Review: Softube Modular

Own a modular synth without the expense
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Own a modular synth without the expense
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It’s no secret that Eurorack synthesizers are very hot right now. Dozens of companies are springing up to make modules conforming to the Eurorack standard. Eurorack modules are generally smaller than modular synth components designed for other formats such as “5U” (Moog Unit and MOTM). They also tend to be (slightly) less expensive and more cutting edge.

Fig. 1. Just about every other kind of analog synth has been modeled in software, but virtual modular synths are a rare species. Despite perfectly straight patch cords, Softube’s Modular comes surprisingly close to the real thing. Softube Modular—from a company known for making accurate emulations of rackmount studio processors and guitar amps—looks, functions, and sounds almost exactly like a massive Eurorack system. Softube began developing Modular in-house, collaborating with Eurorack originator Doepfer to reproduce that company’s existing modules in software.

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Modular comes standard with 30 virtual modules, and you can simultaneously use as many of each as you need. Six are replicas of real modules from Doepfer, and three optional modules are replicas of real modules from Intellijel. Because Modular is expandable and Softube plans to release more modules (some of them free), you’ll be able to add new capabilities as they become available. For this review, I used all the included modules and all the Modular add-ons currently available: three Intellijel modules and Softube’s virtual modular drum machine, Heartbeat.

Because Modular encompasses so many modules and functions, the user manual has a lot of ground to cover. Clicking on Modular’s Open Manual button opens a PDF that covers dozens of Softube products. The sections pertaining to Modular could be more detailed, though, and you should download PDF manuals for the original modules whenever possible.


Modular’s greatest advantage over hardware is that you can save, recall, and edit entire configurations of modules, connections, and settings. It comes with almost 200 factory patches encompassing many different combinations. Although the process of rearranging modules is unnecessarily awkward, Softube says it is working on improvements.

Opening Modular displays an onscreen Eurorack case containing four empty bays, one atop the other. Between the top two bays are two main outputs with a volume knob and level meters; three buttons for adding, deleting, moving, and editing modules; four pairs of assignable aux outputs; and four buttons for sending control voltages from the aux outputs to real Eurorack hardware via any audio interface that can handle DC output.


To create a patch, select whatever modules you want to use and connect them via virtual patch cords. With modular hardware, you never have enough patch cords, but software patch cords are unlimited. Connecting modules couldn’t be more intuitive. Simply click on an output and drag-and-drop on an input. A thick colored line will appear, disappear when you move the cursor away from it, and reappear whenever the cursor is over any jack. You can connect an output to any number of inputs, but an input will accept a connection to only one output. To break a connection, click on the destination and drag away from it. Just remember there’s no undo function.

In addition to the Modular instrument plug-in, you also get Modular FX, an audio processor plugin that appears identical except for two input jacks. It lets you use modules to process external audio, recorded tracks, or other instrument plug-ins. Although the manual doesn’t explain how to use Modular FX, it didn’t take long to figure out. I wished I could resize the rack, though, because I seldom used more than two or three modules for audio processing. Some of the 34 factory patches for Modular FX used more than a dozen modules, though.


Fig. 2. Modular comes standard with 6 Doepfer modules, 4 DAW and MIDI interfacing modules, an effects module, 3 mixers, 4 sequencers, 12 utility modules, and 20 performance modules. Intellijel and Heartbeat modules are optional. The Doepfer A-110 oscillator, A-108 filter, A-132-3 dual VCA, A-140 ADSR envelope generator, A-147 LFO, and A-118 noise generator are the heart of the system. These are virtual-analog models of Eurorack hardware modules you can find on Doepfer’s website. You could easily construct a complete modular synth using only these six modules. All are typical subtractive building blocks faithful to their hardware counterparts with very few surprises. For example, the A-108 VCF models a self-oscillating lowpass transistor ladder filter with separate outputs for four cutoff slopes and a bandpass output.

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Most modules don’t emulate specific hardware, though. They encompass DAW and MIDI interfacing, sequencing, and various utility functions. The only effects module is a simple, single-tap delay line with a maximum one-second delay time. You also get three mixers: a four-input mixer for audio signals, a linear mixer for control voltages, and a polarizing mixer for adding and subtracting signals—for example, combining VCF outputs to achieve custom filter characteristics.

Sequencer 8, Sequencer 16, and the unusual 5-step Penta Sequencer have CV and gate outputs and knobs to set step values. Beat Sequencer offers a grid of buttons for programming as you would a Roland-style drum machine, with four channels, 16 steps, a swing parameter, and four trigger outputs for driving percussive sounds. For sequences longer than 16 steps, you can link sequencers.


Twenty modules are called performance modules, which furnish customizable knobs, sliders, and switches for easily tweaking parameters in real time. You can insert as many as you need in the same section of the rack for easier access than controls spread out over Modular’s GUI. I wish it were possible to assign controls to MIDI CCs so that I could control them with MIDI hardware, but at least Modular responds to DAW automation. I also wish I could create custom macros by assigning a single performance control to affect multiple parameters.


Intellijel’s Korgasmatron II ($49) is a dual filter that takes its inspiration from Korg’s MS-20 filter. Parameters for channels A and B are identical, and each has six modes: 6 and 12dB/octave lowpass, 6 and 12dB/octave highpass, 6dB/octave bandpass, and 6dB/octave band-reject (notch). Korgasmatron has a nice gritty sound and variable distortion when needed, and it can function as a dual sine-wave generator when self-oscillating. You can also crossfade between the A and B channels using the Xfade parameter.

Rubicon II ($49) is a through-zero, triangle-core oscillator designed for FM synthesis. It generates three types of pulse wave and three variations on a sine wave. Its through-zero FM, symmetry offset, and waveform-flipping parameters give it uncommon frequency-shifting and waveshaping capabilities. μFold II ($29) is also a waveshaping module with through-zero symmetry, but it needs a signal from another module to fold in two, four, or eight stages. μFold allowed me to make some very interesting sounds, especially when processing external audio.

Heartbeat ($169) is a separate product from Softube. Conceptually, it’s a comprehensive virtual analog drum machine plug-in. In addition to its own mixer, effects, and pattern generator, Heartbeat has independent sections for each of seven instrument types—two for kick, two for snare, and one each for hi-hat, percussion, and cymbal—each with ample controls for tailoring sound parameters. If you own Heartbeat, Modular can use these sections as sound source modules that have the CV, trigger, and audio jacks you need to connect them. Play them using either the Drum MIDI to Trigger module for real-time performance or the Beat Sequencer module for constructing drum patterns. Like drum modules in the Eurorack world, Heartbeat modules greatly extend Modular’s percussive capabilities.


Although I didn’t have a Eurorack system stuffed with identical modules to compare, Modular has an aural quality I associate with modular synths. It certainly sounds as convincingly analog as most softsynths I use. I wouldn’t hesitate to use it almost anywhere in place of a real Eurorack synth. Modular is a terrific educational tool for learning the ins and outs of modular synthesis, too. If you are considering a plunge into modular synthesis, you’d be smart to spend some time with Modular before you spend big bucks on a Eurorack system.

If Modular users were to buy corresponding hardware modules from Doepfer and Intellijel, they could design patches on their computers and then re-create the same patches in hardware. Conversely, they could also duplicate what they created using hardware in Modular and then save the patch, giving them an accurately detailed record of the modules, connections, and settings they used.


Owning and using Modular has obvious advantages. The whole shebang costs less than most individual Eurorack modules. A comparably appointed Eurorack system would cost well over ten times as much. Though you could buy all three Intellijel modules in software for $127, you’d pay $949 for their hardware counterparts. Unlike hardware, Modular will never need repair or warm-up time. However, because it is a rather recent release, it could use a bit more fine-tuning, and most of the factory patches are uninspiring. And depending on how many modules you’d use simultaneously, CPU load could be an issue.

The biggest problem with traditional modular synthesis is that it’s ephemeral by nature. Hardware patches are all but impossible to precisely duplicate. Once you put so much effort into creating a complex patch, you’re stuck with it until you’re willing to lose it. With Modular, you need never lose hours of work again. You can even share patches with other users.

Hardware is not without advantages, though. Eurorack owners have a much broader selection of modules available. You can resell your Eurorack modules anytime you want, and they won’t become obsolete if a manufacturer goes out of business and it’s time to update your computer.

Nonetheless, Softube Modular makes me feel like I acquired a mammoth modular system and I’ve been exploring its vast capabilities. Using it is so much fun that it’s easy to lose track of time. It can be challenging, like any modular synth, but the reward is learning to make sounds you couldn’t otherwise make without spending much, much more on the real thing. If you want to give Modular a try, demos are unrestricted for 20 days. I’d say that’s time enough to fall in love.


Realistic hardware emulation. Includes a boatload of useful modules. Exceptionally versatile, affordable, and expandable. Outstanding options available. High fun factor.


Can’t resize rack. Cumbersome process for rearranging modules. Only one effects processor. No support for MIDI CCs. No undo. Can be CPU intensive.