“The breadth of control, countered with the joy of random probabilities, is simply fun”: ADDAC System 511 VC Stochastic Voltage Generator review

What is it?

The Stochastic Voltage Generator (511) is all about controlled chaos. It’s the perfect module for managing mayhem, done by setting limits and allowing the module to randomise outputs based on rules you define and as such can be used for modulation, melody and pretty much anything voltage controlled, which in Eurorack is almost everything. That means it can be the beating heart of a patch, or a very useful wingman.

The module itself is fairly small, considering what it is capable of. At just 20hp you can’t expect a knob per function control set, so the 511 uses a menu via some controls and a small screen. Don’t be put off by that, though. While menus can seem daunting and unintuitive, ADDAC has done a fine job here. The screen is small but very bright and crisp and the menus themselves are a doddle to navigate.

The panel is typically well-made and clearly labelled. Placement of the 511 is probably best suited to the bottom row of your case, as the patch points are all placed at the top, which makes sense, as you’re likely to interact more with this than you would with some other modules. Do check the depth of your case, though, as the 4.5cm depth of the 511 is a little more than some.

Controls for the module are split between a number of buttons, each with a secondary control via a long press, and a pair of rotary encoders for navigating the menus.

Patch points are split, so you’ll find all the CV inputs (of which there are eight) to the top right, with the Logic, CV and gate outputs to the right. Under these are four clock/gate inputs. There’s also an average mix out, which combines the four channels into one.

Below the ports are the main places you’ll interact, with the screen and rotary controls on the right and voltage controls on the left. At the bottom of the module are the buttons for lock, presets and states. All very easy to locate on the fly, being logically laid out. Although it took us a second to get used to ins on the right and outs on the left but that could just be us.

Performance

Let's start by looking at the menus, as that’s where a lot of time will be spent. The left knob is used to select a value, while the right-hand knob is used to change and set that value. It’s a very efficient system that is fast to adapt to and use.

The screen is a joy too. Broken down into easy to read sections, you can see a lot at a glance, from the active channel you are working with to any scale you are quantised to, probability settings and even polarity of each channel, distribution curves and mutes. That may sound like a lot to take in on such a small screen but working with it for more than half an hour it becomes second nature to give it a quick glance to understand exactly what is going on.

The buttons to the left of the screen have dual use, as mentioned. They are used for selecting channels, muting channels and holding the current voltage. This makes the 511 quite ‘playable’ and really useful in a live environment.

But what does the 511 actually do?

Well, the core idea is to generate random voltages while retaining control. This could be in the form of quantised varying voltages to output a random melody that can evolve over time, within a set of defined parameters. For instance, if you are quantised to a major scale, you could choose to have the probability of each note in the scale set the same, or set one or more notes to appear more frequently. This gives you the ability to discover some happy accidents based on your rules, or to imply a certain ‘feel’ based on your note choices.

This can all be clocked, so the notes fall on the grid, as it were. Great for outputting synced bass and melodies, that will mutate over time but remain in time. That said, the four channels can be given different timings, so they don’t have to stick to the same beat. This can be good for using one channel for a melody, while a second is used for modulation, where you might prefer there to be some drift from the main clock source. We like this for spacey, ambient patches, where lots of movement keeps things fresh.

If you do prefer a more synced approach, then the 511 has a handy copy and paste system, so you can align values between channels very easily. Then you can still adapt certain values if you wish, like changing probability or duration.

Another neat trick is the states system, whereby each channel can be assigned three states, or three different saved settings, each of which can be switched to via incoming CV. This makes it simple to make sweeping changes (or subtle ones) automatically, based on another modules output.

You might be wondering what the duration setting is and that got us at first too. Basically you can set a clock-based time for voltages to change, smoothly between the random values. Less important for short stabby melodies but very useful for slower, evolving voltage changes, where your output might be intended for modulation. This can be left stepped if that suits your project better.

What we think is a really special part of the 511 is the qualntiser. This can still be random but think of the possibilities. You could have one to four different random melodies, all in key with each other, with either synced or random gates. We like to think of this as playing chords with different amounts of spread and it works really well, producing some wonderfully musical results. There a bunch of pre-defined scales, as well as the ability to set custom scales.

The quantiser is a pretty deep part of the module, so dive in and explore, as you can do all kinds like defining how it adheres to a scale based on rounding up or down from an incoming voltage, or the limit in cents or octaves the scale will stay within.

And then there is the presets system, which is beyond useful. We used the 511 on our latest album and being able to save everything the module is doing for various tracks was a lifesaver. You can save all parameters of every channel, into one of 16 presets and recall them at any time. Some people may like to finish a track before moving on to the next but we like to flit between ideas as and when, and the presets allowed us to instantly recall everything we’d spent time on setting up and it saved us hours. This is something we’re used to when working on a DAW but is uncommon in Eurorack and we’d love to see more of this in other modules. It doesn’t break the freedom and experimentation of modular but does give some peace of mind for longer term projects. Plus they can be saved to your computer if you need to free up some room.

Verdict

The 511 Stochastic Voltage Generator is a stunning module. It offers ease of use, with levels of complexity that belie the user experience. The typically solid ADDAC build houses immense levels of ability and, while not for everybody, the menus are excellent, the breadth of control, countered with the joy of random probabilities is simply fun. It’s a musical and very rewarding experience.

Alternatives

Vermona MeloDICER: £439 at vermona.com

MeloDICER has some similarities but uses sliders for setting the chances of a note playing. It’s great fun to experiment with and is very playable.

Read more about Vermona MeloDICER

Erica Synths Black Sequencer: €510 at ericasynths.lv

A bit leftfield maybe but this sequencer has some tools for controlled randomisation which work really well. It’s big but fantastic.

Read more about Erica Synths Black Sequencer

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