making a MOSFET based overdrive clip asymmetrically

[mordechai]

I'm building up a vero version of the Madbean Boomstick, and I am wondering if offsetting some of the 1M resistors on the drain/gate of the MOSFETs would introduce a little asymmetrical clipping.  I think if there are three cascading stages, perhaps only a bit of an offset would be sufficiently increased in each stage to make a difference, so perhaps 1M against 1.2M or 1.5M?  Moreover, I am not sure which resistor -- the one from drain to gate or the one from gate to ground -- should be the higher or lower value.  I'd appreciate any thoughts on this, or caveats.

[GibsonGM]

Schematic??

[mordechai]

Here it is...from the PDF document on Madbean's site:

http://www.madbeanpedals.com/projects/Boomstick/docs/Boomstick.pdf

[Gus]

Why are there 1 meg resistors used for biasing the first MOSFET the input resistance is a max of 333K.

You have 1meg antipop
At a gain of one you have the 1meg antipop in parallel with ( 1meg gate to ground in parallel with 1 meg drain to gate) and as the gain goes up the input resistance goes down 

What is the point of that circuit, just to use MOSFETs that can break more easy than a BJT?

You might as well use BJTs or JFETs

[PRR]

It probably IS asymmetric.

Those Drains are not at 4.5000V, eh?

But to be sure: snip-out R10. Does that sound different?

[mordechai]

PRR...wouldn't removing R10 introduce potential damage to the MOSFET?  If not...what would be the actual effect of having that jumpered directly to ground? 

[deafbutpicky]

R10 should be removed so the mosfet can go into self bias. As it's gate won't sit on U+/2 now,
clipping will be asymmetrical. Jumpering it turns the fet off. Damage (from statics?!) is only a problem for the first stage.

[midwayfair]

R10 should be removed so the mosfet can go into self bias. As it's gate won't sit on U+/2 now,
clipping will be asymmetrical. Jumpering it turns the fet off. Damage (from statics?!) is only a problem for the first stage.

I can never seem to get a BS170 to self-bias that way. 2N7000s seem to accept it, though. Or is it different when there are multiple stages?

[deafbutpicky]

Jep, I noticed Bs170 tend to squeal, biased this way without a source resistor ,
but a small R and a bypass cap should do the trick...