Doepfer A-111-3 Micro Precision VCO

The Micro Precision VCO is a space-saving and utterly precise analog VCO / LFO with a extremely wide frequency range, immaculate tracking over at least ten octaves and nearly perfect waveforms.
Basically, it is the same circuitry like the High-End VCO A-111-2 but with reduced functions and controls. It is suitable as a modulator for exact linear FM and much more.

The A-111-3 has two elements for setting the frequency: A switch selecting between LFO and VCO mode as well as a tune control with a jumper-selectable range:

• Jumper position 1: 16Hz to 20 kHz
• Jumper position 2: 16Hz to 70Hz
• Without jumper: 16Hz to 22Hz

The XM potentiometer can be used as a fine tune control as long as nothing is patched to the XM socket.

The oscillator has a frequency range of at least fifteen osctaves (0.0001 - 40 Hz in LFO mode; 0.5 Hz to 20 kHz in VCO mode) and offers perfect 1 V per octave tracking over ten octaves minimum, typically in the range of 20 Hz to 20 kHz. Frequencias below 25 Hz are visualized with a two-color LED.
The 1V per octave input is accompanied by two FM inputs, one for linear and one for exponential frequency modulation. A jumper determines whether the module obtains pitch CV via the internal bus.

The VCO has a triangle core from which sawtooth, pulse and triangle are derived. The wave forms are almost perfect and sans glitches.
The pulse width can be set with a control from 0 to 100% and of course it can be modulated.
There is one input for oscillator synchronisation and its type, either hard or soft sync, is jumper-selected. Both types differ in sound with the hard sync being more aggressive and richer in harmonics.