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Cleveland Yard South Group

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Richard Alekseev
Richard Alekseev

Project: ETI Vocoder - Front Panel Manufacture

The Audio Input path functions similarly using U1-D and U1-C. The output of U1-C (Audio Input path buffer) is applied to both the AUD bus, which applies the audio signal to the audio signal path's bandpass filter inputs, and the Audio Mix-In Level pot. You can apply a portion of the Audio Signal to the output if desired. Doing so allows both the vocoded audio and the raw audio to be mixed to the output. U2-A (1/2 TL072CN) is the vocoder's output buffer. All of the vocoder's band pass channels feed the inverting input of U2-A which acts as the circuit's main mixer. U2-A's output is fed to Output Level pot R4 whose wiper feeds the output jack via 1uF non-polarized cap C3 in series with 100 ohm resistor R9. NOTE: C3 (1uF bipolar cap) and R9 (100 ohm resistor) are not located on the circuit board but are installed on the unit's front panel.

Project: ETI Vocoder - Front Panel Manufacture


Hardware offerings range from complete systems in cases to kits for hobbyists. Many manufacturers augment their range with products based on recent re-designs of classic modules; often both the original and subsequent reworked designs are available free on the Internet, the original patents having lapsed. Many hobbyist designers also make available bare PCB boards and front panels for sale to other hobbyists.

Two 3U unit standards, in particular, are notable: Frac Rack (e.g., PAiA), which uses the entire 3U for the front panel, and Eurorack (e.g., Doepfer) which has a 2 mm horizontal lip that the front panels are seated between. Further minor variations exist where European or Japanese manufacturers round a U measurement up or down to some closer convenient metric equivalent; for example, the common 5U modules are exactly 8.75 inches (222.25 mm), but non-American manufacturers may prefer 220 or 230 mm.

One day when I find a bit of time I will redo the frontpanel graphics which I made with clear self adhesive dymo prints and change them against some Lazertran printed decals which will probably look better.

  • Polyphonic 49-note pressure-sensitive synthesiser. 1979 - c.'81.Original price: 800 then 990 then 1491.Target price: 100 - 300Only 50 or so ever made.

  • Colour-coded front panel - extremely bright primary colours. Lots of pretty red, yellow or green LEDs.

  • Whole keyboard tends to lurch when you press down for pressure-sensitivity.

  • Full polyphony, but only one filter.

  • VCOs, two VCLFOs, two ADSR envelopes, filter switchable to 12dB or 24dB.

  • White noise; external input; envelope follower.

  • Analogue chorus/danger/delay line - with time parameter under voltage control.

  • Optional polyphonic sequencer was claimed to provided ten minutes' worth of music, with transposition, editing, storage of VCF voltages, etc. Never appeared commercially, but it was up and running at the launch of the Polysynthi, and at the Frankfurt Show 1979. Possibly the first polyphonic sequencer ever.



Since we get flack for listing for or prices in the Facebook...


  • Mary McCarter
    Mary McCarter
  • Dylan King
    Dylan King
  • Eli Adams
    Eli Adams
  • Richard Alekseev
    Richard Alekseev
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