(UNTESTED IRL)
this is based on a two transistor cabsim circuit I found labeled bc547, which I used a dual opamp to replace the transistors.
I also rearranged it a lil (moved the hpf to the front so i only needed to bias the first opamp buffer, and could direct couple the second buffer, reducing parts count somewhat)
It has a tone control borrowed from AMZ's website that also works as a volume knob (from unity to max gain), so that as the volume is being reduced, most of the mids are scooped first so this should sound good at low volumes as well as higher volumes.
PS - Since all of the "tone/volume" knobs action seems to be in the last 10% of the rotation, I would try a logarithmic potentiometer (A(udio)-taper) for a smooth response
