Power Mosfet gain stages

[tca]

I've been playing with this (one stage only).



Why biasing the mosfet with a voltage divider to voltage source instead of self-bias from drain? The self-bias arrangement seems more adapted to any device and parameters variations?

Actually Nelson Pass, in the Bride of Zen preamp, does the same?



Is it a way of getting some kind of particular distortion? I've tested both topologies and I do prefer the sound/distortion that comes out from the self-bias way!

Thanks.

[bool]

me too...

although it's much easier to get a "fixed" (non-miller'ed) input impedance with a fixed bias, espec. with small mosfets (read 2n7000 etc).

basically, with the self-bias you are also "Schade-ing" the mosfet in one go, if you aren't blocking the AC component within the FB loop .. http://www.clarisonus.com/Archives/TubeTheory/Schade%201938%20Beam%20Power%20Tubes.pdf

so.. good luck, IRF7xx are particularly "analog" sounding because of their larger gate charge

[tca]

it's much easier to get a "fixed" (non-miller'ed) input impedance with a fixed bias, espec. with small mosfets (read 2n7000 etc).

Yep, but it really needs to be a power mosfet, my booster is running at 140mA.

"Schade-ing" the mosfet in one go

I think that "Schade-ing"  is THE way to go!

so.. good luck, IRF7xx are particularly "analog" sounding because of their larger gate charge

I know that, some IRF8* and IRF6* will also work the way we want!

And, btw, there is no such thing as luck!