Sapphire 300B

About the Sapphire 300B

The Wyetech Labs Sapphire 300B is a rugged, all-welded steel chassis monoblock amplifier designed around the popular 300B vacuum tube. It uses upgraded Shuguang 'A' Treasure 300B-Z output tubes for superior sound and reliability, complemented by rugged 5687 NOS triodes for the voltage and driver gain stages. The amplifier features a custom wide bandwidth Hammond output transformer that delivers quick, deep bass and smooth highs extending to 40 kHz. Separate high voltage DC power supplies isolate the voltage/driver stages from the output stage, enhancing signal purity. The design includes self-biasing stages with independent automatic biasing circuits for each output triode, ensuring long-term stability and sound purity comparable to single triode operation. It operates in pure Class A1 mode with no feedback, providing 18 watts RMS per channel and dynamic headroom up to 40 watts. The amplifier has selectable input impedance and gain settings, universal voltage compatibility (115/230V, 50/60Hz), and weighs 33 lbs per monoblock. Dimensions are 9.5" W x 16" L x 8.5" H. The Sapphire 300B is noted for its low noise, wide bandwidth, and exceptional sound clarity and dynamics.