is grid-leak the same as zero bias operation?

[funkmeblue]

in my sylvania technical manual they have what looks like the same circuit fender used and they call is zero bias operation. Instead of 10 meg, fender used a 5 meg. Any opinions on these circuits. I heard there good for dirt but how dynamic are they. How important is the first coupling cap before the 5 meg resistor, .01 uf, can it be changed to .02uf? thanks again!

[tubeswell]

Grid-leak biasing is an old-style way of biasing and is not as reliable and cathode biasing or fixed biasing. Fender did it in the early days (check out the first stage of the 5D2, which uses a 10M resistor).

Merlin has a few words to say on it in chapter 1 (page 14) of his new book - an early version of which you will find here:

http://www.freewebs.com/valvewizard1/Co ... _Stage.pdf

[funkmeblue]

ya, I'm looking at the 5a2, 5 meg resistor. I know the thd flexi 50 uses it and it's suppose so be super sensitive to stuff.