Direct Digital Synthesis

Posted by & filed under Oscillators, Synth DIY.

Direct Digital Synthesis (DDS) Direct digital synthesis is a common technique for generating waveforms digitally. The principles of the technique are simple and widely applicable. You can build a DDS oscillator in hardware or in software. A DDS oscillator is sometimes also known as a Numerically-Controlled Oscillator (NCO). How does it work? The most important part of a DDS oscillator is the ‘Phase Accumulator’. This is just a counter. For example, we could use a 16-bit binary counter: When the… Read more »

Phase Distortion Synthesis

Posted by & filed under Casio, Phase Distortion.

I heard about this and could find little about it, so I started to investigate. Phase Distortion is one of those forgotten synthesis techniques that someone once built a few instruments with, and then abandoned. In the case of PD, Casio were unlikely synth pioneers to start with, and after a brief flirtation they gave up on the professional market and went back to making home keyboards. The real question is whether, if they’d stuck at it, phase distortion could… Read more »

Wavetable Oscillators

Posted by & filed under DW series, Korg, Oscillators, PPG, Synth DIY, Wave.

This page is an overview of two techniques for creating wavetable oscillators. Contents DDS – Korg DW series and similar Variable sample rate – PPG Wave and similar DDS – Korg DW series and similar The Korg DW series use a DDS oscillator scheme. Korg called it ‘DWGS’ for ‘Digital Waveform Generator System’ in the 80’s style of inscrutable acronyms, but in reality it is a single cycle of digitally stored waveform that can be played back repeatedly. It uses a counter… Read more »

Roland Juno DCOs

Posted by & filed under Juno, Oscillators, Roland.

This page is a brief look at the technology of the Roland Juno series digitally controlled oscillators. These are an interesting hybrid design. Although digitally controlled and digitally stable, the oscillator produces a true analogue output, even for ramp waves, rather than the typical staircase waveform produced by feeding an incrementing count to a DAC or from a wavetable. Here we will look at how this is done. Contents General Scheme Master Clock Counters Waveshapers Sub-Oscillator Sawtooth PWM Frequency accuracy… Read more »