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.

Synthesis

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.

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.

Outputs & Effects

Each voice can be routed to any of the four outputs or a digital effects processor. The audio outputs can be used in stereo pairs, mono, or a combination if required. If configured in stereo, each voice has a panner that can be manually set or automated using LFOs, velocity or sequencer automation.

There are four digital effects too: Drive, Ring Modulator, Compressor and Delay, although only one can be active. Any voice sent to the effects bus will be processed then sent to an output of your choice.

Drive offers three different algorithms: tube, wave‑folding and clipping, all with adjustable drive strength, wet/dry ratio, tone, and make‑up volume. The Ring Modulator offers robot beatboxing by multiplying the input signal with an oscillator capable of various waveforms and an adjustable frequency. The Compressor provides simple compression with ratio, threshold, attack, decay, and make‑up gain.

The Delay effect, I suspect, will be the most used. Mono and stereo ping‑pong modes are available, and the delay times are set in two ranges: Low for modulation effects like chorus and flanger (1ms to 20ms) or High for more traditional delays (20ms to 0.7s).

I particularly enjoyed the Drive and Delay effects — the only pity being they can’t be used together. The Clip mode on the Drive effect can introduce delicious feedback that interacts with the input signal in lovely ways. And the Delay effect has a very analogue sound, especially when the delay time is automated using LFOs or sequencing.

Sequencing

The LXR‑02 has everything you need to make sophisticated sequences. Each project can contain 64 patterns and 64 songs. Each pattern can have up to 64 steps and its own kit (optionally loaded when switching patterns).

Every pattern step can contain pitch information, velocity, trigger probability, a flam multiplier, time shift and two automation values. The automation values can be any parameter from the synthesis algorithm of any voice. You can program these individually (if you want different parameters for each step) or record tweaks as the sequencer plays.

Every voice track within a pattern can have a different length. And for quick inspiration, there’s a Euclidean pattern generator. Just enter the length, number of steps and rotations value, and the pattern will be auto‑generated for the current voice. You can even use the pattern generator in a live context, reverting to the saved pattern whenever things stray too far.

The LXR‑02 can transmit MIDI so that you can layer up other sounds from an external sound module. There are no dedicated sequencer lanes for this, so you have to use one of the voice lanes. The LXR‑02 will also send program changes when you change patterns (and respond to them if required). All of this is optional, of course. You can turn off transmission of MIDI notes, control changes, program changes and clock individually in the settings.

In terms of sync, there are MIDI and analogue clock options, and the LXR‑02 can act as clock source or destination. The resolution of the analogue clock is adjustable, so it should work with just about any configuration.

Song mode allows you to build a playlist of patterns. It’s a simple list. You can insert more patterns anywhere in the list, and there are a couple of ‘special’ pattern types: End, for the end of the song, and Loop, to loop back to the beginning. I cannot imagine anyone seriously writing a song with it, but combining a few patterns into a longer chain is a valuable function.

External Control

For those who prefer to sequence externally, the LXR‑02 has a comprehensive MIDI implementation. Each voice could have a MIDI note on MIDI channel 10. Or, if you choose, each voice can have a separate MIDI channel that can play chromatically. For those who want to use an external MIDI keyboard to program the LXR‑02’s internal sequencer, you can set up a global MIDI channel to control whichever voice is currently selected.

A detailed MIDI CC chart offers external control over almost every synthesis parameter. MIDI CCs are received on the global MIDI channel, which does present a problem if you want to sequence externally because you have to send your note triggers and MIDI CCs on different channels.

The LXR‑02 can also route MIDI between its USB and MIDI DIN ports, turning any port output port into a thru port. For example, you can route USB input to MIDI DIN output. Or MIDI DIN input to MIDI DIN output. Or even merge both the USB and MIDI DIN inputs and pass them to the MIDI DIN out. This flexibility is a nice touch that allows you to fit the LXR‑02 into just about any setup.

I haven’t been this excited by a drum machine for years, and I can’t recommend the LXR‑02 enough.

Conclusion

I like the LXR‑02 a lot. Its physical size hides a monster drum machine capable of tearing your productions a metaphorical new one — if you’ll pardon the expression. As a purely digital device, it manages to avoid the analogue clichés that are so common whilst still managing to sound full and fat.

FM synthesis, in particular, is brilliantly suited to electronic percussion generation. The synthesis algorithms are complex enough to offer a broad palette of sounds, but the LXR‑02 still has a unique signature. It’s a ‘highly electronic’ sound, by which I mean that you won’t be synthesizing any realistic drum sounds here. Overall, the sounds are dynamic and transient. It’s crisp and clear when you want it to be, or filthy and muddy and swimming in feedback. I’d recommend the LXR‑02 to any electronic musician who embraces pure synthesis. There are no samples to hide behind, but it simply doesn’t need them.

The internal sequencer is impressively feature‑packed. Probability, flams, different track lengths, automation per step — these are things you might not expect to find on a machine of this size and price point. Having four outputs configurable in any way is also fantastic. There are drum machines at twice the price with only a single pair of outputs (shame on them!). The MIDI implementation is equally impressive, with USB, MIDI DIN and enough config options to satisfy almost any situation.

Of course, nothing is perfect. The compact front panel squeezes a lot of buttons into a small space, and I found myself pressing the wrong button too often. The larger round buttons also have a clacky feel, which I wasn’t fond of. But, these minor imperfections don’t matter. I haven’t been this excited by a drum machine for years, and I can’t recommend the LXR‑02 enough. 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!