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Could you please tell me the general differences...
Antonio Melo Ribeiro
Follow Ups:
6550 and KT88 are beam tetrodes. They are very similar and usually interchangeable in most applications, although KT88 has a slight edge in terms of output power.EL34 is a pentode, with less available power but is sometimes able to be used as a substitute for 6550/KT88, provided that the connection of the tube socket caters for the suppressor grid of the EL34.
One important difference that is often ovelooked, when discussing interchangeability of pentodes and beam tetrodes, is the difference between their respective grid-to-ground resistance requirements. EL34 can tolerate about 4 times the resistance (around 470k) than 6550/KT88 (around 100k). Too high a grid-ground resistance can cause a tube to be unstable; too low a resistance doesn't matter, except that it makes the tube harder to drive. What this means in practise is that putting 6550/KT88 in an EL34 amplifier might sometimes be a bad idea, because EL34 amplifiers typically use quite high grid-ground resistance to make them easier to drive, but that may constitute an unacceptable operating point for 6550/KT88.
Thanks,I was interested in diffences in sound, but it is good to know that too...
Antonio Melo Ribeiro
Common wisdom holds that the KT88 has more power and bass, while the EL34 is more musical with better midrange.
Yes me too. I would like to know more about the sound and the substituting EL34s into a KT88 amp.
TIA
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