Later 6L6 family variant with significantly higher ratings (Pa_max 30W vs 23W, Vs_max 450V vs 400V) — not a drop-in substitute in circuits designed for 6L6GC ratings
5881 is the Tung-Sol commercial designation for the military 6L6WGB (MIL-HDBK-213A). Electrically identical to the original 6L6 with ruggedized construction for vibration resistance.
Maximum ratings are the same as the original 6L6: Va_max=400V, Vs_max=400V, Pa_max=23W, Ps_max=3W. These are lower than the 6L6GC (500V/450V/30W/5W).
Triode-strapped data from RCA datasheet: at Va=250V, Vg1=-18V, Ia=52mA, gm=5250 µmhos, mu=8, ra=4000 Ω, Pout=1.4W into 4000 Ω. At Va=300V: Ia=52mA (zero-sig), 78mA (max-sig), Pout=1.8W.
Rg_max: 0.1 MΩ (fixed bias), 0.5 MΩ (cathode bias) — applies to both pentode and triode connections.
Pin 1 is No Connection on the 5881 (glass envelope). On the original metal-envelope 6L6, pin 1 connects to the metal shell. Pin 6 has no internal connection.
Triode-strapped Pa_max is 26W (higher than pentode Pa_max of 23W) per the RCA datasheet.
Pin Layout — Octal
1No Connection
2Heater
3Anode
4
Socket-Compatible Tubes ⚠ Not electrically compatible