6ER5
250V
Eb 197V, -2.5V, Ib 2.4mA, RL 22k, gain 30
Max input signal is ~1V pk-pk.
6FH5
It seems impossible to come up with a linear op point using a B+ of less than 250V with this one.
250V
Eb 135V, Ec -1.5V, Ib 7.66mA, RL 15k, gain 32
Eb 137V, Ec -1.0V, Ib 11.3mA, RL 10k, gain 30
The second one above is almost exactly that given as the tube manual class A amplifier point, so I feel confident saying
that: rp 5.6k, gm 9000 umhos, mu 50. Max input signal is ~1V pk-pk.
6GK5
250V
Eb 122V, Ec -1.5V, Ib 3.55mA, RL 36k, gain 50
300V
Eb 118V, Ec -1.5V, Ib 3.87mA, RL 47k, gain 55
Eb 193V, Ec -2.0V, Ib 8.23mA, RL 13k, gain 45
Max input signal is ~1V pk-pk in all cases.
6J4/8532
5755
A computer tube, also used in power supplies as a DC amplifier. Runs at astoundingly low plate currents.
250V
Eb 170V, Ec -2V, Ib 0.08mA, RL 1M, gain 60
300V
Eb 234V, Ec -2.5V, Ib 0.3mA, RL 220k, gain 42
Eb 179V, Ec -2V, Ib 0.12mA, RL 1M, gain 60
Max input signal before distortion is ~1V pk-pk in all cases.
Might make a good phono input tube due to low current and its anti-microphonic construction.
5965
This computer tube has been used in a few audio circuits lately - and I did find a few good operating points.
250V
Eb 182.5V, Ec -5V, Ib 1.2mA, RL 56k, gain 22.5
300V
Eb 208V, Ec -5V, Ib 2.35mA, RL 39k, gain 25
Eb 80V, Ec -2V, Ib 1.0mA, RL 220k, gain 33
Max input signal without encountering serious distortion is ~2V pk-pk in both cases.
The 80V operating point in particular would be most useful direct coupled to a split load inverter, or cathode follower.
This UHF triode is most usable in the 8532 and 6J4WA versions due to microphonics in the 6J4 version.
150V
Eb 90V, Ec -1.5V, Ib 4.0mA, RL 15k, gain 31
250V
Eb 113V, Ec -1.5V, Ib 7.6mA, RL18k, gain 38
Max input signal ~1V pk-pk in both cases.
