A bit about Oscillator Cores.
When I first started I though that the waveforms in most analog modular VCOs were produced independently. This however is very far from the truth.
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Most VCOs derive their multiple waveforms from just 1 main waveform known as the oscillator core.
The other waveforms such as sine and square are usually produced using waveshapers.
Whenever you buy a VCO, most manufacturers will describe their oscillator as having one core or another.
There are 2 main waveforms used: triangle and sawtooth.
They are produced differently and both have their strengths and weaknesses.
They bothuse what are called integrating capacitors.
The simpliest waveform core is the sawtooth.... and thus seems to be more common.
It works on the principle that capacitors store charge. They fill up with charge until a reset voltage is reached. The rate at which the capacitor charges up is determined by the input voltage. (ie it's voltage controlled) ... this rate of charge/discharge is the frequency of the oscillator.
The triangle waveform is a bit more difficult to make as a core.
Instead of the charging/discharging of the capacitor, we have a reversing of charging current.
Both cores have a timing mechanism that resets the waveform back to its starting point by discharging the capacitor. (Then the cycle starts again).
The timing mechanism is usually a comparator. When the waveform exceeds a reference voltage the comparator triggers and the waveform resets.
The retrigger mechanism can be something like a transistor. If it is a digital timer then the oscillator is what is referred to as a digitally controlled oscillator... DCO, instead of a VCO (Voltage controlled oscillator)
VCOs that have two cores are very rare. The most obvious is that of the ARP 2500
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The 1004 has both triangle and sawtooth cores.
Both cores use a single reset mechanism.
The Buchla 158 Dual Sine-Sawtooth Generator uses a sawtooth core.
The later Buchla 258 was a triangle core dual oscillator. The 259 is also a triangle as far as I know.
The modern Buchla 261e breaks the mold ...it has a digital sine wave core. ( but the timbre section is analog).
The Roland SH-101, Oberheim Ob-Xa and Moog Memorymoog all use a Curtis CEM3340 chip.
This is a triangular core.
The Yamaha CS series VCOs use a sawtooth core oscillator.
The very early descrete component (no ICs) RA Minimoog VCOs (of which I understand only 300 exist)
used a sawtooth core.
When I first started I though that the waveforms in most analog modular VCOs were produced independently. This however is very far from the truth.
Most VCOs derive their multiple waveforms from just 1 main waveform known as the oscillator core.
The other waveforms such as sine and square are usually produced using waveshapers.
Whenever you buy a VCO, most manufacturers will describe their oscillator as having one core or another.
There are 2 main waveforms used: triangle and sawtooth.
They are produced differently and both have their strengths and weaknesses.
They bothuse what are called integrating capacitors.
The simpliest waveform core is the sawtooth.... and thus seems to be more common.
It works on the principle that capacitors store charge. They fill up with charge until a reset voltage is reached. The rate at which the capacitor charges up is determined by the input voltage. (ie it's voltage controlled) ... this rate of charge/discharge is the frequency of the oscillator.
The triangle waveform is a bit more difficult to make as a core.
Instead of the charging/discharging of the capacitor, we have a reversing of charging current.
Both cores have a timing mechanism that resets the waveform back to its starting point by discharging the capacitor. (Then the cycle starts again).
The timing mechanism is usually a comparator. When the waveform exceeds a reference voltage the comparator triggers and the waveform resets.
The retrigger mechanism can be something like a transistor. If it is a digital timer then the oscillator is what is referred to as a digitally controlled oscillator... DCO, instead of a VCO (Voltage controlled oscillator)
VCOs that have two cores are very rare. The most obvious is that of the ARP 2500
Both cores use a single reset mechanism.
The Buchla 158 Dual Sine-Sawtooth Generator uses a sawtooth core.
The later Buchla 258 was a triangle core dual oscillator. The 259 is also a triangle as far as I know.
The modern Buchla 261e breaks the mold ...it has a digital sine wave core. ( but the timbre section is analog).
The Roland SH-101, Oberheim Ob-Xa and Moog Memorymoog all use a Curtis CEM3340 chip.
This is a triangular core.
The Yamaha CS series VCOs use a sawtooth core oscillator.
The very early descrete component (no ICs) RA Minimoog VCOs (of which I understand only 300 exist)
used a sawtooth core.