Voltage-controlled digital oscillators?

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Voltage-controlled digital oscillators?

Post by fh991586 » Wed Sep 06, 2017 5:01 pm

What is this?
Voltage-controlled digital oscillators (VCDO) - two, each with four waveforms: saw, square, pulse 1 (25% rate), pulse 2 (10% rate). Note: Pulse 1 and 2 are similar to PMW but are fixed similar to «Aelita», «Polivoks» synthesizers for e.g. Octave ranges - 3 octaves for OSC1 and 5 octaves for OSC2.
https://ask.audio/articles/the-mbs100-i ... era-synths

How do you place this between VCO and DCO?
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Re: Voltage-controlled digital oscillators?

Post by Solderman » Wed Sep 06, 2017 8:13 pm

I've seen a few Digital VCO modules for Eurorack, including using the CV for wavetable sweeps. Typically these are generated fully in software, but have a ADC used as an input interface to accept a CV signal at a sufficiently high sampling rate, in the range of that modular's standard. I suspect the AVP synth is similar, but is not designed with modular function in mind, so is less flexible. Fixed pulsewidth implies one CV interface, exclusive to pitch control.
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Re: Voltage-controlled digital oscillators?

Post by adamstan » Wed Sep 06, 2017 10:38 pm

There were also voltage controlled digital oscillators, where high-frequency VCO was used directly as a clock for the lookup table. Cymbal/hihat module from Simmons SDS-V works like this. The chain was VCO -> counter -> EPROM -> DAC.
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Re: Voltage-controlled digital oscillators?

Post by meatballfulton » Thu Sep 07, 2017 10:30 pm

It does seem pretty weird to control a digital oscillator from CV, but with a modular you don't have much choice 8-)
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Re: Voltage-controlled digital oscillators?

Post by Modulart_JP » Tue Sep 12, 2017 12:24 pm

adamstan wrote:There were also voltage controlled digital oscillators, where high-frequency VCO was used directly as a clock for the lookup table. Cymbal/hihat module from Simmons SDS-V works like this. The chain was VCO -> counter -> EPROM -> DAC.
This is how the legendary Digisound 80-21 VCDO works.
As well as our eurorack version which utilizes the same circuits and parts. ;)

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Re: Voltage-controlled digital oscillators?

Post by commodorejohn » Tue Sep 12, 2017 5:31 pm

adamstan wrote:There were also voltage controlled digital oscillators, where high-frequency VCO was used directly as a clock for the lookup table. Cymbal/hihat module from Simmons SDS-V works like this. The chain was VCO -> counter -> EPROM -> DAC.
Yeah, this seems like the most straightforward approach. Doesn't even need a microcontroller.
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