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Qu-Bit Aurora

Eurorack Module By William Stokes
Published November 2022

In many ways, the discovery of a truly new sound — a reality‑shifting sonic experience — is the never‑ending goal of modular. It’s this very drive that constitutes the heart of Qu‑Bit’s Aurora. “Reverb,” says the developer of the module. “Well... kind of.”

Qu-Bit Aurora Eurorack module.I could leave this review there, with a ‘buy it, throw some CV at it and see what happens,’ since it’s as good a summary of this extraordinary module as you’ll find. The Aurora resides in a netherworld somewhere between pitch‑shifting, reverb and sample manipulation. A ‘spectral reverb,’ it operates with a Fast Fourier Transform phase vocoder audio engine at its heart, reconstructing complex sounds with sine waves and therefore able to delineate between an input signal’s time and pitch properties. This also involves a variable resolution balance between the two: larger FFT sizes will respond to frequency more accurately, while smaller sizes will produce better transient responses. From pitched‑down warbles to glassy swirls, the Aurora can more or less take anything you throw at it and turn it into something, well, else.

The Aurora’s controls, from top to bottom, are for Warp, Time, Blur, Reflect, Mix and Atmosphere. On the left of the panel are buttons for Reverse and Freeze, while a rather elegant colour LED strip flows upward from the onboard USB drive, around the top and down the right‑hand side of the module. Its colours are not only very pretty — in fact, this is among the prettiest modules I’ve come across in Eurorack — they do actually serve a purpose, indicating the status of various parameters. Stereo inputs are on the bottom left, with stereo outs on the right. CV inputs are present for all parameters, including those expecting gate signals for the Reverse and Freeze functions, which is a nice touch. A Shift button is also included for a few under‑the‑hood functions.

Warp is essentially a pitch‑shifting control, reaching an impressive three octaves in each direction and trackable at 1 Volt per octave. This means you could feed the Aurora the simplest oscillation, and with a sequencer patched into the Warp input create an entirely new melodic part with its own tone control and spatial character. Clever. Time, as you can probably guess, concerns the amplitude component of your signal, acting as closely to a conventional reverb decay control as you’ll find here. Blur, on the other hand, concerns the frequency component, smearing and stretching the frequency content of a signal so that things start to bleed into each other in a distinctly digital way. Reflect is a kind of delay control, controlling a strange combination of delay time and feedback. Higher levels will create long, stuttering tails. Atmosphere is akin to a filtering control, with anything below 12 o’clock favouring lower frequencies, and anything above it favouring higher, more airy or glassy frequencies. The Atmosphere control also seemed to bring in an interesting, almost lo‑fi digital sound reminiscent of lossy formats and narrow Internet bandwidths, which was enjoyable to use, if in need of careful tweaking so as not to push the lossy‑ness too far.

There are two takeaways from all of these. The first is that the Aurora doesn’t just take a stimulus and work from its transient, but actually channels the movement of that signal — both in dynamics and frequency — right to the very end of its response. This also means that its response entirely depends on what you feed it — you literally get out of it what you put in. The second is that all these parameters work off one another in a very interdependent way. Turn Blur all the way up, for instance, and you won’t hear a huge amount of character until you also start dialling up the Atmosphere. Reflect and Time similarly work very much as a team, and so on.

The Freeze and Reverse buttons on the left do as you’d expect, with the Freeze holding a sound in stasis to be manipulated as you see fit. Pressing Shift and Reverse changes the FFT size, or the spectral resolution, which should not be underestimated as a tone‑shaping tool, with different resolutions sounding choppier or more washy to various degrees.

I experimented with drums, a single VCO and audio samples of acoustic instruments (flutes, if you want to know). With any of these, at worst I had to work a little to avoid a washy, insta‑ambience that did feel more or less the same regardless of what I put in. At best, I was bringing out characters in various sounds that I didn’t even know were possible.

Modulation is key to the Aurora’s usefulness and character. Particularly with rhythmic sounds...

With a low FFT size, drums could be ornamented with choppy, stuttering artefacts, while at higher settings an oscillator could be shaped into a dynamic, frequency‑rich instrument from another world. Complex audio signals rewarded more careful parameter adjustment, bringing forth ambient chimes of pitched noise or cartoon‑ghostly swells.

Modulation is key to the Aurora’s usefulness and character. Particularly with rhythmic sounds, modulating parameters in various timings would greatly influence its output and open up a new, distinctly musical realm. Apply a syncopated envelope to the Atmosphere input, for example, to control the filtering of a sound over time and add a wholly different layer to its output. Patch long gates to the Warp input to intermittently jump up in pitch and back again.

The USB drive fulfils a key purpose of shuttling firmware updates back and forth from your computer, not least indicated by its placement on the front panel of the module and the inclusion of a bespoke miniature flash drive. Qu‑Bit have already released one (at least, at the time of writing) alternative firmware for the module called Feedback Delay Network reverb, which turns the Aurora into a more conventional, room‑style reverb, complete with control over filtering, pitch modulation and input level, besides the wet/dry mix. It even changes the LED colour to purple and gold, so, assuming there will be alternative colours for different firmware modes, its easy to tell exactly which firmware you’re using as soon as you power on your system. Qu‑Bit are planning more alternative firmware releases as well, “with some currently in development, and many more planned”. Exciting stuff.

The Aurora is a premium boutique effects unit with a price tag to match. For me, though, the price appropriateness of a unit should be assessed according to its longevity, and in the case of the Aurora it’s genuinely hard to imagine it ever not having a use — which I do not say lightly. It can be wild, it can be gentle, it can be grating or it can be beautiful. If those further interchangeable firmwares are as function‑expanding as the FDN reverb, it’ll also doubtless become something like several modules in one, to the degree that perhaps we’ll have to check back in with the Aurora in another review down the line. I’m already looking forward to it.