Schulze Modular Synth

Schulze Moog Modular

Overview Back in the mid 1970’s one of the first musicians I listened to who was making electronic music was Klaus Schulze, and I searched out his first 5 LP’s. Klaus bought a second hand Moog IIIP and double sequencer just before Xmas 1975, with a record advance (due to the success of Timewind). It became the focal point for his live shows, and it was used in many albums for the next 5 years. Klaus moved with his Big Moog into the German countryside after living in Berlin and I started studying electronics at University after building my first synthesizer.

The “Big Moog” was used from the April 1976 tour for many years, until it was retired during the digital 80’s. It re-appeared in the Dark Side of the Moog albums with Peter Namlook in the 1990’s, as Peter had bought it, but after 10 albums he sold it on eBay for £21,000. I could never afford such a large Moog synthesizer and I have never tried cloning the circuits, unlike ARP and Roland synths of the 1970’s. But I do love the sound it makes, so I can now build one!

Behringer System 55

Behringer System 55 With the release of the Behringer Moog module clones in 2020, it is now possible to recreate a Moog IIIP and build a Schulze setup at around £2,500 rather than £35,000! The System 55 was US$8,085 in 1976 without sequencers, equivalent to £40,000. The IIIP has the original 901 VCO’s, whilst the Behringer has the 921 VCO’s.

I wasn’t sure how well the Behringer clones were made, so I bought a few to try out and measure. You can read about these tests, and how I have setup my Schulze Modular in the attached web pages, and there are some useful videos in the sidebar. The initial modules passed the test and I went on to acquire a full System 55, and Complement B.

At the core of the Moog IIIP are an amazing 10 VCO’s, and one of each of the filters; Fixed, Low Pass and High Pass. It also has 3 VCA’s and envelope generators, and some utility modules. The Moog System 55 is an update on the IIIP with a few changes (no 904C) and modern stable VCO’s. It is an excellent basis for building my Schulze modular, but there are some gaps;

  • 905 Reverb – AION version can be used but I will use digital FX
  • 984 Quad Matrix Mixer – the AION version can be used
  • 904C Filter Coupler – the AION version can be used but I may build one
  • 993 Trigger Controller – I have built one

Behringer have also launched the sequencer modules (960,961,962) which means I can build a Schulze Double Sequencer. However all these modules do not fit into one dual row case even if 140HP wide, so I will have 2 Mantis 104HP cases and a separate case for the Complement B. I will re-balance the number of filters with the number of VCO’s in the overall design. I also have a voltage controlled clock divider and a note quantizer, for ratching, and Doepfer make both of these in vintage black which sort of matches the Behringer modules.

Learning Curve The Moog modular, and therefore any clone, has some different approaches to modern Euro Rack, and its important to get familiar with these differences;

  • Gate on is a S-trigger, a short to ground
  • The sequencer modules use familiar V-triggers
  • Control Voltages are +/-6V
  • Audio signals are typically +/-2V
  • A 921 VCO works well as a LFO
  • 921A driver is needed for multiple 921B VCO’s
  • There are separate attenuator modules to control VCF, VCA, VCO input levels
  • There are separate CV input selector modules for the VCF and VCO
  • The Moog has internal busses which the Behringer does not
  • With all this patching in Euro Rack size there isnt much panel space left!
  • Typical Moog systems only have one VC LPF and no S&H

Pre-Patching The original Moog IIIP had internal “trunk” lines that carried the CV and gate signals across the various modules, and utility modules in the lower control panels that enabled them to be selected into the VCO’s and filters. The Euro Rack standard has no notion of control signals in the 10 pin power connector, just a single CV and Gate in the 16-pin connector. Behringer modules expose the “trunk” lines via front panel sockets, so they can be easily used and do not use 16-pin connectors.

Behringer have included two utility modules; the CP3A-O to control VCO’s and the 992 to control filters, but these require external patching cables to function. With my objective of reducing patch cables I have implemented internal patching as far as possible, as on the original Moog.

Summary The Behringer Moog modules are well built and usually aligned and calibrated properly, with only an occasional intervention needed (like VCO Scale). The low cost of each module is attractive but its important to budget for Mixers, Attentuators and Utility modules to augment the core modules, as there are no input level controls. This adds cost, space and patch cables. It is easy to build a 3 VCO synth with LPF and VCA/ADRS’s but that can be done at a lower cost with a Model D.

I suggest building up a bigger modular system with more sound possibilities, with at leasts 2 banks of VCO’s, use all the filters and add at least one sequencer. It is a bigger investment but it opens up a lot more sound possibilities. My Schulze modular adds some custom module to the Behringer line up, and is currently under construction.

The small Euro Rack format with no internal busses and the need for small components means a 5U system is inevitably going to sound better and be easier to use, but at a much higher price point. The 923 filters illustrate the issue of using smaller (possible cheaper parts) where the potentiometer max travel is disappointing.

Mods and Extra Modules I have modified some of the Behringer modules (911 Envelope Generator) and added three new ones;

  • 993 Trigger Controller
  • 928 S&H
  • 1631 Ring Modulator

This is explained in the Mods & Modules page. Klaus add a set of PPG 300 modules in 1976 above the “Big Moog”, including; 2 analog sequencers, 3 VCO’s and various filters and a ring modulator. You can see these modules patched into the “Big Moog” in live concert pictures. He also started using two MiniMoogs (for solos) in addition to his ARP white Odyssey, an EMS AKS and a 2600. I use a Behringer Poly D and KARP Odyssey.

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