More dirt, but not more volume - suggestions?

[markeebee]

I'm building a request for a friend, it's a sonic stump with a mid tweak knob.

He also would like to be able to add a bit of crunch. Not metal grrrrrrr, but r'n'b country twanggggggggg.

I wanna try to keep it down to four knobs, so I'm trying to remember a SIMPLE one knob drive circuit that doesn't hike the volume much while adding a bit of jangly girth. Needs to be skweeky clean at one end, rageddy at the other.  And I haven't got a lot of space.

I'm thinking SHO with a trim pot to limit the output.  Any other nice suggestions?

[R O Tiree]

How about arranging an opamp output buffer with the gain controlled by one half of a dual-gang pot... the other half of the pot will control the gain of the SHO. Wired up so, as one gain (SHO) is turned up, the other (output buffer) goes down. Suitable choice of the other resistor on the opamp might well ensure constant output amplitude. You might have to play games with RG's article about setting the taper of that pot with an external resistor to ensure that the vast majority of the gain reduction on the output buffer happens while the MOSFET is producing clean output and very little more reduction happens as soon as the MOSFET starts to clip.

If you post the schem you're using (lots of variations on a theme out there on the interwebs), then I'll have a play in sim and see what I can come up with. Socketing the resistors will enable you to "tune" it to suit the particular MOSFET you are going to put in there (or maybe breadboard with pots and then select accurate resistors for the final build?).