Thanks Mitch!
Here’s a simple note I put together on my TubeHead:
http://www.jensign.com/TubeHead/ I also was interested in the feedback t-network used in the inverting op-amp circuit … probably to achieve the high gain in an inverting amp config. with a fairly high effective input impedance. At any rate, I wrote a generic script calculator for a single stage amp with default values more or less right for the 1st stage of the TubeHead:
http://www.jensign.com/TubeHead/calc.html