Faithful analog emulation of the VCO from the very first series of the Minimoog of which ca. 300 units have been built. Just like the original also the module is built entirely discrete with transistors, yet due to improved cicruitry the really aweful temperature stability of the Mk1-Minimoog is history. The sound is the same and the module features some modifications like PWM.
This VCO is surely not only interesting for hardcore Minimoog fans because it offers all of Minimoog's waveforms at individual outputs, also the "sharktooth" wave.
There are two selectable types of sync with controllable intensity. Besides exponential FM we also find linear FM. An other addition is the manually and voltage controllable pulse width modulation; it wasn't implemented in the minimoog and you were only able to select between fixed pulse widths.
The octave switch allows for setting the VCO in LFO mode and with negative CVs at the inputs it can oscillate pretty slowly.
The module can read internal CVs via the Doepfer Buss as long as no cable is inserted to the 1V/octave input.
The VCO is not oriented on later Minimoogs which partially used op-amps or transistor arrays with FET amplifiers - no, in this case the very early and rare Minimoogs are of interest which had tranistor based VCOs. The bad temperature stability which was caused by a design flaw in the CV summing stage was revised by AJH Synth. That means the oscillator sounds like it's supposed to and it's frequency remains stable. The transistors' specifications and values for resistors and capacitors are original.
AJH Synth brings the earliest Minimoog Mk1 into Eurorack, carefully cloning the internal discrete transistor-based circuitry, using operating and CV voltages and even modifications were included.
Same sweet sound but without the disadvantages of the original like rarity, high price, S-Trig and unstable