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LEP LepLoop

Analogue Groovebox
By Paul Nagle

LEP LepLoop

The LEP LepLoop takes a decidedly unconventional approach to the groovebox format.

The LepLoop is an analogue synth, sequencer and percussion module all the way from sunny Italy. Hand-built into a light wooden enclosure, this tiny groovebox is pock-marked with patch points and able to hook up with MIDI, CV or DIN Sync gear. Regardless of its connectivity, the LepLoop inhabits a wayward world of its own when it comes to traditions such as melody and control. This is because at its heart is a sample and hold generator that provides source material for a looping analogue sequencer. Notes generated at random are captured and — if you like what you hear — worked on until you feel like dipping in again.

Inside are two VCOs, a noise source, a low-pass filter, a dedicated bass drum, twin VCAs (each with a simple envelope) and a switching system offering near-modular flexibility. With a four-track digital trigger sequencer lending rhythmic support, will 2016 prove to be a LEP year?

Lep Into The Unknown

Fitting perfectly on my A5-sized diary, the LepLoop has a busy panel littered with switches, buttons, knobs and mini-jacks. While the feel of real wood is always welcome, the buttons are rather small for lengthy prodding pleasures and the knobs don’t exactly scream ‘quality’ either. To further dampen first impressions, the four panel screws are much too large and are positioned poorly — one of them physically impedes the VCO1 frequency control and another completely overshadows the piddly ‘SH2’ button. Considering this is a hand-made device, it’s not unreasonable to think these issues could have been ironed out in the early days. Unfortunately the quality concerns continued when, later, one of the many plastic switches failed.

Supplementing the panel’s patch points, additional connections are tucked away in the recessed rear. Actually, although the four rubber feet suggest ‘knobs-skyward’ as the optimum working position, Eurorack users might prefer to stand the LepLoop with its sockets facing upwards instead. This would give better access to the nine mini-jack outputs (carrying audio and CV/Gate), plus the full-sized jacks that deliver the mix and bass drum signals. Amongst the smaller audio connections, one is a copy of the mix (which you could use as a headphone output if necessary) while the other is the raw output of VCO2 — ideal as a modulation source when patched back into the CV input of a VCO or VCF.

As well as plentiful CV/Gate connections, a MIDI In socket is present for MIDI sync and control. It’s possible to drive DIN Sync gear too and transmit both DIN and MIDI Clock, even though there’s no external sign of this. The wiring information and details for making the necessary custom cables are available from LEP if you’re so inclined. Power is supplied by a 12V AC wall-wart.

Turning on, I almost panicked at the burst of noise and activity. LEDs flashed in many colours and an assortment of freaky sounds rushed out like hyenas escaping captivity. Only then did I look (in vain) for transport controls, but the LepLoop laughs at such conventions. In desperation I pulled the plug and began to scrutinise the manual, but it’s not an easy read when you’re searching for quick answers. However, it does prepare you for what’s to come: lots of holding down buttons, toggling LED colours and checking the status of switches. LEDs are an integral part of this screenless analogue groovebox so I was grateful for the matrix of text listing the functions of the shift buttons (SH1 and SH2) in each menu (as shown by an LED that’s either off, red, green or yellow).

Panic Over

Fortunately, starting and stopping wasn’t terribly complicated after all. Indeed, if you switch the clock source to ‘Ext’, the LepLoop becomes a willing MIDI slave. If you don’t connect a MIDI lead, this setting works slightly differently: the SH1 button becomes tap tempo, responsive to the last pair of taps. Should you wish to stop playback, wait five seconds then hit the button once. Intuitive it is not.

When using the ‘Int’ setting, you’ll need to take care not to accidentally touch the bpm knob. The LFO waveform selector switch is pretty close by so it’s easily done, but this proved to be a minor issue compared to the more obvious one, which was: where or how do I get started?

The use of switches creates many routes for sound to percolate through to the outside world and it’s only with patient examination that it starts to click. In panic situations, the mixer is your friend and its first entry is conceptually the simplest — Cassa, the analogue bass drum. I should point out that use of its dedicated output does not remove Cassa from the main mix. If you plan to get the most out of the bass drum by processing it separately, you should ensure its mix output is zero.

There are 16 banks of 10 patterns ready to be filled, and rather than try to understand those already present, one tip I’d have appreciated at the outset involves the ‘reset track’ option. Two quick presses of the Menu button lands you in the Green menu; from there, holding both SH1 and SH2 clears all the note triggers so you can start from scratch. As the LepLoop is live and interactive, you needn’t stop the music to perform any track tweaking or even to load in new patterns.

The LepLoop’s rear panel contains a  host of CV, Gate and Clock outputs on 3.5mm sockets, a MIDI input and quarter-inch outputs for the Cassa (kick drum) and synth. The LepLoop’s rear panel contains a host of CV, Gate and Clock outputs on 3.5mm sockets, a MIDI input and quarter-inch outputs for the Cassa (kick drum) and synth.

Mi Cassa

For the easiest introduction, I elected to begin with Cassa, so named as another reminder that the LepLoop is proudly different. Google suggests ‘cash’ as the translation, possibly in a sign of confidence, because Cassa is a fine-sounding analogue bass drum. Even so, its controls don’t always behave as their labels imply. Take frequency, for example; at low resonance it barely changes the pitch of the bass drum at all, except in the last few degrees of the knob’s travel. Instead, it makes subtle tonal changes. Once resonance is involved, it behaves very differently. Resonance contributes a mad, ringing presence, and at its highest values the bass drum turns into a continuous drone. Or, when the frequency is low, it becomes a bizarre and ominous didgeridoo. With no decay control, resonance is the only way of significantly extending the envelope and adding more body to the kick.

Distortion is a rough and ready overdrive, except when frequency and resonance are both high when it performs a neat impression of a nasal filter sweep. Those three knobs offer a lot of variety even before you start to apply external processing. The final control, Accent, blends the pulses generated by Cassa’s dedicated trigger track and the track that drives the sample and hold process. Depending on the activity of either, it can be used to add fills or thin out a busy pattern. When Accent is turned fully clockwise, the bass drum is triggered entirely from the S&H track. That almost wraps it up for the bass drum, except to say that it can be sent through the 24dB filter if necessary, although at the expense of the synth sources.


Before checking out the synthesizer, it’s worth gaining an appreciation of the unusual sequencer that triggers it. Or sequencers, rather, for there are five in total. The analogue sequencer isn’t as easily spotted as the four digital tracks — Cassa, S&H, Env1 and Env2 — whose triggering is obvious due to flashing LEDs in green, red, yellow and blue. The digital tracks are purely for triggers: there’s no memory of the panel’s knobs and switches, they’re always live.

Programming triggers involves a trip into the Green menu where the SH1 and SH2 buttons are employed to enter notes and rests in step-time. Initially, it’s not always clear which track is selected, until you get used to matching the flashes to the steps marked active in the row of 16 smaller LEDs. A digital track may be up to 64 steps long but can be freely divided into four tracks of 16 steps, or even 8x8 subtracks. In other sequencers, these divisions would probably be referred to as bars. Anyway, you’re given plenty of options to make variations and switch between them in performance. More importantly, the LepLoop can be a rich source of complex polyrhythms. Not only can you specify individual lengths for the four trigger tracks, but each can run at its own clock division. Nor are you constricted to progressing through the track one step at a time.

To experience such rhythmic delights, you’ll need to enter the Yellow menu, accomplished by holding the Menu button for more than three seconds. Here, you can move the play position relative to other tracks or push the track in single clock increments — groovetastic! Further key combinations change the way steps advance, and the LepLoop can serve up everything from double-sized jumps to backwards movement or movements that defy easy description. You can also stop tracks — and without an obvious means to mute them, that comes in pretty handy.

Such flexibility can result in tracks getting out of sync. While this can be desirable, I was impressed that the LepLoop’s engineers had anticipated the need to realign them. With a single button press all the positions can be reset when necessary.

The analogue sequencer takes a completely different approach. It has a maximum of 16 steps and each step stores its value in a capacitor — analogue memory that discharges over time. The sequencer is fed from the output of the sample and hold process and for every trigger of the S&H track, a value is grabbed and stored. This keeps happening as long as the Rec function is active. Flip the switch from Rec to Loop and the recording ends, leaving a looping pattern you’d probably never have produced manually. Its output is available to the two VCOs and the filter cutoff frequency.

In many ‘normal’ synths, S&H is simply a randomness generator placed for convenience amongst the waveforms of an LFO. Here, it’s an entirely different entity with a choice of two sources for the S&H process. Depending on the selection, you get a very different flavour of generated sequence. When white noise is the source, the values will indeed be random but if the LFO is chosen instead, S&H will emit rising, falling or alternating values depending on the LFO speed and waveform.

The analogue sequencer also has four running modes, including ‘being advanced and reset by other tracks’. Impressive and often mind-bending, it can even create melodies where the notes are of different lengths. The sequence can be edited (in a fairly laborious fashion) by shifting the notes of each step up or down, but I realised quite soon that precision bass lines and well-tempered scales aren’t the LepLoop’s forté. You can achieve properly-pitched melodies, though, and we’ll look at how after a short interlude spent with the synth.

The Synth

There aren’t many twin VCO synths that pack so many modulation options into so little space. The first oscillator offers a choice of square or triangle waves; the second, only sawtooth. Their frequencies may be modulated by sources such as the two envelopes, an inverted envelope, the analogue sequencer, S&H and LFO. Each oscillator is fitted with a single frequency control that sweeps the pitch from LFO rates up into tinnitus levels. It’s not exactly precise, but then precision would be out of character anyway. The mixer consists of a single knob that sets the balance between the VCOs and there’s a ring modulator too for yet more sonic madness and bell-like excesses.

VCO2 has a bit extra in the form of frequency modulation, with sources of VCO1, Env1 and the LFO. Already, that’s practically the whole story, but due to the matrix-like switching, the oscillators are much more versatile than you’d think. They deliver atonal cross-modulation, percussive clanks, substantial bass, cheesy vibrato and almost limitless wibbly nonsense.

Either the VCO mix, white noise or the bass drum can be processed by the filter; a 24dB analogue design with a wide range and a resonant wail like a wounded cat. It sounds pretty good and its raw output is available at the mixer for whenever drones or general insanity is required. The cutoff and resonance can be modulated separately and given that there are independent trigger tracks for each envelope, it’s a fairly simple matter to draft in the self-oscillating resonance as a source of extra percussion.

The LepLoop is more compact than it may appear in the photo, its front panel measuring just 206 x 154mm.The LepLoop is more compact than it may appear in the photo, its front panel measuring just 206 x 154mm.

The LFO’s waveforms are sine, triangle and square and, unusually, there’s an offset control that shifts the entire output up or down. The practical benefits of this are felt when populating the analogue sequencer using the LFO as the S&H source; the offset determines the range of pitches recorded.

The VCAs each have a two-stage envelope, and you won’t be surprised to learn that switches control their source. VCA1 has a three-way choice of noise or either VCO, plus there’s a choice of modulation source — either the LFO, Env1 or S&H. The second VCA is hard-wired to Env2, its input either the VCF or VCO1. If this sounds like a lot to take in, it is — but there’s more. Until now I’ve deliberately kept all those patch points out of the picture, but naturally they add a heap of extra routing possibilities, some of which inevitably depend on switches!


While the on-board sources are flexible enough, more sonic sculpting can be achieved by drafting in external voltage sources. Both oscillators and the filter cutoff are addressable, although I had a little trouble at first, partly because I failed to read the manual thoroughly and partly because of a faulty switch. In the case of the latter, it locked out external control of VCO2 unless I was physically touching it.

The oscillators track well. At least they do when you spot the phrase ‘linear CV response’ and realise you must drive them with a Hz/Volt source. Considering that all I’d produced until that moment were tuneless riffs and random ring-modulated bass lines, it was a pleasant surprise to hear regular melodies. It turns out the LepLoop has an in-your-face acidic charm when its pitch is handled by a normal sequencer — who’d have thought!

External processing of signals via the filter is another easy win, and the raw filter output is always accessible; you don’t even need to worry about triggering an envelope or starting the sequencer to hear it, although if you do, you can treat your signal to envelope shaping at the flick of a switch.

For modular synth owners, those CV and trigger signals are welcome bonuses. Who doesn’t have a use for an extra couple of envelopes, a dash of sample and hold, another LFO and 16 steps of a sequencer? Ditto for the extra gate sources, of which the LepLoop’s impressive list includes the trigger output from the S&H, sequencer and Cassa, plus a regular clock out too.

MIDI brings a number of handy extras to the table over and above synchronisation. Two MIDI channels are required: one for the digital tracks and the other for the analogue sequencer. Using MIDI you can play melodies and the bass drum, trigger envelopes, advance sequencers and more. The manual contains a trigger map showing the MIDI notes and their actions, and you’ll probably need it for a while, because there’s a lot involved. It’s worth the effort though, especially if you fancy giving the LepLoop a more controlled and structured role.


It’s hard to believe I’ve got this far without resorting to ‘quirky’, because that has to be the perfect one word summary. It took some time before comprehension dawned, but once I embraced the chaos, the LepLoop started to make some kind of sense. Sonically there are many pluses: the filter sounds sweet enough and although the oscillators are simple, their wide range and scope for modulation ensures a rich palette of tones. If all else fails, there’s always that fab bass drum to fall back on as a solid backbone for the drones, atonal sequences, noise hits and random electronic textures.

At the price I didn’t expect luxury, but the standard of construction wasn’t great. Even if we accept that the LepLoop has to be as small as it is, it’s hard not to be disappointed with the quality of the knobs and switches — not to mention those unsightly screws! The menu system isn’t the most intuitive either. However, if you can get over these shortcomings, there are rewards to be had. Those S&H-sourced sequences are here today, different later, forgotten tomorrow, and it’s this that gives the LepLoop its unique character. It doesn’t have to be unremitting ephemeral wackiness either. When harnessed under CV or MIDI control, some level of normality is achievable.

Oddly enough, even with the polyrhythmic delights offered, I didn’t make much of a dent in the large pattern pool, perhaps because every pattern changed the moment I started fiddling with the knobs and switches. This, it seems to me, is really the point. To get the best out of the LepLoop means using it in a constantly-changing, unrepeatable performance. As an antidote to tame, predictable gear or just as a source of ‘unique, grab while you can’ loops, there’s nothing else quite like it.


I can’t think of any other machine that takes you beyond normality so quickly. You might consider marrying a Korg Monotribe or Volca to a Roland Boutique synth such as the JP08. While these would never be a complete match for the LepLoop’s unruly and baffling nature, at least you’d have change left over for an effects box or therapy.


  • An analogue groovebox and weird-noise generator extraordinaire.
  • Takes a novel approach to sequencing.
  • Includes a versatile bass drum complete with separate audio output.
  • Generous CV interfacing.
  • MIDI sync and control.


  • Some quality issues.
  • It’s more than a little obtuse.
  • Requires dogged patience and a taste for happy accidents.


A tough one to summarise, LepLoop is like a wayward child capable of great brilliance or snarling insolence. While it could be a culture shock to anyone weaned on mainstream grooveboxes and drum machines, alternatively it could be a breath of fresh air.


€649 including VAT.

SchneidersLaden +49 (0)30 9789 4131

Published September 2016