Entirely dicrete VCA combined with a vactrol controlled low pass filter. The sound is gorgeous somewhere between wood and acid and the input stage can distort really well when desired. Did we already mention the lack or any ICs in the signal path? In best old school fashion this thing is built only with transistors what definitely affects the sound.
The Amplitude & Tone Controller consists of two units in series: first of all we find a discrete low pass filter with vactrol control and diode limited resonance. It is followed by a discrete VCA with manual amplitude control as well as exponenial and linear CV inputs. As the exponential CV input is normalized to the cutoff CV input of the filter you can control harmonic content and signal level with only one CV, similar to a lopass gate. All CV inputs are exipped with bipolar attenuators.
At high input gain settings the module starts to distort very nicely wich plenty of character especially with resonance turned up. Careful balancing of those two parameters allows you for blending between self oscillation and VCA distortion.