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Hypersynth Xenophone

Analogue Synthesizer
Published July 2016
By Paul Nagle

Hypersynth Xenophone

In a world of reissues and recreations, the Hypersynth Xenophone is resolutely doing its own thing.

We’ve been served so many variations on the theme of ‘subtractive analogue’ that it’s tempting to assume there’s nothing left to say. The Xenophone is a monophonic/duophonic synthesizer from mystical Persia and it aims to challenge that assumption — and a few more besides. Armed with discrete circuitry, the Xenophone maintains an analogue signal path right up to its 24-bit effects. It offers full MIDI control of every parameter, plus a smattering of CV too, and is powered by three intriguing DCOs and two slightly unusual sub oscillators. Hypersynth’s tabletop box boasts a sizzling multimode filter, software envelopes and LFOs, plus an arpeggiator that can impersonate a multi-lane step sequencer.

PC users are offered a free editor that runs stand-alone or as a VST, but if you have a Mac, you’ll need to be patient a while yet (Q3 2016 is the rough estimate). Those who prefer the more traditional hands-on control are invited to grapple with hardware and more buttons, encoders and LEDs than many larger synths can boast. Which, as it happens, is exactly our kind of invitation!

Arabian Lights

Nobody could accuse Hypersynth of skimping or failing to fill the panel space. With the exception of MIDI reception status, every conceivable function has an LED. That’s 88 of them — all potentially dazzling! Fortunately, they are of variable intensity and ultimately less troublesome to the eye than the tiny ‘select’ buttons, whose black-on-black colour scheme was completely lost in my gloomy man-cave.

As well as a host of dedicated controls, you’ll find four multi-purpose encoders (E1-E4) positioned beneath the 2x20 blue OLED display. The encoders are utilised by the active envelope or by other functions for which no dedicated encoder or switch exists. Personally, I found the sharing of envelope controls far from ideal, probably due to my habit of toggling between filter and amp envelopes repeatedly. If you, too, are in danger of wearing out your button finger, I recommend studying the downloadable manual and the alternate way of getting around — the menu system. Fellow envelope fetishists will appreciate one shortcut in particular: the Xenophone remembers the last envelope edited. Therefore, at any time you can switch from tweaking another area and return to it with a single button press.

Surely the most puzzling aspect of the interface relates to the way the E1-E4 encoders are employed. The general rule is actually quite simple: if a dedicated encoder or button exists, you must use it. Adapting to this is seemed unnatural at first though. For example, supposing you adjust the filter cutoff frequency, the action will update the display to show the four values relevant to the filter section — ie. envelope depth, cutoff, resonance and keytracking. However, of the four soft encoders, only E4 responds to your touch — because only keytracking has no panel control. Once you get over this, you very quickly learn the position of every dedicated control.

The encoders are high-resolution, multi-turn types, but those of the review model were solid black rather than the cool, grey-ringed examples on Hypersynth’s web site. The filter is of 12-bit resolution (using NRPNs) and divided into a whopping 4096 steps rather than the 128 available to a regular 7-bit CC. Little stepping is evident — other than from the bi-polar filter envelope depth encoder. If you switch on the transmission of MIDI CCs & NRPNs, you can capture complete performances into your DAW or hardware sequencer.

If you like a bit of wood with your analogue, the Xenophone can be supported by two types of wooden end-cheeks. It’s up to you whether to order the stylish angled versions (that lift the synth from the desktop) or opt for the standard flat look. On the rear of the synth are the balanced stereo outputs, audio input and headphone jack, plus a single stereo jack catering (in a way) for CV/Gate In/Out. A main volume knob is tucked away back there too, joined by the USB port and MIDI In and Out sockets. Predictably, the power supply is external but I was relieved to learn the temperamental version supplied for review has now been superseded.

Hyper Active

Armed with seven memory banks, the Xenophone can hold a total of 896 sounds! Unsurprisingly, most of the banks are initially empty, but a tour through the populated quarters reveals a synth with biting, floor-wobbling oscillators, clear highs and a squelchy, mud-through-your-toes kind of filter. With intelligent use made of the sequencer, analogue distortion and other effects, the Xenophone has a surprisingly ‘produced’ sound out of the box. The experience left me eager to plough ahead and make noises of my own.

Starting with the two main DCOs, they’re a sophisticated pair offering familiar and unfamiliar analogue waveforms over a massive 10-octave range. Unusually, each offers phase-locking and full control of starting phase — desirable attributes when designing precision bass lines requiring consistent energy. Several waveforms consist of combinations (eg. sawtooth and square); these are blended by a waveshaper circuit, resulting in extended tonality if compared to a simple mixer. Both the blend amount and the pulse width of the square wave component can be freely modulated.

Already this throws up fresh tonal avenues to explore but for weirder paths still, I recommend the catchily-named Xor1-2. Only found in DCO1, this consists of the ring-modulated output of square waves plucked from both main DCOs. It’s dirty, limited and reminiscent of the Korg MS20’s ring mod, but it’s a fine example of squeezing extra juice from regular analogue waveforms.

DCO1 and 2 are boosted by sub oscillators that continue the theme of innovation. As expected, they deliver square waves at one or two octaves below the main but in addition, they indulge in a spot of ring modulation. Each involves the primary oscillator and a sub two or four octaves down but, fortunately, you needn’t know what’s involved to appreciate the hard-edged and buzzy waveforms. While not instantly life-changing, I found them valuable additions as I got to grips with the intricacies of Xenophone programming.

There’s a third oscillator (of lesser stature) too. DCO3 produces either a basic square wave or noise. Although simple, it offers a full 10 octaves of shift — and noise connoisseurs will enjoy the white, pink and roaring red output before flipping over the crunchy, pitch-trackable ‘C=64’ noise. (It’s inspired by the SID chip from the Commodore 64.)

The Xenophone’s back panel features a USB port, MIDI I/O and quarter-inch sockets for CV/Gate I/O, audio in, audio out and headphones. The main volume control is also found here.The Xenophone’s back panel features a USB port, MIDI I/O and quarter-inch sockets for CV/Gate I/O, audio in, audio out and headphones. The main volume control is also found here.

Navigating to the Voice menu, you’ll see an option rare in DCO synths: FM. The implementation is slightly restricted in that you can only modulate DCO1 with a triangle wave extracted from DCO2. The manual advises that for ‘best results’ DCO1 should be a square wave, and it’s right because the results are strangely subdued with other waves. In its favour, high levels of FM will trash DCO1’s sub oscillator in freaky and unexpected ways.

The Voice menu holds more goodies: Detune and Analog Drift. The former skews the pitch of the two main oscillators in opposite directions leaving the third unshifted. Drift nudges all oscillators away from the strict tuning imposed by the Xenophone’s microprocessor. At their most thoroughly nudged, they become very un-DCO-like indeed. Portamento is available in fixed mode or is scaled according to the distance between played notes. The Xenophone is therefore equally applicable to prog-rock wankery or slidey 303 bass lines.

Last but not least, DCO1 can be hard-synchronised to DCO2. Sync is a source of spiky new tonalities but, in keeping with the Xenophone’s unusual nature, the slaved oscillator all but disappears when the two oscillators are the same pitch. Interestingly, the sync operation works very smoothly on a DCO slave, but produces audible steps on the sub-oscillator component.

The oscillators aren’t the full extent of the available audio palette; joining them in the mixer is another ring modulator (a regular one that isn’t fixated on square waves) and an external feedback loop. If you insert a lead into the audio input — eg. to process another synth or drum machine — the feedback loop is interrupted. Otherwise, feedback level becomes a significant contributor to the Xenophone’s audio shaping and is closely related to the current filter mode.

With so many possible sources, the mixer is easily overdriven even before you boost the feedback or resonance. I was seriously impressed by the scope for howling, saturated tones by the simple act of varying the input levels.

The Filter

After breezing through the demo patches, I was already seriously intrigued by the multimode filter. Hypersynth’s acidic design is notable for maintaining its power even when you wind up the resonance. It includes the familiar low-pass, high-pass, band-pass and notch modes, and there are three slopes available (12, 18 and 24 dB) to the low-pass and high-pass. While all were brimming with analogue vitality, I found the band-pass mode the least appealing, but even that was saved by ramping up the feedback and resonance, exposing its harder edge. The notch filter is a fine example of the breed and with high resonance and a touch of feedback it rips like a B-movie masked maniac.

Rounding off the available modes are a couple of low-pass filters placed before a 6dB high-pass — they cut through like a rusty scalpel. At high resonance, most filter modes are capable of self-oscillation, but in these serial modes, the resulting waveforms are a triangle and clipped triangle wave respectively, rather than a regular sine.

Now seemed the opportune moment to prod the filter FM button, enabling DCO1 as a modulation source. The button removes the oscillator from the audio path but its presence is still keenly felt, especially on a self-oscillating filter. My afternoon faded into evening in a blaze of FM-based percussion, with killer results obtained from even basic connections such as velocity controlling pitch or the modulation envelope driving feedback.

In less than half a day, I created almost 50 patches of the aggressive, slicing, tearing persuasion and felt I was homing in on the Xenophone’s sweet spot. For me it excels at dark, acidic bass, screaming solos and every strain of wonky, glitchy cross mod and ring mod. It’s also very capable of generating classic mellow, brassy leads if you’re that way inclined. Incidentally, here’s a tip I really took to heart after overwriting several patches by accident. The default ‘save location’ is the last one specified. However, if you turn the E1 encoder prior to saving, the destination becomes the current source instead.

Pushing The Envelope

Ordinarily, you might take modulation for granted. With a trio of envelopes and LFOs, plus a modulation matrix to hook everything together, you might feel there’s nothing to discover, but that would be to miss a treat. Several, actually.

The DAHDSR envelopes deserve attention, and not just because of those extra hold stages. Other options are but a menu page away, and they’re options rarely seen and even more rarely appreciated. For a start there are four styles to choose from, essentially choices of envelope shape. These are: linear, exponential and a pair of ‘RC’ shapes. The last two are aimed at replicating the distinctive curve of capacitor charge and discharge found in vintage synths — great stuff!

Better still, you can independently select the way each envelope is triggered. The options are to reset the envelope level on every key-press or to maintain the level only when you play legato, but it’s the final two modes that hit pay dirt. In either of these ‘analogue’ modes, the envelope acts like a classic single or multi-triggering synth. The crucial difference between this and other behaviours is that the envelope level is not constantly reset to zero. Not only is this essential to the enjoyment of long attack and release values, it neatly avoids the clicks that invariably accompany the ‘zero-ing’ type of envelope. (Owners of Korg’s Minilogue will know what I’m talking about.)

The Xenophone’s front panel measures 328 x 167 mm.The Xenophone’s front panel measures 328 x 167 mm.

With envelope times ranging between 1ms and almost 30s and built-in velocity control for the amp envelope, there’s much to applaud, but there’s more. Each envelope can be restarted by LFO2 (with the weird condition of sample & hold being selected) or by MIDI CC64. Of more practical value, the envelopes’ attack and decay stages are loopable, and with such fast envelopes, a looping envelope becomes another audio-level modulation source. Finally, if you take release to its maximum, the envelope enters a special hold mode. This is ideal for processing external signals by the filters and effects as it bypasses the requirement to keep hitting a key.

More Modulation

With three LFOs to play with, it’s no great hardship that LFO 1 and 2 share controls and targets, but some other limitations are less palatable. For example, only LFO1 and LFO3 have built-in (although menu-bound) depth controls. Encoders and buttons are allocated to speed, waveform and target selection, but if you want any modulation it involves entering a menu.

All the usual waveforms are offered and each LFO can run freely, sync to the current tempo or be restarted by playing a note. Their range is from stopped to just below 100Hz. In order to make use of LFO2 or the third envelope, you’ll need one of the eight precious modulation slots. A slot consists of a single connection between any of the 40 sources and an impressive number of targets. In practice, it doesn’t take long to use them all up — the LEDs are a helpful reminder of which are taken.

Amongst the potential sources are several useful combinations, such as LFOs that are multiplied by the value of the mod wheel, by each other or by the mod envelope. For further versatility, modulation targets include the envelope stages, the depths of the first four matrix slots and even some effect parameters.

The modulation matrix is also where you go to assign incoming or outgoing CV. Examples of this are to direct one of the Xenophone’s internal modulation sources to another synth, or to draw modulation in from an external source. Although it is possible to use the Xenophone as a MIDI to CV interface (I successfully drove my faithful Roland SH101 from it), you can’t play it — in tune anyway — from an external CV/Gate synth or sequencer. I’m informed this is due to a limitation of the DCO design.

Arpeggiator/Sequencer

The arpeggiator has no immediately obvious panel control to switch it on or off. Instead you press the relevant Select button until you reach the menu page with ‘Span’ on it. Span’s options are: Off, Up, Down, Up/Down, Step and Ordered, and when you pick anything but ‘Off’, the arpeggiator kicks into life. There’s no ‘random’ direction but when you pick ‘Step’, the arpeggiator becomes a step sequencer, it patterns up to 16 steps.

When in sequencer mode, the pattern plays as soon as you play a note or, providing Latch isn’t enabled, you can stop, preview and pause using the mini transport keys. Each sequence step contains a note and velocity — or simply a rest — plus two ‘auxiliary’ values. The auxiliaries are unassigned at first but, since all four rows are available sources in the modulation matrix, they are powerful tools for introducing movement and modulation. To exploit this idea further, the sequencer can be flipped to ‘Step LFO’ mode, in which pitch and velocity control is disabled, leaving all four rows for any purpose you like. I said those eight matrix entries were quickly used up!

Hold can be added to any step, and slew introduced to smooth the otherwise abrupt transitions from step to step. Sequences can be transposed by keyboard input and notes entered from a keyboard too, unless you prefer step-by-step entry from a menu.

Effects

Not many analogue monophonic synths have built-in effects and typically, when they do, it’s a basic delay of some kind. Hypersynth’s effects consist of analogue distortion plus a 24-bit digital reverb and delay. There’s no balance of distortion to signal, just an on/off button, so it’s a challenge to introduce subtly. Distortion has a crude transistor feel and goes from ‘light’ to ‘massive’ in a mere four button presses, each adding volume, body and a progressively harder-edged distortion.

The effects include five reverbs (room, hall, cathedral, gated and plate), plus two delays and a combined delay and reverb. Some algorithms are more tweakable than others but who’d deny the sheer usefulness of built-in effects, especially for live performance? The reverbs are particularly good, especially the vast and magnificent cathedral. The parameters (pre-delay, time and damping) are assigned arbitrary values in the range 0-200 but they aren’t hard to master. With a maximum time of 1 second and a pleasant ping-pong mode, the delays are somehow less impressive but still handy, especially in tempo-synced mode.

Duophony

A software update arrived as I was almost wrapping up. It contained several important bug fixes (shortening the review somewhat) and a sweetener in the form of a new duophonic mode (lengthening it right here). Naturally this has a twist; when ‘Duo’ is enabled, ordinary monophonic playing acts on DCO1 alone, but when you play a second note this brings in DCO2 and 3 together. The approach feels more natural than duophonic implementations in which all oscillators play until you hit that second note, when they are divided. However, perhaps the most important characteristic of the implementation is the drafting in of two separate amp envelopes and VCAs to shape the voices before they hit the filter. Each is individually velocity responsive. This presents the possibility to play and hold a note that will decay naturally while playing a solo over the top. Of course, you’re still limited to a single filter, but as each oscillator may have different waveforms and be modulated separately, drone and solo combinations work better than on many duophonic synths.

Conclusion

Digging into the Xenophone’s Greek roots, they translate to either ‘different’ or ‘foreign’ plus ‘voice’ or ‘sound’. By my reckoning this nails it. The Xenophone is indeed different enough to offset potential analogue fatigue. It’s a refreshing break from Moog-like traditions and thanks to those extra waveform choices, FM of filter and oscillator and the chewy multi-mode filter, it deserves to win many friends. Although DCO synths are sometimes viewed as less ‘alive’ than VCOs, that opinion seems increasingly stale in the light of synths like this which can deliver fat, trans-Atlantic basses and swooshy leads galore, optionally bathed in lush reverb and sequenced if necessary.

I’m sorry I couldn’t try the XEditor plug-in but, despite its menus, the Xenophone is accessible enough anyway. However, it is not a budget synth nor is it necessarily the easiest to warm to. As my personal preference tends to be knobs over encoders, I admit my first days were marked with frustration over aspects of the encoder behaviour. Fortunately, this feeling soon passed, but Hypersynth say they are considering opening up all the soft encoders in a future update. And speaking of updates, duophony was a late surprise, but a very welcome one! If you like a little spice and mystery with your analogue, the Xenophone could prove irresistibly moreish.

Alternatives

The less expensive but more menu-bound Waldorf Pulse 2 springs to mind as competition. Despite its minimal interface, the Pulse 2’s triple DCO design, paraphony and extensive modulation matrix offer considerable flexibility, but it lacks the effects, step sequencer and sweet filter modes of the Xenophone. Other contenders include the Studio Electronics Boomstar range: they’re based on the oscillators and filters of classic synths of old but are comparably priced and can be driven by CV/Gate. The Boomstar’s direct, knobby interface is in stark contrast to the encoders, MIDI control and patch memories of the Xenophone.

Editor

Xenophone's XEditor.Xenophone's XEditor.

PC users are offered XEditor, a free stand-alone editor and VST plug-in to reveal every corner of this Aladdin’s cave. I’d love to offer my thoughts on it but unfortunately there’s no Mac version currently available. The Xenophone is not a class-compliant device either, so you’ll need to digest the instructions on the Hypersynth web site before using the USB MIDI connectivity and performing firmware updates. Fortunately, although the latter process is more complex than usual, it’s well-documented.

MIDI

Every aspect of the Xenophone may be harnessed by MIDI. This includes the four sequencer rows, effect parameters and even the modulation matrix entries. Some of the MIDI implementation is a little quirky, eg. CC10 (which you’d expect to control pan) is assigned to DCO1’s phase but CC8 (balance) is employed to move the output — effects and all — around the stereo spectrum.

Published July 2016

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