P-channel MOSFET instead of N-channel = less noise?

[bassmeister]

Joe Davisson states on http://www.diystompboxes.com/analogalchemy/pedals/obsidian.html that "...I found the P-channel counterparts to be much less noisy, on the order of 5-10 times..." in his own design Obsidian. He is referring to the BS170 (N-channel MOSFET) vs. the BS250 (P-channel). Could this reasoning be applied to other designs as well where an N-channel MOSFET is originally used, i.e. switching to a P-channel equivalent would result in less noise?

I was thinking in particular that the AMZ mosfet boost perhaps could be less noisy if a BS250 is used. You would of course have to supply -9V and reverse the polarity of electrolytics (nothing else as far as I can tell from the schematics). The difference is that the Obsidian uses three cascaded stages, so noise builds up. I don't know if noise already is low on the single class A stage of the AMZ mosfet boost.

[bwanasonic]

I don't know if noise already is low on the single class A stage of the AMZ mosfet boost.

Yes, it is quite low. Not worth the hassle of a neg. supply for this one.

Kerry M

[R.G.]

Joe Davisson states on http://www.diystompboxes.com/analogalchemy/pedals/obsidian.html that "...I found the P-channel counterparts to be much less noisy, on the order of 5-10 times..."

That's bizzarre. I can't think of any substantial reason why that should be so unless the circuit he put them into was causing additional noise.

I'd have to see a lot more real world data before I started trying to use P-channels because P-channel is quieter.

[lovekraft0]

Joe Davisson says it's a product of manufacturing processes:
http://diystompboxes.com/sboxforum/viewtopic.php?p=36888
I have heard elsewhere that N-channel MOSFETs are noisier, but I've also been told that getting the polarity right when installing  Orange Drops is critical.