101D

The 101D is a directly-heated triode from the early Western Electric telephone amplifier lineage, producing roughly 0.5-1W in single-ended Class A. It is prized by a small community of extreme-fidelity enthusiasts who pair it with horn-loaded speakers of 105dB+ sensitivity, finding in it a purity and presence that surpasses even the type 45. The tube requires careful circuit design due to its very low power and high output impedance. Genuine WE 101Ds are museum-grade rarities commanding extraordinary prices, and even reproductions are limited-production specialty items.