6H30 (or 6N6)? Might mate well with the slightly romantic sound of a 300B. Something like 12-13ma, bias the lower tube around 4 volts, shoot for low 200's on the top tube's plate...I forget your B+ but maybe around 14K-12K load resistor? Also consider ditching the resistor between the two tubes and biasing the top tube's grid from a voltage divider (Allen always hated me showing self biased cascodes). Don't forget grid stoppers and do float the upper tubes heater with B+ voltage divider:) Might be better as a direct coupled cascade with a 1:1.25 IT to the 300B but now we have a different amp (and no place for your grid chokes).Totally agree that ears alone are not enough and also think in this day and age a computer based testing system makes sense. But you still need a rather good sound card and I'd say at least 16 bit resolution (on the PC scope part)....so it still isn't cheap by any means. Besides we would drive ourselves crazy with FFT plots and THD values...LOL!
Russ
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