• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Triode vs Pentode cathode followers

I have been playing with a lot of a KT-88 or 6550 cathode followers and for some time have been enjoying the Triode connected 6550EH output tubes as duty in my headphone Amp as an output stage.

Some time ago I read an article in Tube CAD about pentode based cathode followers and so I wanted to investigate this further and since only simple rewire is all it required to go from triode to pentode on the same platform I could evaluate the sound and performance differences between the (2) two. So far the only measurements I did was noise and the pentode connection reduced that from 2.2 mV to 0,7 mV Hum was totally gone in pentode mode yet was noticeable in triode mode however a regulated power supply would have made both quiet. Maybe?

I thought I would share this with you. The attached schematic shows actual measured voltages with the 6550EH tubes with about 500 Hours on them.