Make Mine Modular

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Photo: Geary Yelton

Relegated to the technological tar pits when inexpensive digital synths hit the scene in the '80s, analog synths are now being used by savvy sound artists for more than just creating phat bass lines and screaming leads. Modular synthesizers add color and attitude to your DAW tracks that can be difficult to get with plug-ins, while offering a wider array of effects and parameter control than stompboxes.

For example, one of Brian Eno's sonic secret weapons has always been the unique filtering capabilities of his EMS Synthi. Many of today's top artists — Nine Inch Nails, Radiohead and Tortoise, to name just three — are using analog modules to process audio in unusual and complex ways. Unlike a preconfigured mono synth, a modular instrument allows you to assemble a highly personalized system that fits your needs.

Although a hardware system requires a greater investment than its software counterpart, you certainly don't have to take out a second mortgage on the house to build one. A number of companies produce modules, and in most cases they are very affordable.

In this article, I'll explain what it takes to set up a system for the personal studio. But I'll start with the basic approach of running your DAW tracks through a stompbox so you can see the limitations.

Brute-Force Effects

Processing recorded tracks with guitar effects is fairly common in the studio. However, the level of real-time control you have over most pedals is limited to a couple of parameters. Other drawbacks to using guitar stompboxes to process your tracks include poor signal-to-noise performance and a limited number of available effects types.

Some pedals, such as the Moogerfooger line from Moog Music, include CV inputs that let you use one or more expression pedals to control parameters. But, again, you are limited to only a few simultaneous real-time controls — two feet and two hands. (The Moogerfooger MP-201 and CP-251 nudge Moog Music's pedal line closer to a modular synth system by providing additional control options, such as LFOs and sample and hold, among other features.)

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FIG. 1: In my studio, Eurorack modules from various manufacturers play well together (see Web Clip 1).

Although manufacturers such as DigiTech and Line 6 make digital guitar processors that let you stack and reorganize effects without the hassle of a huge pedalboard, the algorithms used in those processors are still fairly limited and are based on models of traditional pedal configurations. In addition, you usually get only a foot pedal or two for immediate parameter control.

The easiest way to process a DAW track through a stompbox is to simply plug into the effect's input and see what comes out the other end. However, patching a prerecorded track from your digital interface at line-level into a guitar pedal doesn't guarantee a clean signal at the pedal's output. Many guitar pedals expect to receive high-impedance, instrument-level signals from a passive electric guitar or bass pickup, and a line-level signal can prove overwhelming to many stompboxes.

EM contributor Eli Crews, who runs New, Improved Recording, handles the job with the John Cuniberti-designed Reamp. It accepts a balanced XLR and ¼-inch, +4dB input, and supplies an unbalanced output that is closer to what a stompbox wants to see. Simply plug the Reamp's output into the stompbox, and then connect the stompbox's output to a direct box to get a balanced signal that matches the level your DAW's interface expects. Of course, you can also feed the stompbox's output into a guitar or bass amp and, with a mic plugged into your DAW interface, add some amp and room tone to your processed signal. (Visit for more interesting ways to process signals.)

Crews notes that some modern effects pedals are designed to accept line-level signals. But if your vintage phaser is distorting (in an unpleasant way) when you run your prerecorded string tracks through it, the above setup will help you get cleaner results.

But what if you also want to synchronize your effects processing to the beat while occasionally adding another effect using a random pattern? That's where synth modules come in handy. Let's look at what is involved in selecting a starter system for processing audio.

Size Matters

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FIG. 2: The handy Blacet I/O 2225 accepts an input signal (on 1/8- and 1/4-inch jacks) and provides a switchable amplifier. The outputs include a pair of envelope follower (CV) outputs, a gate output and a trigger output.

Photo: Courtesy Blacet Research

To the uninitiated, the options available in analog synth modules can seem vast and confusing. Although there are different form factors, you greatly narrow down your module choices once you decide on the general size of the rack enclosure. The most popular form factors are the 3U Eurorack and Frac Rack formats, and the 5U Moog-style format. Each format is supported by several manufacturers, and some companies support more than one. Other modular synth companies — such as Buchla and Associates, Serge and Modcan — have proprietary formats.

Module size not only determines how much you can fit into a rack, but it also has an ergonomic impact. For example, the 5U Moog-style modules use ¼-inch cables and have larger knobs than the 3U formats, which support 3.5mm cables. Consequently, if you have big fingers and need lots of room around your hand when dialing in a patch, the larger formats are worth exploring. If portability is a major concern, investigate the smaller formats.

Another way to decide on a format is to begin making a list of the kinds of processing you want and start comparing prices and features between manufacturers. At some point, you'll triangulate on a set of modules, and the resulting format will probably suggest itself. If not, don't worry; it's common for people to use more than one format in their studios, and, ultimately, the modules in one format will work well with modules in the others (see Fig. 1). In some cases, it might take a bit of effort to get control signals of one system to a level where they will work precisely in another system, but that's more the exception than the rule.

Square One

Before you invest in any format, consider the kinds of things you want to do with an analog hardware processor. For starters, anything you can do with a stompbox can be replicated with a modular synth, so you can begin with those types of effects: filtering, distortion, phase shifting and ring modulation. What a modular system will add is the ability to control various parameters of the sound by hand (using knobs, a joystick or a ribbon) or by using control voltages (CVs) for automation. Often, a synth module will have a knob and a CV input to control a parameter. (If you're familiar with plug-in automation, then you already have an idea of how you could control hardware synths using voltages, gates and triggers.)

Analog modules offer many ways to create and use CVs. One easy way is to use a low-frequency oscillator (LFO) as a voltage source. As the LFO's signal rises and falls, it can raise and lower an oscillator's pitch or a filter's cut-off frequency. Then you can take the oscillator's output, for example, and use it as a CV to control another parameter of another module (or one of its own parameters), and so on. Right away, you can see that a modular synth allows you to explore complex methods of processing, such as CV feedback paths. If you don't fully understand what you're doing with a patch, that's okay: With a modular synth, you learn by patching.

For people who are new to modular synths, I recommend starting with a system that does one thing well. You can expand your palette once you figure out the next level of processing that you need. Beware of the empty-cabinet syndrome. That's the feeling caused by having a rack that's not quite filled with modules, and the sudden urge to splurge to fill the gaps. Save your money until you know exactly what you need.

As an example of a self-contained starter setup, let's assemble a system for creating complex filtering effects, one that would eventually provide a range from automatic wah-wah sounds to step-sequenced timbre changes. I would begin by looking for filter modules, of which there are many available. One common design is based on the vintage, Moog-style, 24dB lowpass filter. Quite a few companies make them, but each model sounds slightly different. If you simply want to approximate that old-school vibe, you'll probably be happy with just about any filter module you choose.

I would also get a second filter, one that has highpass and bandpass capabilities. The more CV inputs your modules have, the better, because you want as many control options as possible.

At this point, all you need is a power supply for the two modules and a cabinet to mount them in (either purchasing the proper rack or building one out of wood). Now you're ready to add serious attitude to your tracks — albeit, by hand. Just take an audio output from your DAW interface and plug it into the audio input jack of one of the filters. Then send the filter's audio output back to your DAW interface, tweaking the module's knobs to suit your tastes.

But what about all those CV inputs? Let's add a simple set of control sources to spice things up a bit.

I would add a module that offers one or more LFOs, and perhaps an envelope generator (EG) so I could shape my CVs a bit more. I would also consider getting an I/O module that would allow me to get the most from my DAW tracks. For example, Blacet ( and Doepfer ( offer input modules that not only let you amplify or attenuate an input signal, but they also give you a gate and trigger output based on the input. That output will be useful for module control and synchronization purposes (see Fig. 2).

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FIG. 3: MOTU Volta is a virtual instrument plug-in that provides a high-resolution way to control your analog synths using your DAW''s automation capabilities.

The result would be a five-module system that could take a monophonic, line-level input signal and filter it in sophisticated ways. Pricewise, expect to pay $75 to $250 per module, depending on the brand and the complexity of the circuitry, and a C-note or more for the power supply and rack. It seems expensive at first, but remember that this investment will outlive any computer or plug-in you are using today — you will have an effects processor for life if you care for it properly.

Crush! Kill! Destroy!

Filtering is but only one thing you can do with a modular system. One of the most popular ways to process sound is with distortion and waveshaping. So why not just run everything through an Electro-Harmonix Big Muff pedal and call it a day?

Again, a modular system lets you shape the distortion effects in subtle ways that a stompbox doesn't. Imagine being able to increase and decrease the amount of distortion to the beat of your song? Or perhaps change the quality of the distortion randomly or on every other beat? These types of processing are well suited to a small modular setup. In addition, bit reducers and other digital effects have been put behind modular synth panels, allowing you to use these kinds of processors conveniently within a patchable system.

May the Pulse Be With You

A common processing trick is to take a track from your mix that is providing a steady pulse (such as a click track, a bass drum or a hi-hat) and use it as your synth's clock source. One way to do this is to feed the track into a sequencer's trigger input. Other modules can divide the pulse into smaller musical units so you can subvert your four-on-the-floor beat.

When Alessandro Cortini was touring as the keyboardist for Nine Inch Nails, he would use the click track for each song (which was played from a Pro Tools session and used for synchronizing both music and lights) to trigger his portable synth rig. Consequently, no matter how he patched his synth, the results were locked in perfect time with the music, allowing him the freedom to concentrate on timbral nuance within the craziness of a live show.

Of course, you can also synchronize your processing via MIDI using a MIDI-to-CV converter. The output is usually a couple of CV signals and a gate signal. These devices are inexpensive and quite robust, and I highly recommend the investment once you get your feet wet with a system.

Re: Volta

The most exciting innovation for analog synth users in recent years has been MOTU's Volta (Mac, Audio Units), a virtual instrument plug-in that lets you harness your digital audio sequencer's high-resolution automation data for CV control using the DC-coupled outputs on a digital audio interface (see Fig. 3). By setting up the proper feedback path, Volta can also keep your analog oscillators calibrated.

“Ramp automation and anything created using drawing tools can be used as a CV,” notes MOTU's Matthew Davidson, who developed Volta. “This means you can easily create complex, timeline-based modulation. You can also sync [as many as] 24 LFOs with a variety of shapes, alter the symmetry of the shapes or sum multiple synched LFOs to create interesting periodic elements.” Combine the automatable power of Volta with a joystick or ribbon controller that you can work with in real time, and you get an unprecedented level of control over analog outboard processing.

To Infinity and Beyond

To learn more about the world of modular synths, check out the various forums for each manufacturer; you'll find Yahoo groups ( for many of them. In addition, the archives to online discussion groups such as Analogue Heaven ( and Muffwiggler ( are rich resources on modules and their uses.

But be forewarned: Processing audio through a modular synth is highly addictive. Once you hear how good it sounds, there is no going back.

Gino Robair is the former editor of EM.