pentode

As an example, the Fender Twin Reverb[0] runs 6L6GCs[1] at 460V plate voltage, above the stated class-AB pentode max of 450V.

The guy with a 2 meter wide stall selling exclusively high end pentode valves in the old akehabera market comes to mind.

Those 6AU6 tubes are 7 pin units, but they contain only one pentode element.

Two pins for the heater, then five pins to hook up the pentode.

I wonder if there are any plans to make a higher wattage part that uses pentode design.

I've used the same tubes at a very reasonable 325V in a SET (actually single-ended pentode) hifi amp (built myself).

For an exotic example with a working web page, see this tube where two triodes and one pentode share the same one heater filament.

You could get two logic gates or one latch out of a dual pentode, so a bit-serial ALU could fit easily in a single rack.

I have also done things like use a pentode tube converted to a triode.

What beats me is the same thing in pentode+ valves and modern day transformers/gates -reuse of the same elements of the physical structure for different purposes at the same time.

>The values of total harmonic distortion to provide objectionable distortion are 2 % with a frequency range of 15000 c/s and 10.8% with a frequency range of 3750 c/s for music, and 3% and 12.8% respectively for speech, with a pentode.

The new kind of free-electron laser, uses the free electrons from a solid-state metal wire instead of using free electrons from vacuum, so it can be much smaller, much cheaper and much more reliable, exactly like a solid-state transistor is in comparison with a vacuum pentode or triode.