zendrive_comments.txt

here there are the main differences for zendrive 2.
1) substitute the diodes in the feedback loop and put the tubes instead with anode and grid connected together as one terminal and cathode as the other one. SYMMETRICAL CLIPPING HERE
2) use a 1MB pot for gain control
3)use a 0,22uF cap as the voice control cap
4) filament of the tube powered at 9v dc

Hope to have not made mistakes