because the actual gain of a circuit depends heavily on the B+
and the resistors used, interchanging 12ax7 to 12at7 and vice versa
is not usually a problem really, just watch out for the
resulting gains change and flavor if any and see if you like it...YMMV.....
Q: why higher B+?
A: because at higher B+ cathode current increases,
a higher cathode current increases transconductance, therefore voltage gain...
Sir Tony, I found this comment from audiocircle.com and I quote:
"Good question. A general comment. The 12AT7 family has approximately 3.5 times the transconductance of a 12AX7 family. Subbing a 12AX7 for a 12AT7 will mean only 1/3-1/4 the plate current, so idle plate voltage will be much higher than with a 12AT7. Two questions emerge.
1) In an amplifier, is there enough signal voltage swing capability to drive the output tube to full power before maximum plate voltage swing reaches B+, and "flat tops".
2) As the plate current drops closer to zero, the curves become more nonlinear. More distortion.
So no matter what the circuit, conditions won't be optimal."
This is what you meant from your comment above di ba sir? I think I have to forego muna buying the Yamaha 12ax7. Baka magsisi lang sa huli. Will look instead for the real replacement for 12at7. Thanks.
