91-01 300B SET Monoblocks

About the 91-01 300B SET Monoblocks

The Sophia Electric 91-01 300B SET Monoblocks are hand-built, single-ended, directly heated triode power amplifiers designed around one 300B output tube per monoblock. The circuit operates without global negative feedback and uses a 6SN7 dual-triode driver and 5Z3PA full-wave rectifier. Sophia Electric designs and manufactures the power and output transformers in-house. The amplifier uses autobias, separate heater hum-adjustment controls, and transformer-coupled speaker outputs for 4- and 8-ohm loads. The standard model is rated at approximately 8–9 watts per monoblock, making it most appropriate for efficient loudspeakers. Available documentation also describes a Super Quiet version and later Signature 91-01 variants; those should not be assumed identical to the standard model.