IslandPink wrote:So, what's the philisophy on this one, Steve ?
Is it to try the EL34's in a similar circuit to those you've recently built with other valves ?
Yep, that's about it in a nutshell.
I like the sound of EL34s as pentodes but in the KT120 amp, they are not really set up right. The present amp as you would expect, sounds best with KT120s.
Only thing I'm not sure about is the pentode differential input stage.
Not only do you have out of balance anode currents to contend with, there are also out of balance screen currents too.
I think the first stage, though it is a better driver for a partial feedback output stage is crying out for a constant current sink in its tail.
However, there is a 75V bias winding on the mains transformer I could make a negative supply out of, to stand the pentodes on.
That would allow a nice big tail resistor and would be relatively easy to implement.
Whether the resulting sound would be worth the bother, I won't know until I build the thing.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
