The module is split into 2 parts, a basic modulation oscillator, with a more complex carrier oscillator.
The variable harmonic oscillator has 2 outputs, F(X) and ΣF(X)dt, which are roughly equivalent to the 0 and 90 degree phase shift between Sine and Cosine.
The frequency content of the output is made up of a group of sine waves whose harmonic relationship and amplitude is determined by the Evolve control. This parameter behaves more like a tuning control than a digital wavetable oscillator, which generally scan through octave related mathematical solutions which have been calculated in advance. With a real time computer, there are settings that are not consonant, simply because there are no restrictions in what the user can access. Do not be disheartened if it takes time to familiarise yourself with the operation of the VCO. Even though the paradigm of wavetables is not new, and analogue computers were invented to solve these equations, this circuit has not appeared in a synthesizer before, and it may require patience to guide towards consistent results.
Each oscillator has two 1v/Octave inputs dedicated to it that are summed together, under the row of 4, the 2 on the left are for the Sine oscillator and 2 on the right are for the variable harmonic. The outermost inputs on each side have a switch underneath that can invert the signal (so the values from your sequencer are subtracted instead of added). The Evolve harmonic control also has a calibrated 1v/oct input with switch (be aware the Evolve 1v/oct input cannot accept negative voltages, negative voltages can only be accessed by using the panel switch to invert a positive voltage internally).
FM use is not predetermined by any internal patching, and the oscillators behave fully independently, however, the focus of the module is on dynamic ratio and dynamic depth FM patches, and use in this way may lead to some of the more unique timbres that the module is capable of.
Successful FM patches may involve using the on board multiple jack to control several aspects of the voice in parallel, for example applying the output from the sequencer to the carrier and modulator will give the same results that are found in classic FM synths like the DX7 and software based on them. An additional sequencer controlling the carrier or the modulator can dynamically vary the ratio.
The carrier oscillator is relatively limited in it’s range compared to other analogue oscillators, working at a fundamental frequency of 1hz to 6khz . Harmonic control allows output frequencies many octaves above this.
It is absolutely not unconditionally stable, and extreme settings of any tuning control, or extreme FM amounts may cause the oscillator to die out, or to get too carried away. Recovery from these extreme settings may not be immediate either. As always, patience will be rewarded, and please be assured that every step way taken for user friendly behaviour.
Current consumption: +/-250mA. Operation voltage is from within +/-15V to +/- 18V
Processing resolution: theoretically infinite.
Safe studio practice for working with electronic devices (moreso those in metal casing) necessitates 0V / signal ground on the power supply being linked to mains earth. Hinton Instruments Full Power PSU exceeds the necessary requirements for a low noise, reliable and safe supply.
Output impedances 100 ohm. Input impedances for audio and ordinary control are 10k ohm. 1v/oct are many Gigohm.
Audio output voltages are roughly. +/-5V (10V peak to peak) with the sine wave.