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). This R.A.Moog IIIP was probably made in 1969 and initially sold to Florian Fricke (Popul Vuh) in West Germany, who recorded with it in 1970/71. After a guest appearance on Tangerine Dream’s album Zeit in May 1972, the Moog seems to have been stored for 2 years.

This was the typical story of the 1969 Moog Modulars, bought by rich musicians, production teams and ad agency’s because of the success of Switched on Bach (1968). The rock musicians (e.g. Beatles, Hendrix, Rolling Stones) found it hard to integrate the revolution sound into the music they made. After a few experimental and pop records (or no use at all – Jimi Hendrix) the expensive IIIP’s were cascaded down into the hands of musicians who did harness the unique sounds.

The Rolling Stones IIIP (September 1968) was eventually bought by Tangerine Dream, making its first appearance on the Phaedra album recorded in November 1973. Klaus Schulze immediately recorded with his IIIP in January 1976 (Moondawn) and used it on many albums for the next 5 years, as well as the focal point for live shows from April 1976 until the mid 1980’s. Keith Emerson bought his new Modular ICA model in 1970, which was an expanded model Ic with presets.

Big Moog – Feb 1996 Copyright Sound on Sound

KS Moog IIIP In the  Autumn of 1975 Klaus moved into the German countryside after living in Berlin. At the same time I started studying electronics at University of Essex after building my first synthesizer. Commercial synthesizers were expensive in the UK at that time and hard to find outside of London. The “Big Moog” arrived in the countryside of western Germany and was used until it was retired during the digital 80’s.

The 1969 oscillators sounded great but the tuning was a frustration that digital synthesizers overcame. It re-appeared in the Dark Side of the Moog albums with Peter Namlook in the 1990’s, as Peter had bought it from Klaus, but after 10 albums it was sold on eBay for £21,000. It is now in a private collection and does not seem to have been recorded with.

Klaus sold off his PPG modules sometime in the 1980’s including the PPG 303 voltage controlled modifiers which were in the “Big Moog”. The 303’s were replaced by the original 991 Fixed Filters, 994 Multiples and a blank panel in Cabinet 1. The frequency meter was retained in Cabinet 2. Klaus also changed the order of the cabinets to 1,3,2,4 whilst recording Dark Side of the Moog with Peter Namlook – see picture in 1996.

Behringer System 55

Behringer System 55 With the release of the Behringer Moog module clones in 2020, it became possible to recreate a Moog System 55 in Eurorack, and build a “Big Moog” like-setup at around £2,500 rather than £35,000! The System 55 was US$8,085 in 1976 without sequencers, equivalent to £40,000. However the earlier IIIP has some unique features , which Behringer have not attempted to replicate. Specifically:

  • The early 901A/B VCO’s
  • The 984 Quad Mixer
  • The 904C Filter Coupler
  • The 991 Fixed Filters (removed by KS)
  • 993 Trigger Controller
  • 905 Spring Reverb (removed by KS)
  • The internal busses and trunk lines.

Initially I worked with the Behringer modules, but over times I have designed and built AMSynths modules to enable a true Moog IIIP experience, in terms of workflow and sound. This includes replicating the PPG 303 VCF/VCA modules that Klaus added into his setup (replacing the reverb, fixed filters and multiples).

Moog Modular IIIP At the core of the system 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 and modern stable VCO’s. The 984 and 904C modules were dropped from the System 55 by Moog, but they retained the 993 and 905.

Behringer also launched the sequencer modules (960,961,962) which means I can build a Schulze Double Sequencer. I have used three Doepfer 9U 84HP cabinets to house the Moog modular. This provides more rack space than the four cabinets of the IIIP, which means I can add another set of 904A/902/911’s with a CP4 console panel. I have added a voltage controlled clock divider and a note quantizer, for ratching, into the sequencer cabinet.

Learning Curve The Moog modular, and therefore any replica, takes some different approaches to a modern Euro Rack system, 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 901/921 VCO works well as a LFO
  • 901A/931A driver is needed for multiple 901B/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
  • The Moog has trunk lines that are simple cables from the front panel to the rear
  • With all this patching in Euro Rack size there isn’t much panel space left!
  • Typical Moog systems only have one VC LPF and no S&H

Pre-Patching The original Moog System IIIP had internal “trunk lines” that carried external signals from the rear to the front of the cabinets, these were accessed from the CP3 Console Panel. They are labelled as Trunk Lines, and are not replicated in the Behringer module. There were no signal busses that spanned the three cabinets, only the 10-pin power cables. Up to 3 external controllers could be connected to the rear of the right hand cabinet, with the Pitch CV and S-Trig signals available to patch from the CP1 module. The System 55 has inter cabinet busses, as it was not portable.

The Euro Rack standard has no notion of control signals in the 10 pin power connector, and just a single CV and Gate in the 16-pin connector. Behringer System 55 modules do not use a bus concept and only provide external jack sockets, which results in a lot of patch cables. 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.

My objective is to reduce the amount of patch cables by implementing internal patching as on the original Moog. I have replicated the buss structure using 6 way IDC connectors and a bus board and implemented “trunk lines” with Op Amp buffers in the AM- CP3. These modules have been created:

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 least 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 has some custom AMSynths modules added to the Behringer line up to provided more features and a better workflow.

Upgrading Behringer use good quality components but there are some upgrades that are worth making, such as replacing the 50KC and 1MA pots (where they are used right at the end of their travel) and using polypropylene matched capacitors in filter circuits. I have also swapped in expensive multi-turn trimmers (to make adjustment easier). I have not attempted Op Amp upgrades as this may need further circuit changes.

Mods and Extra Modules I have modified some of the Behringer modules and added new ones;

These are explained in the Mods & Modules page here.

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 or three MiniMoogs (for solos) in addition to his ARP white Odyssey, an EMS AKS and an ARP 2600.

My “Big Moog” Setup My Schulze Modular is housed in 3x Doepfer 9U vintage 84HP cabinets; the left cabinet contains the VCO’s and Filters, the middle cabinet the VCA, Env Gens and 984 Mixer and the right cabinet the two 960 Sequencers with 2x 962, a 961, Doepfer Clock Divider and Dual Quantizer. Instead of adding a third bank of 921A/B VCO’s into the middle cabinet I decided to add a Behringer Model D. There is also a replica PPG 313 and 314 Sequencer in the right cabinet.

The cabinets sit on three oak 1U 19″ rack cases (made in France) which contain: Lexicon PCM60 Reverb (replaced by Yamaha SPX990), Alesis Quadraverb and a replica EMS Eight Octave Filter Bank. A black Arturia Key Step is used as the primary keyboard and a Maschine Mikro plays a library of official Klaus Schulze samples.

2022 Update To get close to a Moog Modular IIIP and the KS setup, I made the following changes to my “Big Moog” in the spring of 2022:

  • Model D replaced with bank of AM901A/B VCO’s in cabinet 2.
  • Guin Guin MME added as main Minimoog clone (as a 60HP desktop).
  • Internal patching implemented using a 6-way bus.
  • Cabinet 1 and 2 interconnected using 6-pin DIN cable.
  • AM992 and AM996 modules replace the Behringer 992 and CP3A-O modules.
  • AM-CP4 module added to control a 904A and a pair of 902/911’s in cabinet 2.
  • The wider AM-CP3 modules replace the Behringer CP3A’s.
  • AM904A/B/C modules replace the Behringer 904A/B.

More details of the AMSynths internal bus and connectivity approach are explained here.

Copyright AMSynths 2019