811A stereo amplifier

grabcad

A budget-friendly vacuum tube amplifier, in a SET circuit, utilizes readily available tubes from China and Russia or New Old Stock. This single-ended triode design delivers approximately 8-10 watts of power from a single 811A output tube operating at A2 class and moderate plate voltages (less than 400 volts). The amplifier's conservative design ensures safe operation with only 72-80% dissipation, while an SMPS powers the filaments and solid-state diodes regulate the B+ rail. The schematics provided offer a glimpse into this innovative design. As one author notes, Thoriated Tungsten filaments are essential for delivering detailed music with fast transients. In contrast to overpriced 300B hype, this amplifier delivers comparable performance at a fraction of the cost. Special thanks go to Andrew Whitham for sharing his expertise on 6SN7 and octal socket models.