This my eight design, 3rd 300B, slightly different from the TB300B proposal with the bias adjustment (an attempt to squeeze power to 7 watts), will use non inductive high power resistors. Modification 0 will exclusively use Tamura F series transformers.
MY apprehensions,
This configuration have been successful with the TB2A3 and it will show good bandwidth (TB2A3 prototype have good performance on the lows a sign of over engineered trannies, its objective inductance was initially set at 50H if my memory serves me right). BUT, will the 2A3 beat the crap out of this 300B incarnate.
So I tried to hedge my bets on this design
a.) I eliminated phase shifting components in the signal chain as possible
b.) weakest link are R7 and C1A
c.) R7 will be a candidate for a grid choke, may try the silk audio grid choke in modification 1 series
d.) May lower C1A for 2uF-3uF non doubling mode rectifier, recalculating the voltage budget and that brings us to
e.) R2, the cheat tweak, if I need to swap C1A in mod 1 or mod 2 and recalculate the voltage budget, I do not need to resolder, all i need to do is recalce the value of R2 and reset it to that objective voltage! viola!
Lastly, I may need to drive this with a variac as tamura provided 230V transformers !?1*@#$?!
I have my cad guys eugene and kevin layout the chassis, will update on that progress soon.