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Dave Smith Instruments Mopho x4

Review by: Jason D. Buchwald
  Features  Usability  Documentation & Product Support  Price  Other Comments
Contact Info  Overall Rating—Product Summary



Back in 2010, we reviewed the original Mopho keyboard. Offering one voice of DSI’s sonic greatness, we thought it was a great little synth. We did lament, however, that we wished it offered more polyphony because we liked it so much!

Good news, Mopho fans. That day has arrived! The Mopho x4 is a forty-four key, four-voice analog synth. Utilizing the same Curtis chips of so many great analog synth legends, the Mopho brings vintage specs up to the modern day with MIDI and USB connectivity, the ability to “poly-chain” (basically connect to other DSI devices to increase polyphony), an arpeggiator, and of course, great sound, makes this yet another winner for Dave Smith. There’s even a patch editor by SoundTower that comes in free and expanded purchasable versions.

The Mopho x4 offers a great way to get into DSI poly synths without breaking the bank (relative to a Prophet 12, which costs more than twice as much), all while retaining the legendary sound quality these synths are known for.


3.5 Stars

It’s not yellow! The original single-voice Mopho keyboard was neon yellow, but the x4, thankfully, is not [Editor’s Note: I loved the yellow]. It looks quite sharp actually, and feels sturdily made. The solid wood end caps are a nice touch, as is the charcoal gray case with white lettering. The LCD display is yellow, though, so if you love yellow, there you go.

DSI has done a nice job of squeezing a lot of controls into a small space without making things ridiculously tedious. There are eight banks of 128 programs: four banks of factory programs (F1-F4), and four banks of user programs (U1-U4). While all sounds may be edited, changes can only be saved to the User banks (factory banks are read only). The layout is as follows:

To the upper left, off center, is the two-line LED character display. This provides names of patches, banks, parameter info, etc. Whenever any knob is turned, the screen automatically displays what parameter you are changing and what the value is, with your changes being shown in real-time. Below this is the Envelope section. There are three, five-stage (Delay and ADSR) envelope generators per voice. Two are dedicated (one to the filter, the other to the amplifier), and the third is assignable to a modultation parameter of your choice. These three envelopes are toggled between by using a button next to the LED lights that signify which envelope you are editing.

Below this section is the Oscillator panel. The Mopho x4 has two digitally controlled analog oscillators (DCOs) per voice. This gives much greater stability over the analog pathway compared with older analog synths that often used voltage control. Anyone who has ever tried playing an Oberheim OB-8 knows this kind of instability very well! There is a button to select waveform (sawtooth, triangle, saw-tri, square, and off) and there are knobs to control frequency (controls base oscillator over a ten octave range stepping in semitones), fine frequency (for finer tuning up to a quarter tone), pulse width, glide (portamento), sub-octave (which controls the level of a square wave pitched one octave below oscillator 1 or two octaves below oscillator 2). A button toggles between oscillator 1 and 2.

Moving towards the right is the Modulation panel. A button toggles between the LFO, Sequencer, Modulator, and Misc Mod controls. The Mopho x4 has four low frequency modulators (LFOs) per voice. Each LFO can be chosen by a button that toggles between 1-4, and the yellow LED lights up accordingly to the current LFO you are working on. A destination knob lets you choose from a list of possibilities, including LFO frequency, LFO amount, Envelope attack rate, and quite a few others. You may also choose the waveform shape (triangle, reverse sawtooth, sawtooth, square, and sample and hold; sample and hold generates a random value that changes once per cycle). You may also choose frequency, and clock sync.

When the modulator button is toggled, you have four general-purpose modulators to each go to a single destination (again, chosen by the destination knob). If the Misc Mod button is toggled, you are then granted control over dedicated modulators, such as the mod wheel, keyboard aftertouch, and velocity.

Nearby is the Filter panel, which allows you to choose between 2- or 4-pole low pass filters per voice. In 4-pole mode, the low pass filter rolls off frequencies above the cutoff frequency at a slope of 24dB/octave; in 2-pole mode, the slope is 12dB/octave. There are also knobs in this section to control frequency, resonance, Audio Modulation and Key Amount.

Below this is the Mixer panel, and this section balances the levels of the outputs of the Oscillators section and noise generator, and the Audio In/feedback loop before routing the summed signals to the low pass filter. To help understand this, the signal flow is as shown below:


In the mixer section, there are knobs to control the mix of Oscillator 1 and 2 (with a value of 64 being a 50/50 mix), feedback amount, and noise, which controls the amount of the white noise generator.

Toggling the Modulator button to sequence gives you control over the Mopho x4 sequencer. The sequencer is comprised of four, 16-step sequences that play in parallel. Each sequence can be routed to a chosen destination, and each step in a sequence can be set to a different value used to modulate that destination. The four sequences can be different lengths, and you may enter “rests” as one of the steps. This prevents the envelopes from being gated by the corresponding step. The sequencer can certainly provide great possibilities for cool sounds!

Finally, the back panel contains the ports, which include a USB port, MIDI In, Out/Thru, Poly Chain (for connecting more DSI instruments to expand polyphony), Sustain pedal, Expression pedal/CV input, and a headphone jack.


3.5 Stars

Overall, DSI has done a great job of finding the sweet spot between compactness and usability. While the Mopho x4 may have a different layout than some are used to (i.e., the modulation wheel and pitch bend wheel are ABOVE the left-most keys, instead of next to them, as a space-saving measure), we didn’t find these changes overly impactful in actual use. Certainly, on a larger synth, like a Prophet 12, you might get dedicated knobs for each LFO, whereas on the Mopho x4 there’s one set of knobs and a single button to toggle between the LFOs. Much of the Mopho x4’s parameters are set up this way: one set of knobs, and then a button to toggle which voice, LFO, etc., they control. For regular use, this shouldn’t be too big a deal, but if someone absolutely has to turn knobs simultaneously on LFO 1 and LFO 3, they may be disappointed with the Mopho x4. Unlikely this scenario will happen too often, though!

Programming the sequencer took a little getting used to, but just because the hardware interface is somewhat compact, there’s no need to worry. To help with programming and editing, and “seeing it all at once,” SoundTower provides editor software to use with the Mopho x4. We have had positive experiences with SoundTower software in the past (using their Korg editor), and the Soundtower editor for the Mopho x4 functioned just fine, and made an easier task of sequencing.

Outside of the software, the Mopho x4 was easy to work with. All components felt solidly built, and while small by todays’ touchscreen standards, the LED screen gave enough information to let you know what was going on.

As with other DSI synths, there’s a “Push it!” button, and that we did. The button can be particularly helpful while programming a sequence: it will trigger the sequence, so you can hear your tweaking in real time, while you’re designing the sequence. It’s little things like this that make a big difference in your forward momentum while working on sound design, particularly when you have a smaller footprint box like the Mopho x4. Even so, programming the sequencer is probably the area where the software will be most helpful, as opposed to fiddling with buttons on the hardware.


4 Stars

It’s a DSI synth… need we say more? It sounds great! These sounds definitely have a bit of an edge to them—in a good way. While you can certainly get nice, lush pads, the more aggressive sounds really excited us. Perhaps this is, in part, due to the two sub-oscillators that even the Prophet 8 lacks. While there’s clearly a lineage, the Mopho x4 does have its own character.

The presets are all very good, too, and while some are evocative of ‘70s and ‘80s sounds (i.e., presets Tom Sawyer, Tron Cycle, 2600 Twitter, to name just a few), there are a lot of other sounds that fit easily in today’s modern world. And, the Mopho x4 can deliver a moody vibe if you’re after something dark and brooding. Here is a brief example using the “Universe” preset. (Insert MP3 LINK H ERE!).

Not surprisingly, Dave Smith loves his own creations. There is a good video featuring Dave himself demonstrating some of the Mopho x4 features and sounds on the DSI website at this link.

Additionally, a second video features a pretty cool performance by Peter Dyer using the Mopho x4. These two videos do a great job really showing off preceisely what the Mopho x4 is all about.

All in all, great stuff worthy of any studio seeking some classic DSI analog sounds at a bargain price.


Documentation and Product Support

4 Stars

The Mopho x4 actually comes with a manual! While it is short compared to the frequently-too-long-and-way-too-complex volumes from Japanese synth builders, the manual is quite clear, to the point, and makes things easy to understand. In fact, the manual saved us a few emails and phone calls to DSI that we would have otherwise needed to make if this keyboard were someone else’s product. We don’t say that very often! As mentioned, there’s also videos of Dave himself on the DSI website to explain things too.


3.5 Stars

The DSI Mopho x4 (MSRP $1,429) sells for $1,299 street. While it only offers four voices (to start), you get a true analog synth with all the benefits of modern technology (stable oscillators, USB, etc.). And, it sounds great!

The Prohpet 12 sells for over $3,000, so the Mopho x4 is a great way to get into DSI’s sound on a smaller budget. When you’re ready to grow, you can Poly Chain another DSI synth to add additional voices. If you’re looking for a great sounding, portable analog synth with modern features, you should be putting the Mopho x4 at the top of your list to check out.

Contact Information

Dave Smith Instruments

Overall Rating - Product Summary

Category Value Rating
Features 20% 3.5 Stars
Usability 25% 3.5 Stars
Sound 25% 4 stars
Documentation & Support 10% 4 Stars
Price 20% 3.5 Stars

OVERALL RATING = 3.7, which earns it a WIHO Award!

3.6 stars or better: Outstanding, WIHO Award
3 stars or better: Worth considering
2 stars or better: Suited to specific needs
1 star or less: Not recommended
  Evaluation Short-List
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