I've been playing with this (one stage only).
(http://www.diystompboxes.com/pedals/mosfet.gif)
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?
(http://www.vt52.com/diy/diypage/aren/zenbride/zenbride_sch1.jpg)
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.
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
Quote from: bool on April 22, 2014, 06:04:17 AM
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.
Quote from: bool on April 22, 2014, 06:04:17 AM
"Schade-ing" the mosfet in one go
I think that "Schade-ing" is THE way to go!
Quote from: bool on April 22, 2014, 06:04:17 AM
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! 8)