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Mod Squad: Qu-Bit Electronix Nebulae

May 28, 2014

The Nebulae can run Csound instruments, or play and process custom audio files using its granular features.
Put some granular processing and Csound in your Eurorack

Nowhere else has hacker culture collided with the mainstream more successfully than in the area of Eurorack modular gear. The most interesting hybrids, born from unusual circuit-bending and coding schemes, spread quickly, often leading a designer toward entrepreneurship: And, thus, a module company such as Qu-Bit is born.

One of the most versatile DSP-based modules available is the Qu-Bit Nebulae ($429), which hosts a Raspberry Pi microcomputer programmed to play audio files, offer granular processing, and run Csound instruments. The well-designed user interface makes it easy to load data, and the module can hold up to 9.5 minutes of mono audio, which you can deconstruct in a variety of ways—time, pitch, and other playback parameters are under full voltage and MIDI control.

The Nebulae uses an 11-bit DAC running at a sampling rate of 22.05kHz. It supports stereo or mono WAV, AIFF, Flac, and Ogg files, though it plays everything back in mono. (Qu-Bit also recommends you use mono files because they load quicker.)

Loading files is easy: Power up the module, plug in your USB stick, and the system automatically loads the sounds or .csd file stored in the drive’s root directory. (.csd files get priority if they share the root directory with audio files.) You can unplug the USB drive when using Csound and in Looping mode, but you must leave it in for One Shot mode.

To load something new, insert the USB drive that has what you want on the root level, then hit the Edit and Next File buttons together. Load time is surprisingly quick. When powered down, the module’s SDRAM dumps whatever you’ve loaded into it, though you can save presets of the current CV and knob states to a USB stick. You will want to have USB drives dedicated to each sound set or .csd file you plan to work with.

The module comes with a thumb drive containing sound files, documentation, and five Csound instruments—a synth voice with FM, a Karplus-Strong plucked algorithm (with 10-voice polyphony), an oscillator that plays seventh chords, another with four tunable waveforms, a vowel-formant instrument, and a .csd template for rolling your own. The Qu-Bit website also provides the Nebulae’s source code (including Arduino .ino files) and schematics for you DIY types.

In addition to the Looping and One Shot performance modes for audio-file playback, there is a systemediting mode. The front panel indications are for Looping mode, where a selected sound file continuously repeats. The panel I/O and controls are mapped differently for the other modes and Csound instruments: Qu-Bit provides documentation for each layout.

In Looping mode, you can use CVs to step through the bank of sound files in either direction or randomly; freeze playback; alter the rate, size, and wet/dry mix of the grains; and change the loop size and starting point in real time. Knobs for each parameter adjust the CV response, and you can have consistent distance between grains or variable distances (Scatter). The Drive control provides analog distortion on the output.

In One Shot mode, you can play up to eight individual audio files using discrete analog gate inputs, front-panel buttons, or MIDI. A knob controlling playback speed is available for each file, as well as a global varispeed control. Drive is also available on the output. This mode is great for creating a simple, sample-based drum machine with your Nebulae.

Although granulizing my own sound files was fun, I enjoyed the powerful instruments made possible by the implementation of Csound. Because the module is based around an open-source framework, you can expect a library of user-designed instruments to develop over time, which will allow the Nebulae to stretch your modular system far beyond what you ever thought possible.

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