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This Month’s Module:
 SynthTech E520 Hyperion Processor



The E520 is a very different take on Eurorack modular effects processors.

Unlike the Synthesis Technology E520, most Eurorack effects modules are based on either of two integrated circuits. The PT2399 delay chip was originally designed for karaoke machines. It’s popular in guitar effects pedals as well as lo-fi Eurorack delays. The Spin FV-1 DSP chip has a code library of reverbs, delays, and other common effects that manufacturers can use and expand on, in addition to writing their own effects.

By contrast, the E520 features a variety of new effects or extensions of old favorites. Most were defined by musician Robert Rich. Eric Brombaugh coded them from scratch using a 480MHz ARM Cortex M7 CPU. It has a lot more computing power than either of the more popular chips. Sixty-four megabytes of memory allow a maximum six minutes of delays and such. Compare that with the usual few seconds or even tenths of seconds you find in other effects. And the signal path is stereo 24-bit at 48 kHz throughout, which is higher than most Eurorack effects modules.


Version 1.0 of the E520 ships with 24 effects algorithms, with its spectral effects standing out in particular. These split the incoming sound into as many as 512 independent frequency “bins” so that it can process them separately. This allows delays, for example, to only affect certain frequencies, or to smear them across different frequencies. The bins can also be transposed in pitch. One of the most interesting of these algorithms is Spectral Drone, which was inspired by Michael Norris’ popular Spectral Dronemaker plug-in.

Among the delay algorithms is a re-creation of the old Lexicon Prime Time rack unit. Another, the very cool Chowder Delay, chops the audio into musical divisions and then randomly reorders, reverses, stutters, ratchets, and transposes them. A deep Pattern Delay features a large number of taps spaced at musical intervals to create rhythmic patterns from individual events. And if you like tape-inspired effects, you’ll find a Reversible Delay as well as a Looper that can save its contents to an optional microSD card. More delay algorithms are available, too.

Re-creations of other traditional effects include a phase shifter with the number of stages adjustable up to 24. There’s a flanger with diffusion delay, a four-channel chorus, and a Shimmer Reverb—a diffusion delay with clean pitch-shifting it the feedback loop. You also get frequency shifters, the vowel formant-based Voder Filter, and a Dual Mono mode that provides a subset of algorithms available independent on the left and right channels.

User Interface

Given that the E520 features the kind of deep, advanced effects you’d normally find in software-based plug-ins, it also takes a different approach to its user interface.

Rather than long lists of parameters, the E520 presents just a handful of musically-useful parameters per algorithm. Each one features four adjustable values, three switches or toggles, and feedback plus wet/dry mix. A fourth button acts as an effects bypass switch. All appear on the main menu screen for an effects algorithm, along with dedicated knobs and switches. The four adjustable values, feedback amounts, and wet/dry mix also have control voltage inputs, each with its own attenuator.

Each algorithm also has a Page 2, which contains source assignments for each of the adjustable values. They default to their dedicated CV controls (front-panel knob plus voltage-control input). However, you can alternately assign it to a fixed value or one of the four internal LFOs. Each algorithm has a highpass filter on its input and a lowpass filter on its output to help sculpt its sound. A few algorithms also have additional parameters on Page 2.

Each of the internal LFOs—which you access from Page 2 using the dedicated buttons underneath the LCD, or from a separate Top-level menu—offers a wide range of both periodic and random shapes. Each LFO has its own depth and a wide speed range: from under 0.1 to over 100 seconds per cycle. To drive other modules in your system, you can optionally assign one of the LFOs to an auxiliary output.

Deeper Still

Page 3 allows you to save as many as six different presets per algorithm. You can quickly recall four them using the dedicated buttons. A separate Top menu item saves an additional 24 patches, which include recalling the desired algorithm. Each patch stores all the necessary parameters, including LFO settings. You can save and recall the module’s entire state from the optional microSD card. That’s great for archiving sessions or guaranteeing setups for live performance. 

All of these controls (plus a dedicated tap tempo button and input jack), combined with a spacious grid-style layout, result in a module that is definitely not small. It takes up 48 hp of width, although it is shallow at only 35mm including the power connector. 

I created a video quick manual for E520 for SynthTech that demonstrates this interface in action and gives a quick preview of some of its algorithms.

The only time I repeatedly felt something was lacking when editing an algorithm was when it came to tap tempo, which is currently limited to quarter notes. This is supposed to be greatly expanded in the version 2 firmware due this fall. Until then, use a clock divider/multiplier module to fine-tune your synchronized timing divisions.

Audio Interface

Another unusual feature of the E520 is that, by design, it works either with modular or external equipment. A pair of preferences allow you to set its inputs and outputs to either modular or line level. Modular level is optimized for ±5 volts and clips at ±6.5 volts, which is below the normal ±10-volt range of many other Eurorack modules, so be prepared to attenuate your inputs. Line level is optimized for the -10dBV standard of ±0.45 volts and clips at ±2.5 volts.

The E520 has two main reasons for including the line-level options:

  • Effects often appear at the end of the modular signal chain. Setting the E520’s output to Line allows you to connect it directly to a mixer or computer audio input without the need for a dedicated level matching module or heavy attenuation downstream.
  • By setting the E520’s input to Line, you can patch in external keyboards directly without the need for additional level matching. Paul Schreiber of SynthTech points out that unfortunately, there is no standard for the output level of keyboard synthesizers. A keyboard’s specs doesn’t usually mention level—although it is generally in the line-level range. Fortunately, most keyboards have their own output volume controls if needed.

Personally, I patch my modular effects into the effects loops of my external mixer. This normally requires line-level shifting modules before and after the effects modules; the E520 will allow me to skip those. Since I use +4dBu levels with my external mixer, I will be using the E520’s Modular level setting to ensure plenty of headroom.

Where It Sits in the World

Given the Synthesis Technology E520’s goal of being different, you should not think of it as a replacement for your favorite reverb, granular/sample slicer, or multi-effects module or pedal. Instead, think of it as expanding your effects vocabulary. Not everyone will love every effect, but I believe most will find some new sounds to explore. The E520 makes that exploration easier than dealing with the typical plug-in or rackmounted effect.

Website: Synthesis Technology

Price: $649 (pre-orders start shipping in July; dealer orders in October)

Synth and Software would like to thank longtime modular user and former synth designer Chris Meyer for his contribution. Chris is the force behind Learning Modular, where he teaches you how to master modular synthesizers.

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