I never mind comments, anybody more than welcome
C3 and C4 aren't needed for simulation, for sure, but will be with real power supply. I include them for consistency with the later production schematics...
The gain pot wiring is correct (but I may reconsider if one day I'll want to be able to mute it) , the gain of inverting amplifiers can be set this way too... by the way, the design is based on state variable filter topology, widely used in synths but not so much in other instruments or preamps: [url="http://en.wikipedia.org/wiki/State_variable_filter"]http://en.wikipedia....variable_filter[/url]
The output buffering will be needed only if the load impedance goes low enough to compete with output impedance of the opamps (which is reasonably low), and in the real world the load shouldn't go below the 10K (typical line input), so should be fine without dedicated buffers[b][color=#ff0000] in theory[/color][/b].
In practice - maybe not, that's what are prototypes for