Voltage controlled oscillators (VCOs) are the heart of any synthesiser. The quality of the VCOs ultimately determines the performance of the synthesiser.
The two principal requirements of a synthesiser VCO are:-
These parameters are particularly important in a chording instrument where a number of VCOs are used simultaneously. In a synthesiser using only one VCO slight drift or deviation from the 1 Volt/octave characteristic might not be noticed since the ear is not particularly good at judging absolute frequency, unless a person has `perfect pitch'. In any chording instrument however, even slight mistuning is immediately apparent due to the formation of beat notes.
The ASM-VCO Core is a sawtooth-based design substantially borrowed from Electronotes and offers the builder a good quality VCO core for their own oscillator designs. Simply add input components and any wave shaping output circuitry as required.
For an absolute minimal configuration simply apply a control voltage to the 1V/Octave input and connect the Sawtooth Output to your system, apply +/-12V to +/-15V and you are up and running. See example configurations below.
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