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Sonic Potions/Erica Synths LXR-02

Drum Machine By Rory Dow
Published April 2022

Sonic Potions/Erica Synths LXR-02

Sonic Potions and Erica Synths team up to create a truly unique drum machine.

The Sonic Potions LXR was an affordable DIY project released back in 2014. For those with the requisite soldering skills, it offered a six‑voice FM/subtractive sound engine with a sequencer, four different synth algorithms, MIDI, and open‑source code. Sonic Potions sold the component kit to build the machine and a separate acrylic enclosure. Erica Synths subsequently offered an all‑metal enclosure.

Not everyone has the time or inclination to solder their instruments, so Erica Synths and Sonic Potions have teamed up to create the LXR‑02. It is not available as a DIY kit, and the operating system isn’t open‑source, but otherwise the LXR‑02 doesn’t stray far from the original concept. It’s a six‑voice digital synthesis drum machine with an onboard sequencer. There’s plenty of tweaks and improvements, of course, the addition of volume faders for each voice being the most obvious. Overall the general design philosophy seems to be one of accessible tweakability. Rarely is anything more than a click or two away, and you can edit everything without stopping the sequencer.


The LXR‑02 uses a combination of subtractive and FM synthesis. There are four main algorithms: Drum, Snare, Cymbal/Clap and Hihats. The synthesis parameter pages are cleverly grouped so that no matter which type of sound you are editing, you can hit a button and go to the relevant page for that algorithm. No matter whether you’re editing a snare or a hi‑hat, if you hit the Filter button, you always go to the filter page for that algorithm.

The first three channels use the Drum algorithm, a mix of simple FM and subtractive synthesis. The primary use is probably kicks and basses, but they can easily make toms, percussion, snares, laser zaps, etc. The Snare channel is more focused and uses subtractive oscillators and noise to create snares and percussive hits. The Cymbal and Hihats channels use a more complex FM setup to create metallic, enharmonic sounds. The Open and Closed Hihat channels use the same synthesis parameters except that each can set a different amplitude decay time. They can then be sequenced separately but will choke each other.

Mostly, the synthesis modules used in each drum algorithm are similar. The oscillators create classic analogue waveforms: sine, triangle, sawtooth, rectangle (aka square), noise and PWM. The filters are a 2‑pole state‑variable design with low‑pass, high‑pass, band‑pass, unity gain band‑pass, notch, and peak filter types.

The envelopes are a simple AD design but offer variable exponential and logarithmic curve controls and a repeat parameter that causes rapid retriggering — useful for synthesizing clap sounds. The Drum and Snare algorithms offer two envelopes, one for amplitude and one for pitch modulation. The pitch envelope can also automate a long list of destinations with optional velocity sensitivity. The Cymbal algorithms offer only one amplitude envelope but still provide velocity modulation over many possible destinations.

All algorithms offer a Click page where you can alter the transient using either an additional short pitch envelope, adjusting the starting phase of the main oscillator or mixing in a transient sample. The samples are baked into the firmware and cannot be replaced but offer variants such as acoustic kick, rim‑shot, hi‑hat, clap, tom and finger snap. The samples are short but valuable for adding a consistent transient to any sound.

Each voice has an LFO, which can free‑run or sync to an internal or external clock. It can only control one parameter, but that can be any parameter (including effects) on any voice. Effectively then, you have six freely assignable, global LFOs. Possibly my favourite detail is that you can assign any voice to reset the phase of the LFO. It means you could have a kick drum retriggering the LFO on a percussion track which is controlling some wild modulation. This interaction between sequencer tracks makes for some exciting and dynamic patterns.

A big part of the LXR‑02 sound is overdrive. Both the filter and the output can be overdriven for each drum voice, resulting in sounds ranging from clean and polite to downright filthy. If that still sounds too pleasant, you can add some bit‑depth reduction, which will cause anything from a touch of aliasing to total annihilation. Bit‑depth reduction is also available on the master mix outputs. In all, there is a ridiculous number of ways to roughen up the sound.

If you make any genre of music that benefits from synthesized drum sounds — whether it be techno, electro, electronica, ambient, or a billion others I’ve yet to discover — then you should give the LXR‑02 some thorough consideration. It’s a beast!

Voice & Performace Modes

The LXR‑02 works in two modes: Voice or Performance. Voice mode is where you do synthesis and sequencer programming. Performance mode is for live tweaking.

Voice mode focuses on one voice at a time. Choose the voice using the buttons underneath the sliders, then pick a synthesis page group such as Osc, FM or Filter. The screen will show up to four parameters which can be altered using the four endless encoders underneath. If more than four parameters are needed, the data encoder can access more pages.

Because the screen is relatively small, the parameters have short three‑letter codes. COA is coarse tune, FRQ is filter frequency, DEC is envelope decay, etc. Most of these are easy to figure out, but if you find yourself scratching your head, a quick press of the data encoder will toggle to a single parameter screen, where the full title is displayed.

The 16 buttons will show the sequencer pattern for the current voice. If the pattern is longer than 16 steps (up to 64), you can move between pages of 16 steps using the Bar forward and backward buttons.

The LXR‑02 measures 230 x 145 x 70mm and weighs in at a mere 810g.The LXR‑02 measures 230 x 145 x 70mm and weighs in at a mere 810g.

This method of keeping everything tied to the selected voice is intuitive and easy to grasp. My one gripe here is that the busy layout of the buttons makes muscle memory challenging to develop. You have to look carefully at the panel legends before pressing a button. Luckily, the white‑on‑black colour scheme is easy to read, and the button LEDs aren’t so bright they’ll blind you, even in a dark room.

Performance mode is for live jamming. The Voice buttons below the sliders become mute buttons. The first seven pattern programming buttons become trigger rolls, allowing you to play quantised rolls, at various rates, over the playing pattern. Other global effects such as sample‑rate reduction, pattern‑shuffle, and sequencer tempo are all accessible in this mode. You can still access individual voice parameters in this mode, so tweaking sounds on the fly is still achievable.

Perhaps the most enticing Performance mode feature is Morphing. Every pattern can load a second kit, and morphing will smoothly transform every parameter of every voice from the pattern kit to the morph kit with just a single knob. The possibilities here are mind‑blowing. You can load two completely different kits and enjoy the radical chaos of blending between them, or save a copy of the current kit with subtle changes and use it to tweak a few different sounds at once.

Live editing of a pattern and its sounds might feel dangerous in a live setting, but the LXR‑02 has a handy trick up its sleeve. You can hit the Reload button at any point, and the saved kit and pattern will reload from the current project. So you can deviate from any sound or pattern safe in the knowledge that you can return to a known state.