BlaknBlu - Oscar DSF

Blaknblu's Oscar DSF — All Those Classic FM Sounds You Love, Achieved With Different Math

The Oscar DSF brings something fresh to the sound of FM synthesis through its implementation of Discrete Summation Formulae (DSF). While that sounds like heavy math, the results are anything but academic - this is the sound of FM without the headache. 'DSF' synthesis is a technique that can generate many of the classic sounds typically associated with FM synthesis.

Two DSF oscillators live in this slim 10HP module. Rather than wrestling with multiple carriers and modulators, you shape sounds through two main controls: Partials and Mod Ratio. Partials build your sound from a pure sine into rich textures, while Mod Ratio - especially combined with the three-way Mode switch - defines how these harmonics play together. Switch between natural harmonic relationships or dive into more experimental territory.

Each oscillator runs through an FM-based wavefolder stage. While technically it's an FM operator with zero carrier frequency, what matters is how good it sounds. This clever design creates smooth folds that add richness rather than harshness, responding nicely to CV for dynamic textures or punchy bass sounds.

Regarding the stereo architecture — both oscillators follow the same pitch CV, but the second can drift up to an octave either way - great for subtle frequency beatings or dramatic stereo effects. A built-in VCA and panning round out the voice.

BlaknBlu hasn't forgotten about the practical details. There's a TUNE switch that serves two purposes: When on, it outputs a steady A440 reference tone for tuning other oscillators. When off, it reads and holds whatever CV is present at the leftmost VPO input. The three-position octave switch extends the range while maintaining stability. This is the sound of FM, more complex in theory, but more easy in practice!

For those of you interested in a full-on nerd-out about the mathematics and theory behind DSF synthesis, you can take a look at this excellent technical paper + a video down below that explore this concept further.

Features:

• Dual DSF-based stereo oscillator
• Sine wave wave folder
• Built-in VCA
• Three modulation modes: Free (F), Rational (R), and Irrational (I)
• Oscillator detune with ±1 octave range
• Auto-tuning function
• Dual function knobs with OSC/FOLDER mode switch
• Two VPO inputs (Volt Per Octave) with attenuators
• Stereo pan CV control
• CV control over partials and wave folding
• Dual stereo outputs (L/R)