6B4

Octal 8-pin directly-heated power triode operating on a 6.3-volt filament, highly prized by audiophiles for its warm, remarkably transparent single-ended or push-pull audio power output. Equivalents: 6B4G, 6A3 (different socket base). Real-Life Examples: Vintage post-war high-fidelity amplifiers, classic theater sound system amplifiers, custom single-ended triode (SET) audio amplifiers.