UDO Audio Super Gemini

If you thought the age of hugely ambitious polysynths was over, think again...

“20‑Voice Dual Layer Polyphonic Binaural Analog‑Hybrid with Super Wave Technology” is quite a description. But the Super Gemini has big ambitions. It aims — and mostly succeeds — in standing shoulder to shoulder with synth giants like the Roland Jupiter‑8 and the Yamaha CS‑80.

UDO are still relatively new to the synthesizer world. In late 2021, they released their first product, the Super 6. Inspired by the Roland Jupiter‑6, the Super 6 takes the six‑voice polysynth concept to new heights with a true‑stereo signal path and FPGA digital oscillators capable of alias‑free audio‑rate modulation. Like its principal influence, the Super 6 offers a hugely tactile user experience, with physical controls for nearly every parameter.

The Super Gemini takes the Super 6 and doubles it. You get two layers of the Super 6 engine, known as the Upper and Lower layers. True to UDO’s desire to keep things tactile, each layer has a complete set of duplicate controls on the front panel. The Upper layer has white fader caps, whilst the Lower layer uses a fetching orange. Of course, that’s not the end of it. UDO have added plenty of additional features to harness the extra power.

It’s A Beast

The instant reaction to the Super Gemini is, “Whoa, it’s big.” At 1040 × 440 × 110mm, it will be one of the larger keyboard synthesizers in any rack. While there are plenty of five‑octave keyboards in the synth world, it’s the depth that adds extra size, and that’s because of the dual set of Super 6 controls for each layer and the new ribbon controller. The keyboard supports poly aftertouch, too, which is a lovely addition.

The overall build quality is superb. It’s a beautiful design, whatever angle you look at it from. The white, grey and orange colour scheme is right up my street. I’m also glad to see that the overhanging keys from the Super 6 have gone. They could prove a roadie’s nightmare.

Round the back is a nicely recessed panel for the various connections, including stereo mix outputs, stereo upper and lower layer outputs, MIDI In, Out and Thru, a USB Type‑B connector for MIDI and file management, and four pedal/CV inputs for sustain, expression, volume and delay freeze (more on that later).

Round the back we find everything you’d hope to find on a large polysynth like this: an IEC mains cable input for the built‑in power supply, full‑size MIDI In, Out and Thru ports, a USB B port, quarter‑inch jack sockets for the four(!) pedal inputs, a stereo mix output and separate stereo outputs for each layer.

Super Twins

As briefly as we can, let’s recap the Super 6, because each layer of the Super Gemini is essentially a Super 6 with tweaks. I reviewed the Super 6 in the December 2020 issue and won’t go into the finer points here, so I refer you to that original review if you want the full details.

The Super 6 synth architecture comprises two ‘DDS’ (Direct Digital Synthesis) oscillators, two filters, two envelopes, two LFOs, a delay, a chorus, an arpeggiator and a sequencer, all doubled on the Super Gemini. Probably the most significant Super 6 feature is Binaural mode. When engaged, the entire synth works in true stereo, with the signal path — oscillator, filter, amp and effects — having duplicate voices for each stereo channel. In the Super Gemini, each layer can be switched to Binaural mode independently, which is true of most features, as the two layers are independent.

Binaural mode halves the number of voices available, but creates some superb sounds. The Super Gemini can generate 20 mono voices or 10 Binaural voices. So, when using it in Dual or Split mode, you’ll get five voices per layer, one less than the Super 6.

Oscillators

The first oscillator — DDS1 — can operate in Super mode, which offers seven unison copies of either standard analogue‑type wave shapes or one of 16 single‑cycle waveforms. The second oscillator — DDS2 — cannot do unison or single‑cycle waveforms, but offers pulse‑width modulation on its square waveform and a selection of more normal analogue shapes. It can also double up as an LFO, or as a sub‑oscillator phase‑locked an octave below oscillator one.

DDS1 is where we find the first of the Super Gemini’s audio engine upgrades: wave morphing. You can assign any of the 16 waveforms to Wave A and B, and then morph between them. The Super 6, by contrast, can only play back a single static waveform. Morphing can be automated using LFOs or envelopes, and is available as a modulation destination in the matrix. This is a significant update to the oscillator. It’s a shame it’s not a full wavetable, but it’s welcome nonetheless.

A ‘DSS Modulator’ section offers a wealth of oscillator modulation options, including controls for DSS1’s Super mode, dedicated controls for LFO and envelope pitch modulation, and the fantastic Cross Mod, which uses DDS2 to frequency‑modulate DDS1. In my original Super 6 review, I did remark that the pitch of DDS1 will move as more cross‑modulation is applied, which means that patches could be out of tune with no way to correct them. This is because Cross Mod uses exponential FM, which changes the pitch of the carrier wave. I’m pleased to see two new ways to retune on the Super Gemini. The Lower Layer has a dedicated Detune control to detune the entire layer relative to the Upper Layer, and a Performance preset also has a Detune option. So, if you’re doing static cross‑modulation, you can retune quite easily.

Other ways to cross‑modulate the oscillators are hard sync and ring modulation. The latter is also new to the Super Gemini and is an excellent addition, especially if you want to recreate classic synth sounds. The vast potential when combining cross‑mod, sync, unison and ring mod is not to be underestimated.

Filters

The filters are an analogue, low‑pass, 24dB‑per‑octave SSI design based on the classic SSM2044 chip used in the PPG Wave 2.3. They have a lovely resonant character, although some bottom end is lost when adding resonance. This can be mitigated somewhat with the filter drive setting. It’s also possible to apply frequency modulation to the filter from DDS2, and it sounds fantastic.

No flagship synth would be complete without a high‑pass filter, and it’s nice to see that, unlike the simple three‑position switch that controls the high‑pass filter on the Super 6, the Super Gemini has a slider for full, variable control. It’s a shame they didn’t make it resonant, but it’s definitely an improvement.

Amp & Effects

The amplifier section is reasonably straightforward, with dedicated controls for level, envelope routing, and velocity (just three positions: off, half and full), plus LFO1 and DDS2 modulation. The DDS2 modulation control is new to the Super Gemini and opens up the amplifier to audio‑rate modulation, which is an exciting addition. Envelope 2 is the standard amp envelope, but it can be switched to a simple gated mode or a gated mode with a more prolonged release, which frees up the second envelope for other duties.

Each layer has a Juno‑style chorus effect, stackable I and II buttons for three different chorus strengths, and a BBD‑like delay. I had lots of fun with the two layers of delay. I’m glad UDO didn’t skimp by making the effects global.

Modulation

UDO’s approach to modulation is to offer plenty of controls on the panel for the everyday stuff. For example, there are sliders for LFO and Envelope control of oscillator pitch, filter frequency and amplitude. There is also a mildly intimidating modulation section above the combined pitch wheel and modulation stick. Here, you can assign LFO2 for vibrato and tremolo. LFO2 and the various aftertouch, portamento and modulation‑stick settings are common to both layers, although you can choose to have them affect either or both layers as you wish.

A quick note on the pitch‑bend stick, while I mention it. In my review of the Super 6, I expressed some concern about the feel of the pitch stick, particularly when pushing it upwards to apply modulation. It felt very stiff, and was hard to use without the pitch stick flying to the left and applying unintentional pitch‑bend. This could have been an anomaly on the unit I was sent, but it was enough of an issue that I mentioned it in the review. The good news is that the Super Gemini pitch stick feels much more responsive, and I haven’t experienced the same problems.

For more unusual modulation requirements, each layer has a modulation matrix. Because of the Super Gemini’s lack of a screen, this uses the 16 buttons usually used for patch selection. Eight buttons on the left are sources — DDS2, LFO2, envelope 1, velocity, aftertouch, expression pedal, ribbon and key tracking — and the eight on the right are destinations: LFO 1 speed, cross‑modulation, wave morph, oscillator mix, high‑pass filter, low‑pass resonance, envelope decay and delay time. If you don’t see your favourite destination listed, don’t worry; you can assign to other destinations by wiggling a control. Using the modulation matrix is easy: choose a source and a destination and then adjust the amount knob located next to the 16 buttons.

The modulation matrix is a little different to that of the Super 6. UDO have tweaked the list of available sources and destinations. The obvious example is the addition of the ribbon as a source, and rightfully so. The ribbon is a fantastic source of expression, and its inclusion means you can make the most of it in your sound design. It comes at the expense of the Bend+ and Bend‑ sources on the Super 6, which is a clever switch. You use the ribbon controller instead of the pitch‑bender, which will still work for basic pitch‑bending. And because they removed two sources and replaced them with one, it made room for the key‑tracking modulation source, which doesn’t exist on the Super 6.

The list of destinations has changed, too. Gone are the Envelope 2 release, LFO 1 phase, and delay feedback options, to be replaced by waveform morph, oscillator mix and high‑pass filter. These replacements matter far less, because you can always assign one of the eight sources to destinations that are not available on the buttons by wiggling the knob or slider you wish to modulate. So, the envelope release, LFO 1 phase, and delay feedback are still options, even though they’re not on the buttons any more.

The ribbon controller and the keyboard’s poly aftertouch capability are solid additions. By default, the ribbon controller is assigned to pitch, but when you apply something else, the pitch modulation is removed, allowing you to assign it to as many destinations as you wish. I only wish there was a mode where the amount of modulation would ‘stick’ when you remove your finger from the ribbon. I found the default behaviour of snapping back to zero when disengaging from the ribbon wasn’t always what I wanted. Still, it’s a great performance tool.

The Super Gemini is big, but what do you expect with two of everything plus a ribbon controller, arpeggiator, sequencer, and so on? It measures 1040 x 440 x 110mm and weighs in at a healthy 14.5kg.

Double Dip

Dealing with Super Gemini’s dual layers is easier than you might imagine. The keyboard can work in three modes: Single, Dual and Split. Single mode plays just one layer, giving you 10 voices in Binaural mode or 20 in mono mode. You can use either layer for this mode, switching between them with the layer select buttons. I thought this would be useful for live performances where, for example, you switch between two sounds for the verse and chorus of a song. Sadly, any release stage or delay echo still audible is abruptly cut off when switching, making it less useful in this scenario.

Dual mode stacks the two layers on top of each other. This is your mode for epic layered, detuned, complex patches. It is, in almost all aspects, like having two Super 6s playing at the same time. The Lower layer has a dedicated Detune knob to retune it (±7 semitones) relative to the Upper layer. The 20 voices are split evenly between the two layers, and with Binaural mode enabled, that means five voices per layer.

Lastly, there is Split mode, where you play the Lower layer with your left hand and the Upper layer with your right. You can move the split point anywhere on the keyboard. Like dual mode, the voices are split evenly between the two layers — 10 in mono and five in Binaural mode.

The Super Gemini has two preset types: Patches and Performances. A Patch is a single‑layer sound, whereas a Performance saves both layers plus any relevant configuration settings. It’s easy to switch between loading either type, and if you’re loading Patches, you load into whichever layer is currently selected. I appreciate the simplicity of this. Once a Patch has been loaded into a Performance, it is independent of the original. So you can alter or save over a Patch without the danger of affecting any Performances that the Patch was loaded into.

There are 128 Performance slots and 128 Patch slots to save your sounds. By today’s standards, it’s a slim number. You won’t be buying multiple preset packs from the Internet and storing them all on the machine. You can use the USB connection to mount the internal drive on your computer and transfer sounds as needed, but I feel that would get annoying. Also, because there is no screen on the Super Gemini, there is no patch naming. You have to remember that your favourite sound is in Performance Bank B, slot 4C. This is the one area where I feel UDO could have compromised on their old‑school vision. A tiny OLED screen for patch naming would not detract from the hands‑on methodology. At the same time, I admire their steadfastness in avoiding that slippery slope.

Pedals

The Super Gemini is generous with its pedal inputs. There are four inputs on the rear: sustain (with auto polarity detection), expression (TRS), sustain (TRS) and delay freeze. The expression pedal is freely assignable in the modulation matrix, and the volume and sustain pedals work as you’d expect and are assignable to either layer. You can even use a dual sustain pedal to control the two layers independently.

The delay freeze input is fun. Connect a single or dual footswitch, and when engaged, the delay feedback will increase to 100 percent while the delay send is reduced to zero. This causes the delay buffer to loop endlessly and allows you to play over the loop. This is commonly known as a ‘sound‑on‑sound’ loop: a fine name if ever I heard one!

Conclusion

Let’s talk about the most crucial aspect of any synth: its sound. In my review of the Super 6, I summarised its character as “classy”. The Super Gemini is no different. The sound matches the build quality. It’s refined, spacious, detailed, rarely harsh (unless deliberately so) and highly likeable. The Super Gemini can easily conjure Vangelis‑style space leads, faux electric pianos, ambient pads, ’50s sci‑fi soundtracks, Juno basses, ’90s rave stabs, classic brass pads, or ’80s pop synths. I could go on. What’s impressive is just how well it does any of these. Close your eyes, and you could be listening to a Juno‑60, a CS‑80, a Jupiter‑8 or any classic analogue polysynth.

Whereas the Super 6 was inspired by the Roland Jupiter 6, the Super Gemini feels like a descendant of the Jupiter 8, with a bit of Yamaha CS‑80 thrown in. Regarding the sound, I won’t compare it directly to old synths because the Super Gemini has its own thing going on. Still, it shares the refined, sometimes grandiose power those machines are famous for.

So, the Super Gemini is an evolution of the Super 6. The base character is very similar. There’s just more of it. I suspect many people reading this review will wonder which is right for them. I don’t think the little extras like ring modulation, variable high‑pass filtering, wave morphing or dedicated delay freeze input would sway anyone to pay extra for the Super Gemini. But the dual layers, poly aftertouch and ribbon controller might.

Having two Super 6 layers at your disposal feels luxurious. There are many ways to use the extra power that the Super Gemini bestows. You might craft a beautiful pad sound on the upper layer, then use the lower layer to sprinkle over a subtle arpeggio or noise that pans around the stereo spectrum. Or, you might use one layer in Single mode to get extra polyphony (10 voices in Binaural mode or 20 with it disabled). Or sequence the Super Gemini from a DAW, for two independent synth sounds with separate outboard processing. Indeed, for anyone who wishes they had a second Super 6, the Super Gemini is an ideal solution.

One of UDO’s top priorities is clearly the playability of their instruments. In this endeavour, the Super Gemini does not disappoint. Poly aftertouch, the ribbon, the delay freeze pedal input and the ability to split layers on the keyboard add a wealth of performance options the Super 6 cannot do. If you are a keyboard player, first and foremost, the Super Gemini should be high on your list.

My only real disappointment with the Super Gemini is the decision to reduce the number of voices from the Super 6. “But 20 voices is more than 12!” I hear you protest. And you’re right, of course. But two Super 6s would give you 24 voices in total, or 12 in Binaural mode. The Super Gemini has 20 voices, or 10 in Binaural mode. So, if you use Dual mode and Binaural mode together, you are limited to five‑note chords, which feels a bit limited. If we’re being picky, the Super Gemini is two ‘Super 5s’. But, in reality, it rarely matters. Almost every analogue polysynth has voice trade‑offs, and the Super Gemini is more flexible than most. Binaural mode isn’t always needed; without it, you double that five‑voice polyphony, which is enough for almost any combination of sound and playing style.

The Super Gemini is a big, beautiful instrument. Everyone who has entered my studio since it’s been here has commented on its good looks, quickly followed by equal admiration for its sound.

The Super Gemini is a big, beautiful instrument. Everyone who has entered my studio since it’s been here has commented on its good looks and admired its sound. It’s a treat to look at and a treat to play. The keybed, the new ribbon, and the consistent tactile feel of every knob and slider all add up to a very classy ‘under the fingers’ experience.

The Super Gemini is an impressive addition to UDO’s line‑up and is far more than just two Super 6s sandwiched together. It’s always a pleasure when manufacturers release a big flagship instrument. From a business perspective, it’s a brave and financially risky thing to do. I wish UDO every success with the Super Gemini. It deserves to do well.