The Befaco Octaves VCO is a 12 HP Eurorack additive oscillator, supplied here as a DIY kit for modular users who build their own modules. It stacks six square-wave pulses, each one octave apart, into a buzzy, lo-fi and retro tone. The level of every octave can be set by hand or by CV, which makes it a good fit for organ-like stacks, chiptune textures and shifting harmonic timbres.
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Six octave bands, each a multiple of the base frequency, with its own VCA
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Per-octave level control by knob or CV. A patched CV turns the knob into an attenuator
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Cascaded multi-mix outputs: use the last jack as a master mix or split the chain into submixes
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Symmetrical PWM that acts on every pulse, with manual control plus an attenuated CV input
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Hard sync input and two summed 1V/oct pitch inputs
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Octave selector and Tune Range switch for full range, one octave or one semitone of tuning
Most octave generators divide a master oscillator downwards. Octaves works the other way round. A triangle core is doubled in frequency several times, and comparators turn each triangle into a pulse of variable width. Because of this, the pulse width modulation affects every octave and moves both edges of each pulse at once. All the octaves are also centred on each other. The summed result is a symmetrical, castle-shaped waveform rather than the stepped staircase of divide-down designs, so the character of the tone is different.
The output section is built as a cascade. Each octave is summed into the next, so patching only the final jack gives you all six octaves together. Patching extra jacks breaks the chain into separate groups. If you also patch the third output, for example, the first three octaves come out of one jack and the last three out of another. You can then process the low and high parts of the stack separately, through different filters or into a stereo spread.
The front panel is heat-treated aluminium. The module is designed in Barcelona, where Befaco also prepares its kits.