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Dave Smith Instruments Mopho

Analogue Synthesizer
Published August 2009
By Gordon Reid

The latest synth from Dave Smith owes more than a little to its illustrious ancestor, the Sequential Circuits Pro One, but costs only £299$399.

Dave Smith Instruments Mopho

Last year I reviewed the DSI Prophet 08. To my pleasure, I was able to give it an almost unreserved 'thumbs‑up', so I have to admit that I am a little surprised at how few I see on stage and in the studios I visit. But if the Prophet 08 — which in many ways replaces vintage polysynths such as the Prophet 5, 10, 600 and T8 — has not been as widely adopted as I had envisaged, maybe it would have been different if DSI had manufactured a low‑cost successor to the Pro One.

Unsurprisingly, I haven't been the only one thinking along these lines, because here it is. But it's not the keyboard‑based monosynth you might have expected, it's a small yellow box that looks more like an effects unit than an instrument. It's the DSI MOnoPHOnic synthesizer, or Mopho for short.

First Impressions

The SoundEditor software shows you all of the synth's voicing parameters on a single screen and provides a far easier way to program the Mopho.The SoundEditor software shows you all of the synth's voicing parameters on a single screen and provides a far easier way to program the Mopho.

Physically, there's not a lot to the Mopho. Looking as if someone has hewn it from a section of a Waldorf Q control panel, it offers just 10 rotary encoders (including four assignable performance knobs), two potentiometers (input gain and output volume), six buttons and a 2x16‑character screen. Round the back there are quarter‑inch sockets for the audio input (which also generates a gate signal and acts as an envelope follower), audio out (left & right) and headphones, MIDI In and Out DIN sockets (the latter of which can double as a Thru) and a socket for a 13V DC adaptor. For an instrument of this size and price, the use of a wall‑wart is acceptable, but there's no on/off switch, so the only ways to switch the Mopho off are at the mains socket or by pulling out the power connector, both of which generate a thunk. I appreciate that the build cost was kept to a minimum, but this is one area in which I think that DSI have gone a bit too far.

Some people have already described the Mopho as one voice of a Prophet 08 and to a large extent that's correct. Its dual oscillators are DCOs, its low‑pass filter is on the same chip manufactured for the 08, and the four LFOs and three contour generators are calculated digitally and then converted to control voltages. Indeed, the similarities between the Prophet 08 and the Mopho are so great that you can use the control surface of an 08 as a programmer for its little brother. But there are differences between the two. Most obviously, the Mopho adds a useful square wave sub‑oscillator to each oscillator, a handful more modulation sources and destinations, and it has an external audio input, the lack of which was one of the few deficiencies of the 08. On the other hand, the Mopho omits a few of the 08's refinements such as user‑selectable velocity‑ and pressure‑response curves. Nevertheless, if you approach the Mopho as a monophonic 08, just as the Pro One was regarded as the monophonic Prophet 5, you'll not go far wrong. Indeed, open up a Mopho, and written on the motherboard is says 'Pro One II'. You can't have stronger confirmation than that!

Making Sounds

The SoundEditor's view of the Mopho's four‑line, 16‑step sequencer.The SoundEditor's view of the Mopho's four‑line, 16‑step sequencer.

With this in mind, I placed the Mopho and a controller keyboard next to my Pro One and started the review by comparing their sawtooth, triangle waves and pulse waves (the last at various widths) all with the filters wide open. Although there were differences, these were too small to care about. Of course the Mopho has those sub‑oscillators and the Pro One can generate multiple waveforms simultaneously but, fundamentally, the two instruments can sound very similar.

Although the OnChip filter in the Mopho is a descendent of the CEM3320 chip used in the Pro One, the sonic differences between the two synths are a bit more noticeable here, especially when you ask the filters to jump through some of their more esoteric hoops. But when I patched some filter‑dominated lead and bass patches on the Pro One I found that I could emulate all of them closely on the Mopho.

Nonetheless, the Mopho can enter timbral territory forever denied to the Pro One because its filter has two modes: the traditional 24dB/octave mode and a less aggressive 12dB/octave mode. With no resonance applied, the differences between these are not as great as you might expect. But when you apply resonance, their true characters are revealed. The 24dB/octave mode will whistle, whine and shriek with the best of them, happily self‑oscillating at higher resonance values. The 12dB/octave mode refuses to be so vulgar, and delivers a refined timbre that I like a lot.

Although the principles of filtering and warping external audio signals using a synthesizer are well understood, the Mopho has a rather neat trick up its hybrid sleeve. When no jack plug is inserted into its Audio In socket, its left output is internally routed to the input, creating a feedback loop that's controlled by the Input Gain knob and the Ext In Vol parameter in the oscillator section. At one extreme, this can subtly enhance your sounds. At the other, it leads to sonic mayhem. This gives the Mopho a very significant edge over many other synthesizers, and I think you're really going to like it.

Program Genetics lets you 'breed' new sounds from two different ones. Disturbing terminology aside, it's a useful way to get unexpected results.Program Genetics lets you 'breed' new sounds from two different ones. Disturbing terminology aside, it's a useful way to get unexpected results.Once the Mopho and the Pro One have begun to diverge, there's no stopping them. Whereas the Pro One had four keying modes and a pair of ADSR contour generators, the Mopho has six keying modes and three DADSR generators; one for the VCA, one for the filter, and one that you can assign to any of the Mopho's 46 modulation destinations. All three contours are velocity‑sensitive by default (the Pro One was not) and their times, levels and amounts can themselves be the destinations for the Mopho's 22 modulation sources. Oh yes... and Envelope 3 also has a repeat mode, so you can use this as a cyclic modulator.

Mind you, you're not short of dedicated LFOs on the Mopho. The Pro One had just one that could be directed to five destinations, but this also had to double as the clock for the on‑board arpeggiator and sequencer. The Mopho steps way beyond this, with four LFOs that range from around two cycles per minute to audio frequencies. They offer MIDI sync with a wide range of options, and each can be directed to the full list of modulation destinations. You can even assign an LFO to multiple destinations simultaneously using the eight‑slot modulation matrix, which allows you to direct any of the modulation sources to any of the destinations, each with individually defined amounts. In addition, a second matrix directs the five most important performance parameters — mod wheel, velocity, aftertouch, breath controller and foot‑pedal controller — to the 46 destinations.

In sharp contrast to the Mopho's massive synthesis power, its arpeggiator is extremely basic. Although it can be clocked by MIDI, it's gated (which means that it only plays when a key is depressed or a MIDI Note On is received), it has no random mode, and you cannot extend it over multiple octaves. This is very odd when you consider the flexibility of the rest of the control software. Much better is the very useable four‑line, 16‑step sequencer, which in many ways imitates classic analogue devices such as the ARP 1601 and Analogue Systems TH48.

The Editor

The Mopho's rear panel features (from left to right) headphone out, left and right audio outputs, audio input, MIDI In and Out/Thru and a socket for the 13V external power supply.The Mopho's rear panel features (from left to right) headphone out, left and right audio outputs, audio input, MIDI In and Out/Thru and a socket for the 13V external power supply.

Although any parameter‑access programming system is a pain in the posterior, it's a necessary evil on a unit as small as this, and at least the implementation on the Mopho has no sub‑menus or arcana to annoy you, just a linear menu with 110 parameters within it. To program it from its top panel, you scroll to the desired parameter, press the Assign Parameter button, and then adjust its value.

The Mopho comes alive, however, when you program it using the free Mac and PC editor/librarian software (Mopho SoundEditor LE) that you can download from While this doesn't offer all the features of the full version (for which a software key can be purchased for $40) it allows you to see all of the synth's voicing parameters on a single screen, which is excellent.

I downloaded the LE version and this ran on my MacBook Pro without problems, although I initially found it difficult to get the editor, the Mopho and the controller keyboard to talk to each other simultaneously. The answer was a bit of clever routing in my emergency‑toolbox‑​that‑sorts‑out‑everything, Plogue Bidule. If you don't have this or something equivalent, DSI's technical support people can explain how to use a host DAW or (on a Mac) the IAC drivers to get everything working together.

The primary screen makes programming a doddle, and you can even pick up the handles in the contour graphics and drag them around, which is a far cry from the Mopho's internal programming system! A second screen displays a piano keyboard so that you can audition patches on‑screen, and then there's a window for the global parameters, plus the important Sequencer page. Having all four rows and their destinations visible as you work on them makes all the difference.

Like you, I wondered what $40 would buy me, and DSI kindly upgraded me to the Pro version so that I could investigate its three new menu items, namely: Snap, Morpher and Genetics.

Snapshots are instantaneous 'photos' of the current state of the editor, and you can snap these at any time to create a list of your twiddlings. This is much like the History function in packages such as Photoshop, and very useful it is, too. The Morpher allows you to select two patches and to determine the means — such as the mod wheel or a MIDI CC number — for morphing between them in real‑time. Usefully, you can select whether important parameters such as the oscillators and sequences remain unchanged during the morph. This helps you to create meaningful changes rather than sonic confusion. Finally, there's Genetics, which allows you to select two patches (called Mommy and Daddy) and create 128 'children' based upon these by mixing, morphing, 'mutating', or random generation. I'm not a fan of serendipity but, given that the Mopho may be somebody's first genuine synthesizer, Genetics could be a source of all manner of novel sounds.

In theory, the SoundEditor software allows you to update the Mopho's OS. The test unit was delivered with v1.2 installed, and v1.3 was the current version by the time that I completed this review, so I attempted the upgrade as instructed. Unfortunately, while the Mopho started its loading countdown, it immediately aborted, whether routed directly or via Plogue Bidule. It's unclear whether this was a difficulty with my configuration or a bug in the Mopho/SoundEditor, but I suspect that it was the former.

A Few Small Grumbles

The Mopho is very neat, and will fit into any MIDI setup. Nonetheless, it has some minor niggles, so let's get them out of the way...

I would like to see the arpeggiator revamped so that it has more modes, covers multiple octaves, and isn't gated. Likewise, I think that gating should be an option on the sequencer, not the only mode available. Equally unfortunate was the decision to make the filter cutoff frequency parameter range from 0 to 164, the LFO frequency range from 0 to 166, and various contour and modulator amounts range from 0 to 254. While there were valid reasons for doing so, many MIDI controllers generate numbers only between zero and 127, so this could be a problem. I also find the patch management system a bit frustrating. You can allocate each of the memories to a sonic category, but there are no searching capabilities, so it's fairly pointless.

As far as the editor goes, there's work to be done. I found that its virtual knobs respond rather jerkily on my Mac, and there's no way to type parameter values into fields, nor is there a mechanism to jump to sensible default values. Oh yes, and despite undertakings from Soundtower that a manual would arrive in February 2009, the link on their web site is dead. (I eventually found a copy at

A Few Large Compliments

Despite these niggles, the Mopho scores very highly where it matters most. Like the Pro One before it, it has been built down to a price, but it has not been sonically compromised. Set up a patch, assign your controllers, then get stuck in with a velocity‑ and pressure‑ sensitive keyboard and you're cookin'. It produces superb leads and solid basses, as well as solo strings, brass, and all manner of special effects. It's flexible, too... I was amazed at how easily I could emulate some of my favourite ARP Pro Soloist patches as well as the chunkier Prophet‑ and Moog‑style patches that one would expect to be its forté. Of course, the Mopho will also step way beyond the sounds of the '70s and '80s. There's no end of techno lurking within its sync'able sequencer, arpeggiator and LFOs, and the modulation matrix makes it possible to create many sounds that you might not have expected.

It's just a little pressed-steel box with a sticker for a control panel, but the Mopho will make your windows rattle if you ask it to. So, does it recreate the vintage monosynth experience? No, of course not; with a parameter‑access programming system and no keyboard, it can't. But, as was pointed out to me during the course of the review, the nine panel controls (four of which are assignable) permit a great deal of quick and easy real‑time tweaking that will be useful for novices and more experienced players alike. If the Mopho is your first analogue synth, this immediacy‑without‑complexity could be very important.

In conclusion, the Mopho can be warm, deep, harsh, silky, clean, simple, grungy, complex, gentle or aggressive, as you choose, and I can't immediately think of a cheaper or more convenient way to buy a genuine analogue signal path of this quality and flexibility. If you can live with its on‑board programming system interface or you're happy to use it with the editor, you'll find that it's a fine instrument that pleases on many levels. Given the cost of obtaining these sounds from a range of vintage monosynths, you have to take it seriously.  


There have been many MIDI‑controlled analogue rackmount monosynths released since the format became popular in the late 1980s. Of these, perhaps the most notable have been the Studio Electronics SE1, the Waldorf Pulse and, most recently, the Moog Voyager Rackmount. But analogue monosynths in a desktop format have been much rarer. Currently, there are perhaps just two leading competitors for the Mopho.

The first is the MFB‑SYNTH II from Berlin. This is a slightly more expensive desktop module with an analogue signal path that includes three oscillators and a 24dB/octave filter. With the look and feel of a vintage synth, this is more tactile than the Mopho and will appeal to players who prefer to program sounds on the control panel, just as on a vintage synth.

The second comes from the same stable as the Mopho itself; it's the DSI Evolver. This offers four oscillators (of which two are digital and based upon the Prophet VS), but thereafter shares a similar architecture to the Mopho, with a CEM‑based filter and analogue VCAs coupled to digitally generated contours, LFOs and other facilities.

Happily, there's good differentiation between these three, so there should be one that's suitable for almost everybody.

A Revered Ancestor

The Pro One was released in 1981. Although it lacked some of the features offered by its competition, it sounded great and, at under £500, it was cheaper than many other monosynths of the era, so it appealed to wealthy professionals and cash‑strapped musicians alike. Apocrypha suggests that about 10,000 units were built during its four‑year production run, but its user‑list is a Who's Who of the era: Vince Clarke, Bronski Beat, 808 State, Howard Jones, Marillion, and many, many more.

There were a number of changes made to the Pro One during its lifetime. The one used for the comparisons in this review is serial number 6742, which has the better (earlier) keyboard mechanism, and the better (later) motherboard and power supply.

Vital Statistics

  • Oscillators: Two, with sub‑oscillators.
  • Filter: 12dB/octave, 24dB/octave switchable LPF.
  • Contour generators: Three DADSR envelopes.
  • LFOs: Four, with MIDI sync.
  • Internal modulation sources: 22.
  • Internal modulation destinations 46.
  • Arpeggiator: Up, Down, Up/Down, unlatched.
  • Sequencer: Four rows, 16 steps, MIDI sync'ed.
  • Memories: Three banks of 128 patches.
  • MIDI: In, Out/Thru.
  • Audio: Out L & R, In, stereo headphones out.
  • Size: 19 x 13 x 4cm.
  • Weight: 0.7kg.
Published August 2009

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