)

18.8W 3% THD 1kHz

21W 5% THD 1kHz

23W 10% THD 1kHz

Peak Power: 36W

Output Impedance: 1.2 Ohms on the 8 Ohm Tap

Bandwidth: -3dB at 9.8Hz and 21.5kHz

Gain: 20dB 8 Ohm Tap

Noise: Typically below 2mV on the 8 Ohm configuration