Thank you KMG.
So.. R2 (1K), D1, D2, D3 and D4 are "SET" values to emulate the 12ax7 response right? There is no need to play with them?
What do you mean by "Point of Clipping"? the negative grid bias voltage like -1.5v in a 12ax7?
With what Resistor the Capacitor forms the RC filter? R?1 or R?2 or together?
Do they effect only the frequency or the grid (gate) auto-bias point also?
Can you please elaborate more about replacing a 12ax7 gain stage with an lnd150.
For example:
* How to calculate the Cathode Resistor & Bypass Capacitor in the lnd150 gain stage to be equivalent to the 12ax7.
* How to actually bias the Gate of the lnd150 to be equal to the auto-biased grid of the 12ax7.
* How important are the values of all the diodes in the circuit and what they actually for.
* Why we need a Negative voltage at the Soure.
A document like this:
http://www.freewebs.com/valvewizard1/Common_Gain_Stage.pdfWill be SUPER effective in terms of explaining the "How To"s.
And most important:
Can we actually place 2 gain stages like these (with access to some pots) into a 12ax7 shape clear plastic enclosure and stick it in any 12ax7 place?
Patent it maybe?

I greatly appreciate the info here.
Thanks.
P.S.
к стати, Я так плохо читаю по руский что не надо даже пробовать.
Some Translit.ru help here took me about 10 minutes.
