Mosfet Booster Help?

[ncusack]

Hello,

I'm working on a SHO style booster with a few tweaks and I'm getting some static coming through on heavily hit bass notes. I've just started to get into MOSFET biasing and could use some guidance. Here is a schematic of whats currently on the breadboard.

I'm looking for a Cleanish Treble boost/overdrive that lets me define the bass rolloff frequency. In this setup I get a little over 10dB full range boost with the gain pot at Min, With the Gain max the boost goes to ~25dB with a roll off around 1.5kHz as the pot on the 47uf is adjusted the rolloff drops down to around 100hz.

I think I'm probably exceeding a threshold voltage or something here and that's why it crackles a bit on the heavy notes but I'm not sure. I'm curious what I might do to prevent this from happening.

Cheers,

Neill

[GibsonGM]

Does it crackle when you turn back the gain a bit and hit the note(s)?   If not, I'd suspect you're asking too much from a single device, like you suggested, and you may want to cascade two gain stages rather than do it in one.  25dB is a lot in one go....other than crackle (clipping, maybe) I'd think you could get instability/oscillation....

[PRR]

> With the Gain max the boost goes to ~25dB

That's a gain of 18. If the bass puts-out 0.5V, you are asking 9V out of the booster.

I think you shouldn't use all the possible gain.