3U Modular Synthesizer Format

Because of the easier transportation, I decided to implement a EURORACK instrument that was friendly to travel. While my MOTM synthesizer was "classic", ie "eastcoast-ish" (Filter and ADSR with VCAs), I had designed the Eurorack Synth more "westcoast-ish", something FM-heavy, with Waveshaping and LPGs.

Here is my last Eurorack full instrument to be seen, which existed for only six months. A 600TE travel instrument that can be folded up easily (in patched condition) and is about as big as a tenor saxophone case. It was perfect for me, but I was not satisfied with the Eurorack format (12V). When I got the opportunity to take over some Buchla Clone modules from Roman F. (the man who had developed many of these Buchla Clones), I switched to the Buchla 200 Series.

Eurorack is ideally suited for learning modular synthesis and it is fun to try everything out. Through a lively used-market, you can get rid of modules at good prices - or can buy or exchange other modules at a lower price.

Basically it is likely that during the first years a lively module exchange takes place - in contrast to MOTM or Buchla, there are so enormously many modules (which are also available!). This also has a much stronger effect on the readiness for replacement. One has to pay close attention to the modules before exchanging them. A certain GAS resistance is certainly helpful (GAS = Gear Aquisition Syndrome), otherwise it can be expensive.

What I found very difficult was to give the instrument an instrumental unity - an instrumental character. The right weaknesses. A life of its own.

(My) Case Example

Tour De Force through Euroland

    In just two and a half years - my Eurorack time - I have built four cases (and am now Case specialist!). The first, with 4x84TE and 19 inch - was with a Doepfer-PSU2 transformer undersupplied, because I had increasingly Mini-Modules (4TE), whose consumption accumulated itself. Also, I wanted more modules. The second case was 4x119TE and had 2x PSU2. The energy crisis was fixed, but weight and 230V inside the case did not please me - I already built the third. The pictures show the growth and change of my system.

    With the 19-inch = 48.26cm size I had a baggage-enabled case, but I find it as an instrument just too narrow. Also the module selection is very limited and it is always missing space. In response, I had many small modules attached, but for the last, the mA of the transformer no longer sufficed.

    The second case was only slightly larger with 65cm, but it was much more comfortable. What annoyed me permanently, however, were the, now two ring core transformers (PSU2). They are heavy and dangerous. On this type of instrument, a module space is often empty and then you can go unimpeded to the transformers, which are also dangerous when they have been disconnected from the mains before.

    Also the firwood of the first two cases was very heavy and just at this time, the Audio-to-CV modules from Expert Sleepers opened the door: 2 channels audio from the computer could be generated to 40 CV signals. So it was time to build an even bigger case, in which finally the last weaknesses of the predecessors were repaired.

    The third case I had adjusted to the width of the keyboard and above the upper module was now no more wood that concealed it and narrowed the access. As a wood, I now chose poplar - as is the case with most of the old instrument cases. This case was complete manual work - the first two cases were CNC-milled.

    Since, with the TipTop Zeus Studiobus, a new, external (switching) power supply with 4.6A was on the market, I have separated from the ring core transformers. A noticeable relief!

    In the instrument were 80 CV-outputs from the computer and even the large Verbos modules did not look huge any more. On board were 9 oscillators, 1x noise, 6x filter, 2x wavefolder, 2x RM, 7x EG, 5x LPG, 14x VCA, 3x mixer, 3x controller (ribbon and pedals) and some utility modules such as switches, Logic, Crossfaders and Multiples. Besides, Rectifier, CV-Tools, S&H, Clock-Divider/Sequencer, Switching Sequencer and a Quantizer.

    There was finally "everything" here - and yet no joy wanted to arise (except on the cases). Certain things just do not fit me in Eurorack format. Many modules overdrive too much, if not a VCA for lowering sits behind - so you need more "Attenuverters". Many modules were either too "changeable" (eg Plan B, ingenious modules, but they have to be adjusted constantly and have many weaknesses / need service) or "bad" modules, which tend to use a side effect of a "reworked" IC and their characteristics with too many "secondary noises" (clipping) (eg Doepfer RM). Above all, it is too fiddly - I almost felt like a dentist who has to work all day on 10cm2. I do not like the Pots, except for a few exceptions. Fiddly. The + 12dB output annoyed me, since I make audio connections with the computer also in the middle of the patch. However, this always requires a conversion balanced/unbalanced and a volume and impedance adjustment. All this is, of course, only for me, part of my search. I am 2 meters tall, pianist, almost 60 and already have my ideas. Without a doubt the Eurorack represents the largest variety of all formats.

    Two brands are surprisingly close to an overall instrument sound. These are Doepfer and Analog Systems. They offer an incredibly wide range of modules. Perhaps the trick with the Eurorack is not always getting the "favorite modules" ... But that's hard. There are great manufacturers: ADDAC, Aion, Erica, Intellijel, MakeNoise, Synovatron, Toppobrillo, Verbos ... and so many more.


    The blissful Remnant


    This is my last Eurorack and it is the extension of my Buchla - with its own power supply (Rowpower-30). It is a "control and vector mix unit" and most of the modules are from Expert Sleepers: ES-40 (Audio to CV) with 5 expanders and input module. On the ES-block I have a Synovatron module with five GT-elements to convert Euro-gates (5V) or triggers (10V) into Buchla-stepped-pulses (10,4V trigger with 5V gate). I have the Expert-Sleepers "Set" twice - first as a backup and secondly for my MOTM Modular, in case more than 40 x CV are indeed needed from the computer...

    As a vector mixer (with joystick) the "Planar" from Intellijel is really worth its weight in gold. The two mix outputs of my Planar modules run into the Antumbra DVCA (Micro Mutable Instruments uVeils). I control one of the two VCA's with the ADDAC301 Floor-Control Module and a Yamaha FC9 CV pedal - so it serves as a volume pedal for one Planar. (After I had discovered with some surprise that a Euro VCA just opens and closes - and what goes in comes out exactly the same way - whether it is +12dB or 3dB (Buchla volume)…) sometimes you are astonished about the simplest / most logical things!

    Since I keep the Planar modules in a mini-case in front of the Buchla and I don't want unnecessary cable tangle (there would be 10 cables running all over the instrument), I bought a Doepfer Multicore module set. So it can be patched with ultra short cables (even during transport) and is connected to the synth with two Eternet cables.

case assembly

DIY with wood

    Readybuilt cases are sometimes shockingly expensive - a self-build is therefore budget-friendly and creative. A beautiful wooden case gives the instrument an individual touch and some "warmth". It does not necessarily have to be done all by itself - certain gradations are possible, in order not to overload the own DIY energy.

    Who, like me, plans with oblique angles and is not a proven hobby carpenter, should let the wood be sawn by experts. To cut these angles and shapes appropriately - with inadequate tools or even in the construction market, it would lead to unsatisfactory results. For the wood and the cut in the carpentry, one does not necessarily pay more than in the construction market only for the, possibly unsuitable, wood. For that it is transportable and shock-resistant, I had first chosen firwood. Poplar is, however, significantly lighter and was the wood for my third case.

    Of course, it is more beautiful to omit the rack ears of the module carriers (frames), also to make the edges of the case unnecessarily wide. The ears must therefore be replaced by simple aluminum profiles, which can then be screwed from the inside in the case.

    The resulting metal work is a bit painful, but it is possible - the biggest difficulty is to drill the holes exactly (but rather the locksmith?). It is ideal to slightly mill the two inner holes from the one side and the two outer holes from the other side with a countersunk drill so that the screws can be countersunk. The photo shows the side section yield of a 2m aluminum profile. The sawing out of the hole for the power connection in the fencing was less serious than initially feared.

    When the wood is stuck - glue sticks better than screws - and the frames screwed, the most is done. As can be seen, the drill holes for the power supplies and busboards in the rear walls have already been implemented. I recommend Plexi templates for simplification.

    Now a few dabs of lacquer, handle, locks, hinges and rubber feet are missing.

    The rails (crossbars) are of course available at

Audio-to-CV / CV-To-Audio

Expert Sleepers
  • CV can also be generated directly from the audio interface. For me it is the modern connection of computer and synthesizer. A fantastic collection of extremely useful CV plugins comes with the Silent Way PlugIn Suite- DC, LFO, Step LFO, Quantizer, Trigger, CV Input, CV To OSC, CV To MIDI, AC Encoder and Voice Controller. It is therefore also possible to convert incoming CV values into midi or OSC data. Due to the OSC compatibility, controllers which are quite simply corresponding to each other, e.g. On iPhone or iPad! All parameters also have a Midi address. This is VERY extensive - only the voice controller has 122 parameters! In particular the traveling modulator will be pleased that the included functions. In the future some modules can be left at home.

    Of course, the functions of these plug-ins can also be programmed completely with Max / MSP, but the SilentWay plug-ins are so good that they can easily live in the vst-object and only control needs to be programmed. Then no window for the plug-in has to be opened.

    Although these plug-ins can be used directly with DC-coupled outputs of some audio interfaces, they can achieve significantly better results - and then also AC-coupled - with the aid of the Audio-to-CV modules from Expert Sleepers.

    For me, the Expert Sleepers modules are THE Missing Link par excellence! A modul system suddenly takes on a completely different meaning! The calibration and tuning can be automated - it is not necessary to use more digital modules! Sounds, if identical patched, are reproducible even with the most complicated value changes - so exactly - what is normally not possible with such a system...