Review – ACE by u-he

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ACE is a powerful, semi-modular synth plugin that’s easy to learn, has many useful features, and is very flexible. We take it for a test ride in this review.


by Rob Mitchell, May 2015


The music software company u-he has released some exceptional products over the years. They have won multiple awards (and might I say, deservedly so), and are highly acclaimed on many music forums. In my opinion, Zebra 2 and Diva are two of the top synthesizer plugins on the market today. In our previous issue, we presented a review of Diva. For this review, I will be going over their semi-modular synthesizer plugin called ACE. 

ACE has the ability to virtually patch any output to any of its inputs. The plugin’s name is actually an acronym that describes that same functionality: Any Cable Everywhere. It uses virtual cables to accomplish this, but it can be used immediately without the cables, too. It is hardwired with a default routing behind the scenes, so you can get sounds out of it right away. Of course, that’s much less flexible and definitely not as much fun. What’s the point of getting a plugin like this if you don’t patch it together?

It is a plugin which reminds me of the great hardware synthesizers from the past. It can be just as powerful, and with a price that is minuscule compared to modular hardware synthesizers. Have you ever looked on EBay and checked what some of those classics are priced at? I saw one such hardware synth that sold there for over $10,000 USD.


Installation and Requirements

The latest version of ACE can be downloaded from the u-he website for installation.  Initially it is a demo version, but it becomes fully functional after you enter the license information. During the install, you are asked which versions you’d like to have installed (VST2, VST3, AAX, etc.) and where it should be located on the computer’s drive.

ACE is demanding on the CPU, and this is clearly stated on their website. As long as you have a modern computer, you should be OK. You can always try out the demo version on your system to see how it runs.  

The system requirements are as follows: A modern PC or Mac, multicore CPU with SSE2, and one gigabyte (or more) of RAM. For the PC you’ll need a Windows XP or higher operating system, and for the Mac, you’ll need an OS X 10.5 or higher operating system. ACE supports 32-bit and 64-bit for all formats.


Now Hear This

When you first get it registered and running, you might just want to check out some of the presets to hear what it can do. The first preset that is loaded by default is an initialized preset. This is basically a blank slate to get you started on making your own presets.

At the top of the display is the name of the preset, and arrows on either side of it to scroll through the others. You can also just click the “Patch” button in the upper left to see the full browser. The categories of presets are along the left side of the browser, and the presets themselves are displayed in the middle. There is an area on the right side for any notes the preset’s author has for the preset that is loaded.

In the browser, if you right-click on a preset, you’re able to mark it as either a Favorite or as Junk. If you mark it as a Favorite, it will put a star next to its name. When it’s marked as Junk, it disappears from the list of presets. You can always retrieve a junked preset by right-clicking in the browser, and then you just have to click on “Show Junk”. I thought most of the presets were really very good, so I don’t think I would use the “Junk” option very often, but it is handy to have that functionality built-in.

At first, I had tried out ACE on my older PC which has a dual-core CPU. It was having some issues trying to play some of the presets, mainly a bit of crackling and some dropouts. In all fairness, many of the simpler presets would play back satisfactorily. When I tried to use more than one instance in my DAW however, it was really just too much for it. In general, that aging PC just wasn’t up to the task of handling this powerful synth plugin.

One thing u-he mentions in the manual is to not use the “Multicore” option on computers with older processors. They also state that the Multicore setting will work much better with an i5 or i7. Just to see what would happen on my older dual-core PC, I enabled the Multicore option in the upper-right of the display. Lo and behold, it was just like they said; it did not work well. More often than not, it would crackle and break up the sound. It actually worked much better with Multicore switched off, though it was still struggling with some presets, as I mentioned before.

If you really have no other choice but to use an older PC, try leaving the Multicore turned off, and you may want to lower the included quality settings which are located in the upper-left. ACE has Draft, Standard, Good, and Accurate settings, with Draft being the lowest quality (but isn’t too bad really), and Accurate being the highest.

Recently I acquired an Intel i5-based laptop. It has Windows 7 (64-bit) installed and six gigabytes of RAM. I have ACE loaded up in Sonar X3 to check it out for this review. Let’s go check out some of the features in ACE, and see what it can do.



Among the many modules that are included in ACE, among the most important are the oscillator and filter modules. The two oscillator modules are the main sound sources.  They have a frequency range of 0 to 20 kHz.  Actually, the LFOs can be used like the regular oscillators as well, but I will get into that later.

The waveform blend control lets you adjust from a sawtooth to a pulse wave (the control being the upper row, third from the left).  The tuning mode control is the one in the upper left corner (labelled “partial” in the image).  There are five modes: semi, partial, subhrm, hertz and sync.  They are somewhat explained in the manual … including one instruction to the reader to look up “Trautonium” on the web.  We’ll leave a deeper understanding of the mode as an exercise for the reader. 

Next to the waveform blend control is the pulse width control, which lets you adjust the PWM amount from 0-100%. You are able to use any signal to modulate the pulse width, or you can just use LFO2, which is hardwired to it. The amount of modulation (from whichever source) is adjusted by using the knob right below the pulse width control.

To use a different module for PWM, you just connect a cable from the module’s output you want to use, and then click on the input below the LFO2 level control, and adjust its level for PWM as needed. This is just one simple example of the way you can connect the modules together. When “Reset” is enabled, the oscillator will have a fixed phase, and if it is not switched on, it will be free running. 

The first oscillator (VCO1) can also use a peak/triangle waveform, and a 3-mode sub-oscillator. To change to the peak/triangle, just click the label below the waveform blend control. The second oscillator (VCO2) can be ring modulated by VCO1. It can also be synced with VCO1 and cross-modulated as well.

The Mixer section is where you adjust the levels of the oscillators. You’re able to change the balance between VCO1 and VCO2, and adjust the level for the sub-oscillator. There is a noise generator located here too, and it outputs white noise. They’ve also included an Auxiliary section with its own input that you can use however you want. In addition to the balance and volume controls in this section, there’s a Mixer output jack you can use, and all of the other individual controls have their own modulation inputs.



ACE has two filters which allow you to contour the sound the way you want. Each of them has four types of low pass filters, and there are high pass, band pass, and band reject filter types included. Using the virtual cables provided, the filters can be self-oscillated. Also, the manual mentions running the two filters in series, and this can give you a good amount of serious distortion.

They’ve included a Gain control, which has both negative and positive values (bipolar). Cranking up this control can get you an overdriven/distorted type of sound. When this is used on a sawtooth, it morphs into something similar to a pulse wave shape. The filters also have standard cutoff and resonance controls, and a key-follow control.

There are two cutoff modulation amount controls. The first one is hardwired to the ADSR2, and the second one is connected to LFO2. Like most everything in ACE, you can bypass their configurations, and hook them up to just about anything else that you could want.

The filters really sound impressive and work well even if they are overdriven. If the gain is cranked up, or you have them connected in a serial manner (I mentioned this earlier), there is still room left to manipulate the resonance amount with no problem.


LFOs and Envelopes

I briefly started to mention this earlier, but wanted to detail it a bit more here: One very cool thing about ACE is that the LFOs have the same tuning options as the main oscillators, so they can be used as audio oscillators themselves.

Using the Phase control, you can adjust the phase location of the waveform when it’s reset. It can also be used for PM (Phase Modulation) as it has an input for just that. You could connect another oscillator to that input, or use the LFO itself for modulation. This will give you those famous FM sounds, which really used PM, and not FM/frequency modulation.

LFO1 uses a pure sine wave, but LFO2 has more waveforms to choose from. These include a sine (like LFO1), as well as a triangle, square, sawtooth, and one setting they call “Tap Map”. This lets you use the Mapping Generator as a waveform source within LFO2. I mention more about the Mapping Generator later in this review.   

ACE has two ADSR envelopes, and each of them has an output jack. They use sliders to control the amount for each stage of the envelope, and the Fall/Rise control will let you set the sustain stage so it will fall or rise at a certain rate. Rate modulation can be assigned how you’d like, and it can be controlled with its amount knob. Modulation of the velocity level works in much the same way. The Snap mode lets you get a bit more of an edge to the decay and release stages, making them more “snappy”.

The Ramp Generator is an AHD (attack/hold/decay), which can be used as another type of envelope. It has a few tricks up its sleeve you can use. One way to use it is with its “Rest” setting at its maximum setting, and it will then act as a one-shot envelope. It can also be used with “ramp clock” which is a parameter you can use on the Tweak page. I’ll get to more detail for that page in the next section.


Tweak Page

To get to ACE’s Tweak page, just click the “Tweak” button in the upper left. This is where you can use what is called the Mapping Generator. It includes three different modes to change the way a source will work with its mapping. A couple of ways the maps can be used are to make patterns to affect things like the oscillator tuning, or the cutoff amount.

You’re able to draw/edit the pattern that is in the window to your liking. Using a right-click in the edit window will give you a long list of choices in a menu to use for manipulating the map. Some of the included choices are copy/paste, inverse, reverse, quantize, and step amount (up to 128 steps).

The Stacked Voice Tuning gives you control over each individual voice’s tuning. This works when you have set ACE to use the stack setting, which is the number of voices that are used in unison.

The Circuit Bending section allows you to imitate some of the issues that were sometimes present in the older, classic synths. Used the right way, this can add a good bit of analog realism to the sound you are designing.



The first thing I want to say in this wrap-up is that ACE really sounds superb. It has a very high quality of sound, and I feel that is definitely worth the extra CPU hit. The CPU usage can be high, but u-he does warn you of that up front. It occurs more often when you’re stacking up many voices, have it switched to the “Accurate” setting, and have a goodly amount of modulation going on.

Here are a few things I didn’t get to mention during the review, so here’s my chance: ACE has an easy to use MIDI learn built-in (right-click on a control), multichannel MIDI support, supports micro-tuning, three effects are included (chorus/phaser, delay, and tone), and the included oscilloscope is very handy. The display sizes in the latest version of ACE have been improved even further, as they now range from a 716 by 403 resolution all way up (in 10% increments) to 2048 by 1152.

The u-he folks claim that ACE is suitable for beginners, but it is a little complicated when you really get down to it. I mean, this isn’t Modular Synthesis 101 after all. On the other hand, u-he has produced many easy to follow tutorial videos, and they demonstrate how many types of synthesis can be accomplished. The manual is very good, but I feel the videos provided can really help.

To say I merely “like” ACE is an understatement, as it is now one of my favorite synthesizer plugins. If you’re even thinking of getting into modular synthesis, you simply have to try out this monster. ACE is available for $85 USD, which really is a bargain for how much flexibility and power it offers. You can find the demo version, plus more info about the synth plugin here:



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