Based on this FSB schematic
I've added a bright switch for the Treble channel to tame it a bit when not blending in the Normal channel.
To omit the bright switch, remove the 330pf at the bottom left corner (or just leave it in) and replace the 100pf with a 470pf.
Requires a switchable 9/18 volt supply like one of these
My build with the power supply combined with an Optotron bypass as seen here
1978 Gibson Les Paul Standard, Cherry Sunburst