ASM Hydrasynth Explorer & Deluxe

ASM expand their popular Hydrasynth range with two new options.

Three years is not a long time. Yet, in that short period, Ashun Sound Machines (ASM) have managed to sneak one of their excellent Hydrasynths into half of the studios I know. The Hydrasynth is an 8‑voice digital synth often categorised as a wavetable synth, although it isn’t really. In his May 2020 review, Paul Nagle praised it for its unique approach to digital synthesis, solid build, and inclusion of polyphonic aftertouch. I am fairly sure Paul still has one in his studio.

The Hydrasynth appears to have sold well for ASM. Well enough, it seems, to expand the range. The new Explorer and Deluxe versions join the original Keyboard and Desktop models to make a total of four Hydrasynths from which to choose.

The Explorer is the baby of the bunch — the most cost‑effective way to jump on the Hydrasynth train. Its compact design, mini‑keys and reduced number of controls make it the perfect choice for anyone constrained by budget or space. The Deluxe, on the other hand, is the Rolls Royce of the group, with a six‑octave semi‑weighted keyboard and dual synth engines, giving you two Hydrasynths in one high‑end package.

ASM Hydrasynth Explorer

Let’s Rehydrate

We won’t go into the fine detail of our original Hydrasynth review, but a recap is undoubtedly helpful. All Hydrasynth models share the same powerful synthesis engine. Everything revolves around three oscillators capable of wave‑scanning, FM and virtual‑analogue synthesis. There’s 8‑voice polyphony in all models except the new Deluxe, which gives you 16.

The Hydrasynths are often referred to as wavetable synthesizers, although this isn’t strictly accurate. Wave‑scanning allows you to choose up to eight static digital waveforms and morph between them. The sonic result is similar to wavetables, even though you can’t save or import your own.

Two of the three oscillators can be further manipulated by an independent pair of ‘mutant’ modules. Each module can choose one of eight processors, including FM, phase‑shifting, unison, sync, pulse‑width modulation, and other harmonic treatments. Ring modulation and noise can also be added before the mixed signal passes to the dual filters.

There is a healthy number of digital filter types. There are various flavours of low‑, band‑, and high‑pass filters, and even a vowel filter. They sound excellent, whether routed in series or parallel. Filters can be overdriven for analogue‑style saturation too. One aspect of digital synths I appreciate over their analogue counterparts is a stereo signal path, which is present here. Any audio signal can be panned before it reaches the filters, and that stereo information will be maintained for the rest of the signal path.

Many modulation sources are available to add movement to your sound, including five LFOs, five envelopes, and the usual MIDI suspects. All of which are handled by a generous 32‑slot modulation matrix.

Hydrasynths offer four effects slots, which can all be active at once. There are two multi‑effects slots with flanger, chorus, phaser, rotary, lo‑fi, tremolo, EQ, compression and distortion, plus dedicated reverb and delay slots. I’m not usually a fan of onboard effects on synthesizers, but here they sound impressive and are flexible enough to feel like part of the synthesis rather than a cheap add‑on.

ASM round off the synthesis options with a moderately powerful arpeggiator. The usual modes and options are present, as well as some more unusual options like chord mode, phrase mode (64 to choose from), cycle length, octave ordering modes, and ratchets with probability. I’m not usually a fan of arpeggiators, either. However, ASM have provided enough bells and whistles to easily avoid the cliché patterns we’ve heard a thousand times before.

For those who like to embrace the chaos, there’s a rather clever randomiser too. You can randomise a whole patch or decide which modules to include or exclude and by what percentage.

Workflow

The workflow is consistent throughout the line‑up. A group of buttons for each synthesis section is laid out to represent the signal flow. Press a button, for example OSC1 or LFO, then edit specific parameters on the larger of the two screens. The Deluxe, Keyboard and Desktop versions can all display and edit up to eight parameters at once without having to tab to additional screens. The Explorer shows just four parameters per screen, potentially doubling the number of button presses needed to access all the parameters.

The shortcut buttons are also used to assign modulation. You can hold down the shortcut button for, say, LFO, then press the OSC1 button. This creates a modulation slot with source and destination pre‑assigned. All that’s left to do is pick the parameter from OSC1 that you wish to modulate, and set a depth. It’s a great system and one that works equally well on all the Hydrasynth models.

The Explorer offers five banks of 128 presets, all of which are filled, so if you want to program your own presets, you’ll have to save over some factory content. You could also use the ASM Hydrasynth Manager software to backup sounds on your Mac or PC. It’s not a full editor, but that’s ok because editing on the synths themselves is a pleasure. The Deluxe comes with the same five banks of Single presets, plus three extra banks which are pleasingly empty, and five banks of Multi presets, two of which are filled with factory presets.

Explorer Specifics

The Explorer is aimed at budget‑ or space‑conscious customers, with a three‑octave mini‑keybed. Impressively, these mini‑keys are still able to deliver polyphonic aftertouch, although it is not as controllable as the response offered by the Keyboard and Deluxe keybeds. It weighs 3.5kg, roughly the same as the Desktop model, although it is slightly bigger.

As you might expect, the Explorer has fewer controls, but the knobs are still panel‑mounted and feel robust. The Master Control section knobs no longer have the LED skirts found on the bigger models, which is a shame, but understandable.

The hard plastic buttons of the other Hydrasynths have been replaced with soft rubberised alternatives. I presume this is a cost‑saving measure, but they honestly don’t feel like a downgrade. If you want portability, the Explorer is the only model that can be battery‑powered with eight AAs.

Instead of pitch and modulation wheels, the Explorer offers touch‑strips, which are OK but less precise. I’m not a huge fan, but they’ll do. It does not have the ribbon controller from the Keyboard and Deluxe, or the CV inputs, which double as audio inputs. Finally, if you need a MIDI thru port or an expression pedal input, you won’t find them here either.

One aspect of the Explorer design which struck me as odd is that the screens are not aligned. ‘So what?’ you might think. On the other models, the screens are horizontally aligned, making them feel connected. It probably wouldn’t bother you if you bought an Explorer without trying another model, but it seems like an elegant design choice that has been compromised in the smaller form factor.

Despite the reduced number of controls, programming doesn’t feel crippled, as is often the case on budget models of larger synthesizers. ASM have kept what’s important. As a result, the Explorer still feels like a proper synth.

ASM have made no sacrifices to the core sound engine on any version of Hydrasynth. The new Explorer contains all the same sounds as the Keyboard and Desktop models. And the Deluxe simply gives you more of everything.

Deluxe Specifics

As its name suggests, the Deluxe lives at the other end of the spectrum. Its six‑octave full‑sized keyboard, dual synthesis engines, all‑metal construction and steel grey side‑cheeks add a premium feel. It’s hefty, too, weighing in at 13.3kg. The front‑panel layout is mostly the same as the Keyboard and Desktop models, with a couple of extra controls for selecting layers and additional space to the right that comfortably accommodates a small synth, drum machine, effect box or laptop. It even comes with a neat ‘shelf extender’ to attach to the back if you need more space.

The biggest draw will be the dual synthesis engine. The Deluxe is two Hydrasynths in one, with the ability layer or split (with optional crossfades). If you prefer, you can engage Single mode, which gives all 16 voices to a single layer. Bi‑timbral operation is also available if you want to sequence two completely different sounds via separate MIDI channels. And there are two stereo outputs so that you can process both layers externally — thumbs up.

Operationally, this twin personality couldn’t be more straightforward. The extra controls just above the wheels allow you to select a layer to edit (or both, if required). The Balance knob controls the volume between the two. A new preset type, the Multi, allows you to save a pair of presets and their layering information.

Besides this, the Deluxe is what we already know from the Keyboard version. I was glad to see that the headphone outputs have been moved to the front of the Deluxe. On all other models, they are found on the rear.

A minor addition to the Deluxe and Explorer models is support for note‑off velocity. Limitations in the original Keyboard design meant this was impossible, although it could be assigned in the modulation matrix and triggered from an external keyboard. The Deluxe and Explorer keybeds can now support this natively. Perhaps unsurprisingly, I found it much more reliable on the more expensive Deluxe keybed.

The Deluxe is beautifully built, and its ability to layer two Hydrasynth engines turns it into a sound design powerhouse. Of course, not everyone will have room for such a large synthesizer. Perhaps ASM might introduce a ‘Deluxe Desktop’ in the future, with the benefits of a dual engine in a smaller package.

Conclusions

The Hydrasynth is a popular synthesizer for a good reason. It combines elements of wavetable, FM and subtractive synthesis without being any of those things. It sticks to pure synthesis, resisting the urge to add anything that might dilute the purity of that ethos. There are nice touches and thoughtful design decisions wherever you look.

Soundwise, the Hydrasynth sounds highly electronic. Maybe that’s a dumb thing to say, but it’s worth pointing out. There are no pianos (well, perhaps the occasional electric piano emulation), no acoustic strings, no brass samples, no guitars. It’s a synthesist’s wet dream. If your idea of fun is cross‑modulating two sine waves, applying hard sync, morphing each wave into a multitude of other shapes, ring modulating, and then putting it all through a series of excellent effects, well, this is the synth for you.

ASM have made no sacrifices to the core sound engine on any version of Hydrasynth. The new Explorer contains all the same sounds as the Keyboard and Desktop models. And the Deluxe simply gives you more of everything.

I was impressed with both synths for different reasons. The Explorer offers fantastic value without feeling like a toy. And the Deluxe lives up to its name — the experience is luxurious.

The decision of which Hydrasynth to buy likely comes down to which form factor makes sense to you, perhaps with a dash of bank balance thrown in. Do you need a keyboard? If so, should they be full‑sized keys? Do you want a ribbon controller? Are audio inputs necessary? Do you need keyboard splits? Or perhaps bragging rights at having double the polyphony your friend has are top of your list. Answer these questions, and you’ll likely find there’s a Hydrasynth that’s right for you.