Rob Hordijk Design

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Rob posing with one of his modular systems.

Rob Hordijk Original Design are the "Dutch West Coast"[1] style 5U (Moog Unit) modules designed and crafted by Rob Hordijk; based in The Hague, Netherlands. Except for the Benjolin, the designs are not available for DIY.

As Rob has never had a product website for his instruments, the source for much of the information about them comes from direct contact via email - cited directly as Rob Hordijk [2]


Born in 1958, self described "synthesizer designer and builder,[3]" Rob Hordijk began learning electronics from around age 12 after developing a fascination with the glowing tubes in stereo amplifiers.[1][4] When he was 14 his father who had noticed young Rob's interest gave him a subscription to an electronics course, which lead to an examination for a ham radio license.

Trained as a designer and not a musician, Rob came from an arts background, studying as a sculptor and jeweler in the 1970s. He approached electronic music in a similar spirit to abstract painting, inspired by the ambient works of Brian Eno, and Luigi Russolo's Intonarumori instruments; where attempts were made to blur the boundaries between music and art:[1]

"In those days I was quite interested in the idea of sound as a material to be sculpted, in the same way you can sculpt wood and metal. [...] You can make mechanical objects that make all sorts of sounds, or you can make electronic objects that make all sorts of sounds. but what I like about the electronic objects is that you don't see what makes the sound. [...] It opens the way to sort of make it a bit mysterious."[1]

In the early 1980s as various integrated circuits, micro-controllers, and processors became available to hobbyists, Rob began buying things such as the early Curtis chips and RCA 1802 based SuperElf processor board out of curiosity more than professional ambition.[1][5] Later switching to an Apple ][+ and the Mountain Hardware Music System, for which he developed a Forth language version that could do all sorts of stuff with the Mountain cards, like KarplusStrong-type plucked string sounds and pitch shifting.[5] His first introduction to a DSP was to the DMX1000 around 1984. In 1986 he switched to Atari ST and an Akai S900.[5] These days he is a Clavia Nord Modular G2 aficionado.[5]

"I am not really a gear freak. But I do believe in mastering synthesis techniques, in making synthesis a second nature, so to be able to fully concentrate on the creative processes."[5]

After finishing art school, Rob also completed 11 years of study in Information Technology, learning about design methods and inventory control.[1] As well as his own instruments Rob worked on the Nord Modular G2 including contributing many patches to the Nord Modular online community, and wrote a comprehensive unofficial manual of the instrument. He has produced music for environments, buildings, film, and dance performances, but is yet to produce an official release on a label.[5] As of 2022 Rob has announced his retirement and will no longer be taking orders.[6]

A Rob Hordijk Original Design modular synthesizer (left) with other instruments.
A Rob Hordijk Original Design modular synthesizer (left) with other instruments.

Design Philosophy

Rob's personal definition of a modular synthesizer is more to do with modulation than modularity; referring to functional modules as 'sections'. Everything is supposed to be able to modulate or effect everything else. All levels within the system are optomised for comparability with one another.[1]


Inspired greatly by the ergonomics of his first syntheseizer, an EMS Putney, as much as negatively inspired by an early Doepfer system he owned, Rob's designs always keep the performing musician in mind saying, "the comfort of playing is much, much better in my opinion, with larger systems."[1] In keeping with this ergonomic priority the input and output jacks in Rob's designs are all at the bottom of the modules keeping them well clear of the knobs.[1] In response to a question about whether this rigid format becomes limiting Rob responded:

"It is often a good idea if you design something to impose a certain limitation upon yourself. Basically the way I design is at first I go wild, and go complex, until I feel that I've hit some good stuff, and then I simplify. And this process of simplification is quite important because maybe I have a design that could have like 14 knobs and 18 connectors, and then by simplifying it back to 8 knobs and 10 connectors with the most important functions that actually tends to add strength to the design."[1]

This design philosophy extends behind the face-plates too, where consideration for ease-of-construction is just as important. With few exceptions, all Hordijk modules consist of 8 pots and 10 jacks. These can then be easily built in batches using two underlying PCBs, one for mounting all the interface components, and another for the underlying module functions, connected with flat ribbon cables and all constructed with the same hardware.[1]


Functionality-wise Rob also draws heavy inspiration from chaos theory which he studied in the 80s reminiscing, "in those days it was more about graphic functions and little pictures but I was curious about how to apply them to music." After some disappointing experiments he learned a couple of tricks that produce musical results.[1]

Making a strong distinction between chaotic and 'random' behavior, Rob emphasises the way a disturbed chaotic system tends to seek stability, or a number of balanced states called 'strange attractors'; These balanced states can produce patterns, and when the patterns are short enough to be recognised can produce very musical results. He believes using these methods is the best way to breathe a kind of life or personality into electronic instruments.[1]

Workshops and Lectures

Rob has given a handful of workshops and lectures both demonstrating the functionality of his instruments, and explaining the design philosophy behind them. These include:


While self confessing, "I'm not a performing artist, I'm a synthesizer builder."[3] Rob has performed a number of times demonstrating his instruments in a more creative context as opposed to purely technical demonstration. These include:

Modular Systems

All circuitry is original and follows Rob's own concepts based on over thirty years experience in sound synthesis and electronic design.[2] He has complete control over the whole module building process; Research &Development, prototyping, panel design, cutting, drilling, PCB etching and populating, final hardware assembly, calibration and testing. All components and every piece of hardware is carefully selected for reliability and comfort in use.[7] Panels with the signature Original Rob Hordijk Design are both designed and built by Rob Hordijk in his workshop in The Hague, The Netherlands.[2]

Rob's philosophy and concept of a modular system is that each 'function' has its own inputs and outputs and should be patched up with cables, and not specifically that each function should be a separate physical entity. So, a triple panel is more like a 'section', offering specific musical functionality by grouping together a sensible collection of functions.[2] Within a triple-module there are several internal normalizations on the input and output jacks, but there are very little 'module to module' normalizations in triple panels and no 'triple to triple' normalizations.[2] Systems were built in a number of different configurations and cases depending on the customers request. A full four triple-module system in a plywood flight case weights about 23 kilograms, the lightweight flightcase reduces this to 16 kilograms.[2]

As everything is hand built there can be minor cosmetic issues like dustmarks anodized into a frontpanel or some lettering slightly out of focus, basically the usual things that are simply unavoidable with handwork. All electronics however are thoroughly tested and burnt in for several days before a system leaves the workshop. Only high quality precision components are used for the electronics and all pots are of the 'conductive plastic' type that will never develop crackles in the sound and easily last ten times as long as the more common carbon pots. Everything is designed to last a musicians lifetime and first time owners have unlimited warranty on parts and repairs.[2]

Format and Power

Rob's modules conform to the 5U (Moog Unit) (222mm / 8.75") standard. Single modules were produced 2U wide, which Rob later refined into a triple-module 6U (325mm / 12.79") wide standard.[2] A frame holds the modules in a way that it becomes one solid block. A frame can easily be mounted in a DIY cabinet made of just four shelves, it is fixed in a cabinet with a set of woodscrews from within the frame into the side shelves. Frames can be made up to three triples in width (976 mm wide) and basically any number of rows in height (225 mm per row). The most popular frame is two rows of two triples and measures 651 mm in width and 451 mm in height.[2]

The plywood flightcases have their power entry either on the left side or on the right side of the case. This should be specified when ordering. The lightweight flightcase has its power entry on the front and for this it needs the TriLFO-Matrix6x4-Nodeproc-MIDI-IECinlet triple or the Rungler-Matrix6x4-Nodeproc-MIDI-IECinlet triple. It lacks the +/-15V MiniXLR power outlet that is available on the other MIDI triples. The MiniXLR might be used for future expansions, to power e.g. a Blippoobox or for powering DIY projects. It should be considered just a convenience if ever needed and not a necessity.[2]

While the panels conform to a 5U MU standard the power distribution board uses MOTM-style connectors and modules with the +/-15V MOTM header can be readily connected and used. However MOTM modules use another 44 mm based grid than the 107 mm MU grid used in the triples, so they would leave a small gap. However and more important: the standard MOTM mounting holes are not compatible with the metric frame profiles, so they can not easily be fixed in our frame. In practise this means that in a user built cabinet with a section for a frame and a section for MOTM modules the MOTM modules can be powered from the Meanwell PSU + power distro board, but it is physically not feasible to mount a MOTM module in a frame without drilling extra mounting holes in the MOTM module front panel.[2]

The power supply used is a Meanwell RD-3513 set to +/-15V. It accepts an input voltage between 100VAC to 240VAC, meaning it can be plugged into a wall anywhere in the world. One PSU can safely supply current to four triples, for a bigger system a second PSU is recommended.[2]

A Rob Hordijk Original Design Modular System
A Rob Hordijk Original Design modular system, showing four triple-panels in a complete case.


Modules came with various combinations of the following single functions, though some smaller functions were combined; for example the PHASER and FREQ SHIFTER have appeared in both dual and combination formats.

Other Instruments


This page uses Creative Commons Licensed content from Mod Wiggler Wiki:Rob Hordijk Designs (View authors).

  1. ^ a b c d e f g h i j k l m n o Episode 205: Rob Hordijk (2017) Art + Music + Technology Podcast
  2. ^ a b c d e f g h i j k l Rob Hordijk
  3. ^ a b Rob Hordijk Presentation & Synth Tutorial // Modular Meets Leeds 2017
  4. ^ The Designer by Franz Schuier, 2008
  5. ^ a b c d e f Hello to you all, forum, 29 March 2004
  6. ^ Mod Wiggler forum: Hello Hordijk
  7. ^ Mod Wiggler forum:The Hordijk project

External Links

Pre-built Eurorack Modules