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Knob Technology SGR1806-20

Eurorack Module By Robin Vincent
Published May 2024

Knob Technology SGR1806-20

Some 50,000 light‑years away is Magnetar, a weird neutron star of immense magnetic density that identifies as a soft gamma repeater. Just over there in my rack is its modular namesake, a weird module of immense signal density that identifies as an analogue drum synthesizer. One can emit gamma rays that disturb the curvature of space‑time, and the other can take CV and bang out beats that will get even the most uptight aliens dancing. Welcome to SGR1806‑20, the Eurorack module.

The SGR1806‑20 (let’s call it SGR for the sake of simplicity) is an analogue drum synth module from Knob Technology. It’s brash, spacey and corrupted, pulling you away from any sense of order into a warped mass of unstable waveforms, strangled noise and torrents of unexplained extraterrestrial communications. It lurches from clicks to grit to getting pulled through gravel and on to the sort of sonic mayhem that sounds like you’re tuning the radio on a dying spaceship. If there’s something stable in here, then I haven’t found it, but that’s probably the point.

The SGR has two sources of sound: a ‘Voice’ block with a clash of three triangle VCOs, and a ‘Noise’ block containing three noise generators. These get mixed, folded and distorted to arrive at a VCA as a space‑time anomaly.

The Voice is built from three unsynchronised triangle waveforms. It’s inspired by the Buchla 259 complex oscillator...

The Voice is built from three unsynchronised triangle waveforms. It’s inspired by the Buchla 259 complex oscillator and there are definitely complicated things going on between these oscillators. There’s a Spread function that detunes oscillators one and three with reference to oscillator two. They go in different directions depending on which way you turn it and at no point will they bring it all back to some lovely resolution, it’s always just a little bit off.

Two other controls force the voice into self‑modulation. FM pushes each oscillator into the next whereas Feedback pipes some of the output into the voltage summing unit of the 1V/oct input. The result is chaotic with occasional moments of clarity. With everything dialled back you can get SG to play a tune, but frankly, it’s not that interested. What it seems to be looking for is explosions of energetic texture, and those are very easy to find.

Noise Engine

The Noise engine is ridiculous. It has a single control that sweeps it from white noise to fax machine, broken radio to system crash.

Lastly, we have a four‑stage wavefolder and distortion. The wavefolder plays with each voice differently. The Voice gets bent, folded and generates harmonics while the Noise gets phase‑shifted and together they “create new spectra at the intersection of filtering and distortion”. I don’t know about that but it’s certainly true that a little bit of folding enlivens the signals. The Distortion rounds off this sonic adventure with a suitable dollop of overload.

As a drone I thought it was like some kind of energetic alien space radio searching for life in the far reaches of the cosmos. However, that’s not what this is about. The protagonist of this story is the Envelope and the rupturing influence provided by the Trigger input.

The envelope is a straightforward percussive decay envelope that ranges from snappy clicks to open infinity. Through the array of yellow buttons, the envelope can be pumped into pretty much everything. It instantly takes any parameter to its peak and then drags it back to Earth. If you consider how the FM engine is feeding oscillators to each other and the Spread is speeding up or slowing down alternate waveforms, or how the fold is disrupting the shape, and the Noise Tone is still searching for Alien Classic FM, then that envelope can do an awful lot of damage.

...with the right combination of triggers, envelope routing and modulation it was a totally magnetic experience.

Feed it some triggers and it starts to spit and revolve, pulsate, crack and squelch its way through rhythms. And as with most percussion synth voices the magic happens when you patch in some modulation. Everything has a CV input so you can flip the mix knob between booming kick drums and frazzled spurts of noise, or tickle the decay from penetrating clicks into zaps and warbles of crashing harmonics.

On the down side I thought the front panel was a bit of a mess, difficult to read and not exactly easy on the eye, but it did light up in interesting ways. It took quite a bit of experimentation to find my way around, and the results were often unexpected and maniacal. One thing I found quite hilarious was that I could be crafting away on an intricate cascade of interesting clicks only to find a universe of extraordinary alien sounds when I opened up the envelope. But with the right combination of triggers, envelope routing and modulation it was a totally magnetic experience.

SGR1806‑20 is capable of conjuring up an endless supply of broken rhythms and angry textures. It’s thoroughly weird and satisfyingly alien.