MuTe/YLE Serge Modular

Date: 26.6.2025

Here are some details about the Serge modular system owned by the Department of Music Technology (MuTe) at the Sibelius Academy, University of the Arts Helsinki. I have had the pleasure of servicing it on a few occasions over the past couple of years.

This instrument was acquired by the Finnish Broadcasting Company Yleisradio (YLE) around 1981-82 [3]. The ordering and design of the actual configuration were handled by Andrew Bentley, who was working at the YLE Experimental Studio, where the instrument was located after it was assembled from kits. It remained in use at YLE for many years until it was donated to MuTe in 2012 [5].

The system consists of three racks. Two of the racks are custom configurations, each containing four 19-inch panels. The third rack is a standard Series ’79. The lowest panel on the first rack is a fully custom setup made at YLE, while all the remaining panels are stock Serge modules, PCBs assembled in early 1981. The only exceptions are the BUS and PATCH portions, which are unbuffered interconnection patch bays. These allow distributed patching if racks are placed apart from each other. Longish DB25 cable is used to connect these sections together.

Full list of the modules:

  • Rack 1:
    • Panel 1 (top):
      • Pitch and Envelope Follower
      • NTO (New Timbral Oscillator)
      • NTO
      • NTO
    • Panel 2:
      • Bus (interconnect patch panel)
      • SSG (Smooth and Stepped Function Generator)
      • Dual Analog Shift Register
      • Triple Comparator
      • PCO (Precision VCO)
      • PCO
      • NTO
    • Panel 3:
      • Patch (interconnect patch panel)
      • Noise Source
      • Dual Random Generator
      • PRC (Dual Processor)
      • PRC
      • DSG (Dual Universal Slope Generator)
      • DSG
    • Panel 4:
      • Custom YLE IXTAL interface
  • Rack 2:
    • Panel 1:
      • VCF2 (Variable Bandwidth Filter)
      • VCFQ (Extended Range Filter)
      • VCFQ
      • ACPR (Active Prosess’r)
      • ACPR
      • Quad VCA
      • Universal Equal Power Active Processor
    • Panel 2:
      • VCF2
      • VCFQ
      • VCFQ
      • ADSR (Extended ADSR)
      • ADSR
      • ADSR
      • ADSR
      • Bus (interconnect patch panel)
    • Panel 3:
      • TWS (Triple Waveshaper)
      • VCM (Wave Multiplier)
      • Ring (R6) (Ring Modulator)
      • Ring (R6) VCA
      • ADSR
      • ADSR
      • Triple Bi-Directional Router
      • Ten-Stage Pulse Sequencer
      • Patch (interconnect patch panel)
    • Panel 4:
      • 2PHA (Dual Phaser)
      • RES (Resonant Equalizer)
      • MAX (Matrix Mixer)
      • MIX2 (Dual Audio Mixer)
      • MIX2
  • Rack 3 is a stock Series 79:
    • Panel 1:
      • SSG
      • Noise Source
      • PRC
      • DSG
      • Phaser
      • Universal Equal Power Audio Processor
    • Panel 2:
      • NTO
      • PCO
      • PCO
      • VCM
      • Variable Q VCF
      • Dual Transient Generator
      • MIX2
    • Panel 3:
      • Touch Activated Keyboard Sequencer (115B)

IXTLAN

The fourth panel, labeled IXTLAN on rack 1, is fully custom. It features connections to a computer interface, an external IXTLAN mixer, two CV joysticks, a tuner, and connections for an oscilloscope, the main PA, an external CV keyboard (possibly Roland 100m 184), and a D109 (whatever that may be).

Joysticks are standard CV joysticks that, in addition to X and Y outputs (ranging from -5V to +5V), feature additional outputs labeled A, B, C, and D. Although the letters are positioned at the corners of the joysticks on the panel, each output actually corresponds to a specific edge. The output voltages are derived from the signals X and Y as follows: max(X, 0), max(-X, 0), max(Y, 0), and max(-Y, 0) (I have to check which output is which).

The music system is jacks are wired directly to the main output RCA jacks located at the back of the unit. Similarly, the oscilloscope jacks are connected directly to the BNC jacks at the rear of the unit.

The tuner is a guitar tuning device that has been disassembled and integrated into the panel. I believe it is a Seiko ST-369, but I’m not 100% sure. It features an oscillator output for tuning reference, as well as line and microphone inputs.

ADC and DAC jacks are used to interface a synthesizer with an Apple II computer equipped with an 8-bit Mountain Computer A/D and D/A card [1]. The rack contains level-shifting buffers that convert the [-5V, +5V] range of the A/D card to the [0V, +5V] range used by Serge. Bentley developed software called SYNTHEX [2] for the Apple II, which is used to manipulate and generate control voltage (CV) signals. If my calculations are correct, the computer should be able to process all 16 channels at a sample rate of approximately 2500 Hz. I do not know the whereabouts of the Apple II computer used with synthesizer.

IN, OUT, and CON connections are wired to an external mixer that features 16 channels. The CON serves as a control voltage input for VCA on each channel strip [4]. I do not have a picture of the mixer at the moment, but I hope to provide one soon.

BUS connections are wired to the BUS panels on racks 1 and 2. It is unclear whether these jacks should be connected to an external device, as there is also a spare socket located at the back of the unit.

D109 socket located at the back of the unit appears to be connected to the PULSE send/return jacks.

There is a socket labeled VOCODER at the back as well. This socket is connected to the level-shifting circuits, but I haven’t checked the specifics of the wiring. It doesn’t seem to be connected to panel jacks.

References

  1. Mountain Computer Inc. 1981. A/D+D/A Operating Manual.
  2. Bentley, Andrew. THE SYNTHEX PROGRAMME MANUAL. Unreleased.
  3. Bentley, Andrew. 1982. Serge Modular Music Systems, Experimental Studio Custom Synthesizer and Series 79′. Unreleased.
  4. Bentley, Andrew (?). [Simplified User manual in Finnish]. Unreleased.
  5. YLE. 2012. Klassinen: Serge muutti Sibelius-Akatemiaan.

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