Review: Soulsby Synthesizers Oscitron

The Oscitron from Soulsby Synthesizers is a lot of things. It’s their first Eurorack synthesizer product. It’s an 8-bit digital oscillator with wavetable sampling, selectable audio engine resolution, multiple filter types, scale quantization, portamento, bit reduction and preset memory. Amazingly, they managed to squeeze all this functionality into just 14HP. This is achieved through the clever use of two knobs that also function as buttons.

You Know I Got Soulsby

The top function knob has two menu rings, and pressing it toggles between the red and green menu sets. This selects the page of parameters that the bottom button will edit. Additionally the Oscitron has knobs to control fine tuning, pulse width, filter frequency, filter resonance, and phaser offset. It provides 1v/Octave CV inputs for pitch and filter cutoff frequency, as well as inputs for pulse width, filter resonance and phaser position. There is also a clock and audio input for sampling new waveforms.

I was pleased when I opened the box to see both a detailed manual, a quick reference card, plus a cute pair of mini wood cheeks. I really appreciate it when manufacturers make this kind of extra effort. I generally prefer hands-on manuals to PDFs and I’m a sucker for wood cheeks on synths. Another unexpected discovery in the box was a little 2HP module called the Uni-Five with its own reference card. I reached out to Paul Soulsby to ask him about the Uni-Five and he was happy to give me a thorough explanation.

Paul explains : “the reason for the Uni-Five module is partly because the Oscitron is digital and partly to do with Eurorack theory! Like the Atmegatron, it’s 8-bit digital and only recognises voltages between 0V – 5V. In fact, voltages outside of this range would cause damage, but luckily it has loads of protection against this. If anything is connected out of that range it’ll just clip it to either 5V or 0V.  There’s two approaches to deal with this in the Eurorack world, where anything between -10V and +10V is fair game. I can have on-board attenuation, but the issues with that are: What kind of attenuation do I provide? Bias, attenuation, both, and over what voltage range? Or I can say: better to handle all bias and attenuation myself, so I can customize it for my own system.”

He continues: “when I developed the module, I felt that user customization was more appropriate. However, when I got to beta testing, users kept wanting to put a bipolar LFO into the filter, to make it go wah-wah-wah(!) and found the negative part of the LFO cropped off. I decided it should have some biasing and attenuation for the most common situations (5V LFO and 8V envelope). So I had the option to redevelop the entire product (which would have increased the HP and would have needed all parts prototyped again), or create a separate module, which would be much quicker, cheaper, and simpler, and could also be used with other 5V modules. So that’s basically the option I went with!”

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