Axis Fuzz with a bias control pot?

[mushjoon]

Hi everyone.

I'm currently looking for a fuzz face clone that I can build but the only transistors that I have with me now are 2N3904 and 2N3906.

Fortunately, someone on this forum wrote a post about how you can build Axis Fuzz with those two transistors so I'm gonna order some missing parts for it soon.

But one thing that got me curious is whether if it's possible to add a bias control pot on Axis Fuzz so I can control how much "farty" and "velcro" vs. "smooth" I want the fuzz sound to be. 
 


This is the schematic that I'm thinking of using.

Thank you! 

[rutabaga bob]

Welcome!  Glad you could join us!  Yes, it's possible.  Several years ago, forumite DeadAstronaut worked around on a fuzz face and did a video where he could get a guitar to even sound like a trumpet, just by tweaking the bias knob.

[Gus]

The 180k

[mushjoon]

The 180k

What kind of pot with how much resistance should I replace the 180k resistor with?

[duck_arse]

easist answer - use a 100k linear pot and pad at top and/or bottom to make up the extra 80k. you may not need the padding, or you might find you only get a usable biasing range of 30% of the 100k pot - so then use a 25k or 50k pot, and then pad that to the original 180k total.

throw it on the breadboard - find what you like/what is usable - measure - build - document here.

[Phend]

Link from Fuzz Central: See smooth control. Not sure if this is what you are looking for but chk it out
https://fuzzcentral.ssguitar.com/axisface.php

[Electric Warrior]

Link from Fuzz Central: See smooth control. Not sure if this is what you are looking for but chk it out
https://fuzzcentral.ssguitar.com/axisface.php

That's a fuzz face based circuit. Totally different. He can't build that with a npn and a pnp.

[Gus]

I looked closer at the axis fuzz. The 180k I posted will not cause much change

The circuit is not that sensitive to silicon transistors used, not much of a change from 2N2222 to a 2N5889 and 2N2907 to a 2N5087 in the sim

changing the 180k will not do to much

changing the 100K from the PNP collector to ground with a fixed 10K and 100K control shows more change but still not a lot of change.