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Dreadbox Erebus

Analogue Synthesizer
Published August 2015
By Paul Nagle

Dreadbox Erebus

The Dreadbox Erebus is an unusual small–format synth with an inviting price tag.

Unlike Greece’s primordial god of darkness, after which it is named, Dreadbox’s Erebus synthesizer is not born of Chaos but of a chap called John in Athens. Dreadbox began by making boutique pedals, only branching into synths in 2013 with the Murmux Pedalsynth, a fat bass machine for players with nimble feet.

The Erebus has what I later perceived to be a carefully chosen blend of features, not least that it’s probably the most affordable duophonic analogue synth around. Add to this a built–in MIDI-to-CV converter, distinctive filter, echo unit and patchbay, and you can dismiss any fears of Greeks bearing gifts. The low–cost analogue market has never been more alive — so are these attributes enough to separate this attractive desktop synth from its rivals?

Green Box

Before me sits a rugged metal box painted in grey and a shade of green that suggests fluorescence (which, sadly, is not the case). It measures a substantial 225 x 160 x 55 mm, is edged in wood and populated with classic–style knobs of high quality and mixed size. Only a few are packed too close for comfort. Several of the smaller variety are quite weighty — so much so that it was hard to move them quickly at first. However, I’ll take that response over ‘light and easily disturbed’ any day. The largest knobs are reserved for tuning the two VCOs, adjusting the filter cutoff and setting the output level.

On the panel are a number of three–way switches, and the behaviour of those responsible for oscillator waveform selection deserves a mention. These switches have a middle ‘off’ setting — but when you choose it, you don’t get silence. Instead, you are treated to the output of the other oscillator, regardless of the position of the Mix knob. In order to cut out both VCOs, both waveform switches need to be off. (Typically you’d do this when processing external audio.) It’s a peculiarity, but hardly fatal. Overall, the knob and switch count is generous, and when you factor in a CV patchbay positioned so it doesn’t obstruct regular knobbing, the Erebus begins to look and feel like a potent little synth.

Although it’s possible to run exclusively from the CV (1V/Oct) and Gate inputs, the Erebus is probably best operated by MIDI. That way you can make use of the mod-wheel output on the patch panel. Joining the rear–set MIDI In is a MIDI Thru, which wasn’t functional on the review unit.

One operational quirk I experienced right away involves accessing and changing the MIDI channel. Having temporarily misplaced the manual, I was stumped how to do this until I downloaded another copy and discovered that a screwdriver is needed. You probably won’t change channels regularly, as doing so involves unscrewing the four rubber feet and removing the base plate in order to reach three internal DIP switches. The available channels are: 2–7 or all (omni mode). It’s odd, but at least there is a choice. Incoming MIDI notes are accepted over a five-octave range but velocity is ignored.

The audio output is a firmly attached quarter–inch jack. It’s adjacent to a similar socket that serves as an input for any audio you care to pass through the Erebus’s filter and echo unit. There’s no level control but I found the line-level output of a string synth and a drum machine worked fabulously. Power is drawn from a 12V AC adaptor.

Mighty Dread?

Plug in, and there might be no indication you’ve done it. Lacking a power or MIDI status indicator, the only way you’ll know the adaptor isn’t a dud is by observing the red LED that marks the slow–cycling, free–running LFO. If the rate knob is much below the 12 o’clock position this could take a while because, at its slowest, a complete cycle runs to almost two minutes. The LFO has two waveforms (triangle and square) and a range from 0.009Hz up to 30Hz. Lovers of long, lazy filter sweeps are going to relish the Erebus.

Both VCOs sport sawtooth waveforms, with the first given an optional square, the second a triangle. Both have slightly different ranges, the first offering 8’, 16’ and 32’, the second pitched an octave higher. Unusually, each has a separate glide amount, but there’s a single mix control to balance the levels.

The Erebus’s rear panel features a socket for the external 12V power supply, quarter–inch input and output sockets, and MIDI In and Thru sockets.The Erebus’s rear panel features a socket for the external 12V power supply, quarter–inch input and output sockets, and MIDI In and Thru sockets.

The oscillators take a while to stabilise fully; the manual says it should take between five and 20 minutes, but sometimes it was slightly longer, perhaps because my studio is an ice box right now. I’m pleased to report that the oscillators are warm and full–bodied. This is just as well because they aren’t overloaded with features, unless you count the many tuning subtleties afforded by those larger–than–average knobs. The first of these is master tuning, the second an offset for VCO2. I measured the intervals at five semitones up, nine semitones down: a good range for precise control even if an octave either way might have been preferable.

The filter is a characterful two-pole design that is fat, dark and mildly aggressive. I suppose the darkness shouldn’t be wholly unexpected, at least if you have a passing interest in Greek mythology; the attitude is primarily due to a residual resonance that’s present even with the control at minimum. This delivers a richer, thicker tonality than most 12dB/octave filters.

Interestingly for a small, affordable analogue, there are two envelopes, an ADSR and an AR type. The former is aimed at the filter, the latter the output stage. The filter’s ADSR offers single or multiple triggering and incorporates, over the first few degrees of the sustain’s travel, a negative level. The envelope depth doesn’t waste any of its precious travel on negative amounts, a fact that’s appreciated when seeking the perfect shape for sequencing. Further boosting its capabilities in such roles, the filter envelope has a fast, snappy decay. The AR envelope is simple, yet doesn’t feel too much like a compromise. Its maximum release is approximately 10 seconds and ideal for smooth, flowing solos and drones.

Amazingly we’ve already dealt with almost all the synthesis on offer, and it’s time to take a diversion from the usual routes. The Erebus has a built–in delay with dedicated time, feedback and mix controls. In my humble opinion, every analogue synth should have one — even when it’s as ugly as this! Although it’s digital in nature, analogue–style pitch–swoops are created as you adjust the echo time. At high levels of feedback, the overload is what I’d usually describe as ‘nasty’, or if in diplomatic mode, ‘an acquired taste’. Go to maximum feedback and you’re rewarded with dangerous levels of churning self–oscillation.

I’d estimate the maximum delay time to be around 700ms. Upwards from 350–400 ms, distortion creeps in. This quickly becomes too insistent for most conventional musical purposes, but still relevant for sound effects and miscellaneous wackiness. Echo is capable of reverb–tank or spring reverb impersonations and its very shortest times can hint at chorus, especially with a little modulation applied, of which more anon.

Para Trooper

Although the Erebus is billed as a paraphonic synth, the term duophonic is a neater fit, given that it has two oscillators. When you switch to duophonic mode, the lowest incoming note is routed to VCO1, the next lowest to VCO2. These progress to the filter and amp stage together as usual, with the filter envelope’s triggering playing a crucial role in how notes are articulated. Single mode offers the smoother path, while multi mode introduces the increased precision of, say, an ARP Odyssey and retriggers the envelope on each note regardless of any legato.

The twin glide controls come into their own in duophonic mode. A dash of glide on a single oscillator helps differentiate it from the other and partially blurs the effect of the shared filter and amplifier. Unfortunately, most of the glide controls’ rotation lands you firmly in the special effects department: in other words, the values are scaled too high to be generally useful. Dreadbox have acknowledged this and intend to address the issue in future models.

Still on the topic of glide, I should quickly mention that it glide an absolute value rather than being proportional to the distance between keys. It’s therefore less subtle than it could have been. A more important issue, though, is the lack of auto-glide. This is a fat and bass–heavy synth steeped in squelch potential and it’s therefore a real pity that you’re unable to invoke glide by playing legato.

VCO2’s pitch can be isolated by holding two notes then switching to unison mode. This has the effect of tying the oscillator to its current note until you swap back and free it again. Using the generally higher–pitched second oscillator in this way adds an interesting flavour to drones but it’s one I came to enjoy.

As I played duophonically, I discovered a design benefit I’d hitherto overlooked. Having pondered whether a second square wave would have been of more value than the triangle, I realised that by selecting the purer waveform, you’re able to give a better hint at two discrete voices since the reduced harmonic content is less dramatically affected by filter sweeps.

The Erebus crams a lot into its 225 x 160 mm front panel.The Erebus crams a lot into its 225 x 160 mm front panel.

The Ins & Outs

To get the most from the Erebus you need to master patching. Ignore it and the LFO becomes nothing more than a flashing LED, since it has no hard–wired connections. The mini–jack patchbay is divided neatly into nine inputs and six outputs. It features a pair of ‘mini–knobs’ that provide attenuation of the Mod and Env outputs. Without these, patching would always be limited to the full range of the modulator, unless you resorted to an external mixer of some kind. Mod refers to the modulation-wheel data extracted from MIDI.

The outputs are as follows: Mod, Gate, Env, CV1, CV2 and LFO. Most are self–explanatory but perhaps CV1 and CV2 are not. These are the note values used for duophony as chosen by the internal MIDI-to-CV converter. You could therefore use them in conjunction with other synths, should you prefer to avoid the sharing of envelopes and filter. Put the Erebus in unison mode and the two CV outputs are identical.

The inputs are more numerous: VCO1 frequency, VCO2 frequency, CV (both oscillators), VCF, Echo Time, Gate, LFO Rate, LFO Depth and Resonance. It’s a healthy list, even if three oscillator frequency inputs could be viewed as excessive in the light of PWM’s absence. However, it means you’re given the rare opportunity to apply modulation to each VCO individually. Super–rich vibrato can be yours for the cost of an external LFO.

Some of the other inputs are just as uncommon. It’s not often that resonance or LFO depth are found as modulation destinations at this price, but it’s even rarer to have a voltage–controllable delay. Routing the LFO or envelope to the echo time may be just the start of many happy hours of cosmic experimentation. Using an external CV mixer (or cheating with a multi) you can combine both sources and unleash epic bouts of flangey chorus that morph into metallic bathrooms and noisy repeats. For self–triggering drones, patch the LFO into the gate input. And so on.

Finally, the patchbay adds the unexpected bonus of extending the depth of available modulation. For example, by connecting the mod wheel to LFO depth you can achieve a far deeper modulation than is possible from the LFO’s unaided depth control.

Conclusion

The Erebus combines two well–matched partners: a big–sounding analogue monosynth and delay. It isn’t always strictly mono either — the duophonic mode not only differentiates it from comparable rivals but bestows a sense of purpose that cuts through some of the design limitations. The synthesis is never complicated but still contains surprise luxuries such as the twin envelopes and glide controls. Then again, there are omissions that frustrate, not least the lack of auto-glide, which is restrictive for those of us keen to employ the Erebus as a source of monster acid bass.

If you’re shopping based on a tick list then the lack of noise generator, pulse–width modulation or oscillator sync might imply the Erebus is underpowered, but in practice, this rarely feels the case. The MIDI implementation is basic but adequate, the filter is a delight and the LFO blissfully slothful. For a variety of solo and bass duties, the Erebus shines but its real strength could be in psychedelia. A couple of subtly detuned sawtooth waves and a slowly swept resonant filter work wonders every time, especially when bathed in wavering echo. Admittedly, the latter is anything but hi–fi, but it’s an ideal sequence–energiser or source of extreme sound effects.

The Dreadbox Erebus is a solid and appealing synthesizer. Its patchbay talks nicely to Euro gear, MS20 Minis and the rest, ensuring greater versatility than its modest footprint would initially suggest. At the price, it’s a very tempting offering.

Alternatives

There are now numerous compact analogue synthesizers vying for our attention, each with its own sound and feature set. Perhaps the closest alternative is the Vermona Mono Lancet; it, too, is fat and uncomplicated, its own CV access offered via a 25–pin extension port and Euro–dock. Or there’s the Doepfer Dark Energy Mk2, a single-oscillator synth with one envelope and two LFOs, plus patch points and MIDI. Open your wallet a little wider and you enter the realm of the Moog Minitaur, Korg MS20 Mini, and so on.

Published August 2015