U-HE ACE Monster Analog Sound from a Soft Synth

I’m a big fan of Zebra, U-he’s flagship softsynth. When I heard about ACE, I thought, “Oh, that’s cute — a strippeddown little brother for Zebra.” Boy, was I wrong. ACE may have a modest price and a modest list of modules, but its sound palette is very broad, and the sound itself is satisfyingly rich and “vintage.”
Publish date:
Social count:
I’m a big fan of Zebra, U-he’s flagship softsynth. When I heard about ACE, I thought, “Oh, that’s cute — a strippeddown little brother for Zebra.” Boy, was I wrong. ACE may have a modest price and a modest list of modules, but its sound palette is very broad, and the sound itself is satisfyingly rich and “vintage.”
Image placeholder title
0510 U-He Ace Main


  1. Tuning, glide, pitchbend depth, and other global parameters are here.
  2. The dual LFOs go into the audio range, and can be used as extra oscillators.
  3. Oscillator 2 can be soft-synced or cross-modulated.
  4. The mixer has three modulation inputs for hardwired signals, plus an extra signal input at the bottom.
  5. Each filter has both lowpass and highpass/bandpass/ notch outputs.
  6. These “mults” are for mixing signals and modulating their depth.
  7. The ADSR envelopes can treat the sustain portion as a rising or falling slope, with adjustable rate.
  8. Panning can be modulated in the dual output modules.
  9. Here’s where you patch in modulation sources such as breath control and aftertouch.

I’m a big fan of Zebra, U-he’s flagship softsynth. When I heard about ACE, I thought, “Oh, that’s cute — a stripped-down little brother for Zebra.” Boy, was I wrong. ACE may have a modest price and a modest list of modules, but its sound palette is very broad, and the sound itself is satisfyingly rich and “vintage.”

ACE’s design is very loosely based on the fabled ARP 2600. It has a fixed set of modules, all of which are immediately visible on the panel. These are “normalled” to one another for easy sound programming — if you don’t do anything with virtual patch cords, you get a familiar oscillator-to-filterto- envelope signal flow. Like the 2600, ACE also has numerous patch points. You can interrupt the normalled signal path with any other signal you choose, simply by dragging a patch cord from an output to an input with the mouse.

What sets ACE apart, though, isn’t just the patching. Most digital and software synthesizers use control signals (such as the output of an LFO or envelope generator) that run at a fraction of the audio sampling rate. This saves on CPU power. In ACE, everything runs at twice the sampling rate of your host DAW. The downside: ACE is something of a CPU hog. The benefit: You can jam an LFO up into the audio range and use it as a third oscillator, or use it to frequency- or amplitude-modulate one of the other oscillators or a filter. Hence the acronym: ACE stands for Any Cable Everywhere.


Installing ACE on my new Windows 7 computer was painless, and it ran without problems in both Steinberg Cubase 5 and Image-Line FL Studio 9. The factory presets, created by well-known sound designers Howard Scarr, Skippy Lehmkuhl, and others, are plentiful, varied, and high-quality. Basses, leads, keys, pads, chord stabs, rhythm patterns, analog percussion, modular madness — everything is neatly categorized in the browser, which also has a display pane for the patch creator’s performance notes.

Learning my way around the ACE panel took a couple of hours. The jacks aren’t labelled, so I made a couple of wrong assumptions — but also, the number of ways to patch things together is vast! Getting buzzy, grinding tones is easy, but I’ll need a lot more time to explore the full range of possibilities.

ACE has a four-position switch for “quality” (presumably the internal sampling rate). A “draft” rate saves on CPU cycles, but may sound audibly thinner or have aliasing. Three knobs you don’t usually see are for slop, crosstalk, and even simulated capacitor failure in the oscillators. These all add to the analog instability of the tone (and yes, like ACE’s other knobs, they respond to MIDI control). These knobs are on a second panel, called Tweak (click on image below). This panel is also where the mapping generator lives — see the “Mapper” section below.

0510 U-he ACE tweak

For fat sounds, up to eight voices can be stacked and detuned to produce chorusing or one-finger chords. (The voices can’t be panned separately, however.) On my system, using more than four voices sometimes caused the signal to suffer a short delay or breakup during its initial attack, even with a very simple patch — but since you can produce 16-note chords with four voices, this is not a big problem.

ACE has two glide controls: VCO1 and VCF1 can glide at a different rate from VCO2 and VCF2. With patches that use oscillator sync or filter overdrive, this can add some nice bite to the attacks of notes that are more than a whole-step apart, as the two oscillators will be sounding different pitches for a brief moment. Also available is an ARP-style duophonic keyboard mode, in which VCO1 tracks the lowest note you play and VCO2 the highest note. Duophonic mode opens up some unusual possibilities, especially if VCO2 is soft-synced.

The factory presets (several hundred of them) are incredibly varied. A couple of one-finger chord patches turned into riffs, which quickly became the basis of a new piece that I’m planning to include on an upcoming CD.


If you’ve ever patched an analog synthesizer, you’ll understand the basics of sound design with ACE, and we’re not going to explain filter cutoff or ADSR envelopes in this review. But ACE gives patching a few fresh twists.

A glance at the panel seems to show two LFOs and two VCOs (tone oscillators), but that’s a misleading impression. In fact, the LFOs are full-range audio oscillators, so what you’re really looking at are four oscillators, each of which has different controls. They have five frequency modes — semitone, partial, subharmonic, Hertz, and clock sync. In the first three modes, they track the keyboard. These modes interact with an unusually flexible fine-tune knob, which has four modes — multiply, cents, 5Hz, and beats. (Multiply mode can trip you up, because you can set it to zero, which will turn the oscillator off.) There’s also a suboscillator, which always tracks the frequency of VCO1.

VCO2 can sync to VCO1 or be crossmodulated or ring-modulated by it — or all three at once, in varying amounts. Analogsounding soft sync is produced when the sync knob is turned up only part way. While looking for a lead tone for a new piece, I was twiddling these controls and stumbled onto some overtones that were quite violinlike. Nobody would mistake the patch for a real violin, but it has a similar character. I did it by soft-syncing VCO2 to VCO1 at about 45%, setting the VCO2 coarse tune knob to partial mode, and dialing the partial up to about 7.6. These controls are quite sensitive to small changes, so finding this tone was a happy accident.

LFO1 has only one waveform (sine), but it also has an input for sample-andhold effects. LFO2 has five waveforms. The LFOs can run in gate mode, in which each new note starts its own LFO at a point determined by the phase knob, or in free-run mode, in which all voices share one LFO.

Not enough LFOs to suit you? Use the ramp generator. This has no inputs or waveform selections, but it can either loop, producing a repeating waveshape, or trigger once and then stop to produce an attack transient. Its up, hold, and down knobs can sync to quarter-notes or whole-notes — or to decimal fractions thereof, so if you need, say, a five-against-four cross-rhythm, just set a knob to 20 and you’re in business. This feature is also available with LFO rates.

The filters each have two simultaneous outputs. One output gives you a choice of four lowpass modes (singlepole through four-pole), while the other has a choice of highpass, bandpass, or notch. The filters can be overdriven at the input with a gain knob. They can self-oscillate and be modulated by audio-rate signals for rich Minimoogstyle sidebands.

The envelopes are basic ADSRs, not multi-segment types, but each of them has four input knobs, two each for time and level control. The fall/rise knob turns the sustain “level” into a rising or falling slope. (Due to limited panel space, the fall/rise rate knob is in the ADSR, while the fall/rise amount is tucked away on the Tweak page.) Envelope output can be controlled via velocity. In addition, knobs for level and rate control can accept inputs from various MIDI sources.

Near the bottom of the panel are two multiples. In a hardware synth, these would often be needed to split a signal to several outputs, but ACE can stack multiple patch cords on any output. The multiples are used to mix signals before sending them to inputs, and also to modulate their amounts in various ways, including crossfading.

The row of output jacks along the bottom gives quick access to ten useful signals, including MIDI key number, velocity, noise, mod wheel, and aftertouch. At the other end of the signal chain, ACE has dual output VCAs, which can be panned separately.

The animated waveform display is a toy, but it’s well-designed: It attempts to sync to the fundamental of the waveform, making it easier to watch the dancing squiggles. More practical is that the numerical value of each edit is shown in the display, and you can move in finer increments by shift-dragging.


ACE has one extremely useful module whose concept is, frankly, digital. The mapping generator (see Figure 1 above) can be a keyboard zone mapper or a primitive step sequencer, among other things.

The mapper provides up to 128 userdefinable steps, which are edited graphically on a nice big display. It operates in one of four modes. In Alternate mode, it moves to a new step each time you press a key. In Key mode, each MIDI key selects a step in the mapper, which means you can have a different output level from each key on the keyboard if desired. In Map Smooth and Map Quantize modes, it accepts a signal input and maps the level of this signal onto an output in either smooth or stepped fashion. This is useful for setting up a nonlinear velocity response curve, for creating a stepped output from an LFO, and so on. Utility commands let the data in the mapper be randomized or quantized to clamp it to a certain number of discrete values (four or eight, for instance).

When the input is a repeating signal from the ramp generator, the stepped output produces a regular rhythm pattern, useful for step sequencing. The mapper’s output can also be used as a waveform for LFO 2.


There are two main reasons to like ACE: It’s highly patchable, and it sounds very analog. Make that three — there’s the very modest price. Patching with cords (even when you do it with a mouse) is much more fun than dialing up values in a number-filled matrix. While the panel looks simple, with everything plainly visible on the surface, the voice design is packed with unusual options — and yet they’re easier to understand and deal with than in some of the extremely feature- rich soft synths I’ve looked at, because the signal routing is always visually obvious.

For anyone who learned synthesis on the ARP 2600, programming ACE will be addictive. I had trouble tearing myself away from it long enough to finish writing this review — and for all the huge sound it gives you for such a low price, it’s certainly a Key Buy.

PROS Surprisingly deep sound programming. Great factory presets. “Real analog” tone.


CONS Needs a fast CPU.

INFO $85, u-he.com

CLICK HERE for an originial synth violin piece author Jim Aikin created in U-he ACE.


What types of synthesis does it do? Modeled analog, including FM and AM.
Most unusual features? Audio-rate modulation, mapping generator, oscillator soft sync, duophonic keyboard response, dual glide mode.
How are the effects? They’re basic: You get a chorus/phaser, synced delay line, and treble/bass EQ.
Do you get pulse width modulation or oscillator sync? Yes and yes.
How about microtunings? ACE loads Scala files for highly flexible custom tunings.
Formats and computer stuff: VST, AU, and RTAS. Windows or Mac OS 10.4 or later. Intel Core2 Duo or better processor recommended.
Copy protection: Serial number entry.
Downloadable demo? Yes.