A study of Sub-Oscillators (and Oscillator Waveshaping)

Posted by & filed under Korg, Oscillators, Polysix, Roland, SH-101, Synth DIY, Vintage synths.

This article is a look at sub-oscillators, a common tactic for fattening up the bottom end, particularly  in synths with only one oscillator, or only one oscillator per voice. Classic examples include the Roland Juno 106 and SH101, and the Korg Polysix. More recently, sub-oscs turn up on a lot of modern analog synths since they’re cheap to do and can add more punch and depth. The Arturia MiniBrute, Moog SubPhatty and most of the DSI synths include them. My… Read more »

SSM2044 LP Filter designs

Posted by & filed under Filters, Korg, MonoPoly, Opera, Polysix, PPG, Siel, Synth DIY, Trident, Wave.

This page is a look at how various synths implemented the SSM2044 filter, with the datasheet design as a reference standard. I’ve redrawn all the schematics to make comparisons very easy. First, the datasheet design.   The datasheet suggests using the two differential inputs (+audio and -audio) as individual oscillator inputs for a two-oscillator synth (or synth voice). It also suggests that these two inputs should be provided with slightly different resistor values (68K Vs 100K) so that the oscillators… 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 »