Dogbotic Workshops
Ondes VCO - Therevox

Ondes VCO - Therevox

by Sam Chittenden

The Ondes VCO by Therevox is a 14hp oscillator with classic vibes and a classy look. It’s a recreation of the oscillator circuit found in the 1975 version of the Ondes Martenot, the enigmatic electronic instrument originally designed in 1928 by Maurice Martenot. Therevox used some of the original hand-drawn schematics when designing the Ondes, but added improvements for its port into the Eurorack format.
Aesthetically the Ondes has a neo-vintage look about it with a powder coated, solid aluminum panel, robust feeling sliding switches and a large, smooth tuning knob. Unlike most Eurorack oscillators on the market today, instead of individual waveform outs the Ondes instead has 3 identical output jacks— a nod to the diffusers which were different styles of external speakers and resonators that provided differing tones and timbres depending on their construction that were typically used with original Ondes Martenots. Here, in the same spirit it allows for multiple output paths and separate signal processing. The Ondes VCO mixes its waveform internally via a series of switches which are arranged along the top half of the module. In the top row—in addition to 3 individual switches corresponding to the three output jacks—there are seven which toggle different waveforms in or out of the output mix, identified only by single letters or numbers on the panel but with full descriptions and titles in the simple but informative manual. The Tutti switch [labeled “T”] is a preset mixture of all the waveforms and is the only switch that when activated will override the other switch settings. The remaining waveforms [when T is off] are Gambe—an asymmetrical square wave, Octaviant—a rectified sine wave, Nasillard—a narrow and fixed pulse wave, Creux—a soft clipped triangle, Onde—a fairly pure sine, and Petit Gambe—a low-pass filtered square wave. The Octaviant [“8”] and Petit Gambe [small capital “G”] each have a dedicated volume slider and associated VCA. The lower half of the module contains the output jacks, a fine tuning knob [with a range of about 1.5 octaves], and a four-position octave switch.
In practice, the Ondes VCO is somewhat of a macro oscillator and there are a certain amount of limitations inherent in the sound sculpting available. It’s a manual affair when tweaking the tone of the oscillator as the only voltage control is over the mix level of the Octaviant and Petit Gambe waveforms. The other four are either on or off [and Tutti is a fixed preset] so adjusting the relative levels between each waveform is impossible. Despite its simplicity and the lack of extensive CV inputs the Ondes VCO is quite capable of producing beautiful and rich textures and timbres. The curated tone of the Tutti waveform has a nice buzz and some good weight behind it with plenty of harmonic fodder for filters to chew on. The Creux and Onde waves provide a nice solid bed of fundamental frequencies and more harmonics can be added to taste with the Octaviant and Petit Gambe sliders. Each waveform’s dedicated VCA and slider allows for slowly evolving timbres or rhythmically punctuated harmonics to be added dynamically in the mix, and patching a noise source or another oscillator running at audio rate into either VCA circuit is a great way to get more aggressive and dirty tones.
Despite the relatively small amount of voltage control options, I like the Ondes VCO. The on-panel labeling of the included waveforms are a bit cryptic, and the lack of voltage control can be limiting, but the simple controls mean you’re not going to get lost in this oscillator's cross patching possibilities and this allows you to focus more on the sound. While it is a somewhat limited palette of sounds, it offers up a nice range of classic timbres that makes it easy to reach for and lovely to listen to.
14 HP +12v 80mA -12v 80mA
Price: $355