by peterh Tue Nov 25, 2014 2:44 am
slovell wrote:I have an ST-70 clone with the VTA board and I have a question. I'm presently using EL34's and I'm considering rolling in some KT88's. How much power would I gain by doing so and what should the bias be for the 88's? Any opinions on KT88 tubes would be appreciated.
Thanks, Sam
If you use the original dynaco mains transformer you might get problem. This transformer
is on the limit already , kt88 will consume 1.6A filament vs el34 1.5A. This additional 0.4A
will heat the transformer and might break it.
As for power i'd say "you won't hear any difference in sound volume". As you use the same
B+ ( or even less as the transformer is loaded more) the only difference is that kt88 has
a lower impedance, this may be experienced as a tighter bass responce as the output
resistance will be lower.
In general, a power doubling is whats needed for the ear to experience a difference in volume.