by EWBrown » Sun Apr 08, 2012 9:46 pm
THis actually happened about five years ago, somehow I never got around to posting it here, I'm sure that I put it under another topic,back then.
After I got some J/J KT77s with the normal, correct diameter pins, I put them into an ST-70, and had to reset the bias, as the new KT7s when just plugged in where EL34s used to be, without re-biasing, drew a somewhat lower plate current.
Even though they purportedly are considered as EL34 direct replacements, the gm (higher) and RP (lower) are sufficiently different that bias readjustment is needed in order to make them sound thier best.
They sound very nice, indeed, I took it over to a friend's house, and we ran it very hard, for several hours, and it stood up flawlessly, and sounded great! Even the J/J 5AR4/GZ34 rectifier tube had no problems, some of them will suffer a quick and gloriously pyrotechnic death ,and others will stand up to just about anything that can be thrown at them.
/ed B
Real Radios Glow in the Dark