The only changes to the original version are to fit the signal levels to Eurorack standard. The circuit will deliver some noise when there is no input signal so it is best to patch it directly to a VCO or patch a VCA downstream. The original Buchla Timbre was the waveshaping section of a VCO so there was always an input signal.
PCB set = USD23
Panel = USD20
assembled = USD210
Build info here
Greg's dual Timbre calibration vid here