The original 6L6 (metal envelope) has lower ratings than later variants: Pa_max = 19 W vs 23 W (6L6GA/GB) or 30 W (6L6GC). Screen voltage max is 270 V vs 450 V (6L6GC). Data here is for the original 6L6.
Pin 1 connects to the metal shell on the original metal-envelope 6L6. On glass-envelope variants (6L6G, 6L6GT), pin 1 is not connected. Pin 6 has no internal connection on any variant.
5881 is a ruggedised military version with identical ratings to the original 6L6. KT66 is a GEC equivalent with slightly different construction but very similar characteristics.
Rg_max of 0.1 MΩ applies to fixed-bias operation. In self-bias (cathode resistor) circuits, higher grid resistor values up to 0.5 MΩ are often used in practice, though the RCA datasheet specifies 0.1 MΩ.
Triode-strapped data sourced from Tom Schlangen's 'Pentodes Strapped as Triodes' (2009) and corroborated by TDSL push-pull triode operating data.
CV1948 is the British military designation equivalent (Brans Vademecum 1963).
Pin Layout — Octal
1Metal Shell (internal shield on metal envelope)
2Heater
3Anode
4
Socket-Compatible Tubes ⚠ Not electrically compatible