25-02-2015, 09:17 AM
The EL81 has certainly been used in audio and I assume the PL81 is identical except for the heater voltage, although it could be a mistake to assume this as the 12L6, 25L6 or 50L6 are certainly not different heater voltage versions of the 6L6, the later line output valves PL504 up to PL519 have been used in radio amateur transmitters.
John
John
