Oberheim OB-SX

Oberheim OB-SX Image

The OB-SX was envisioned by designers to be a smaller, lighter, more durable "live performance" version of their (then) flagship OB-X. The OB-SX featured the same VCO/VCF/VCAs of the OB-X and a voice card design similar to the OB-Xa in which polyphony was based on the number of 2-voice PCB cards installed (using CEM/Curtis chips). Sacrifices were made to the OB-X's "knob for each function" programming interface (replaced in the "SX" by a few realtime only filter and envelope controls), the ability to save patches (all sounds were preset in ROM) and the last octave of the keyboard ("chopped" to 48 notes).

Despite the sacrifices, the OB-SX faithfully reproduces the character (and at times the "ill temper" of an all analog design) of the OB-X and OB-Xa. The preset sounds are a bit dated (e.g. early funk & late prog rock), but still usable and the realtime controls allow a good amount of "shaping" to be done. It's important to note that like all Oberheim synths, the OB-SX was a continual work in progress and there were many different revisions made to the OB-SX during its life time. Major revisions included: Early units had 24 presets and mid units had 48 presets and late units had 56 presets (later units had a slide switch on the back to change between banks of presets). The color/case design was changed from the (early units) black & gray of the OB-X to the (later units) black & blue pinstripes of the OB-Xa and OB-8.

Early on Oberheim offered OB-SX purchasers the option of sending in cassette dumps of their OB-X patches and burning them into OB-SX ROMs, so there's the possiblity that the presets in an OB-SX may be unique to that specific unit. Somewhere during production the pre-MIDI "Oberheim System" digital interface was added to the OB-SX, allowing the OB-X to interface with the Oberheim DSX sequencer.

Like all early analog synths the OB-SX is vulnerable to voltage and temperature changes (so make sure you allow the unit to fully warm up and use a voltage regulator/battery backup) and some ICs and replacement parts are now extinct - try before you buy!

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5 Visitor comments
August 13, 2012 @ 7:59 am
Great synth. While it might not be as flexible as the OB-XA and OB-X, it's capable of sounds that neither of the other two are capable of, because internally it's a mixture of the two, with architecture from the obx and cem chips from the obxa.
September 14, 2011 @ 2:34 pm
The redstriped OB-SX above is not the original colour. Who owned exactly this serialnumber pictured above, and why was it repainted?
June 14, 2010 @ 5:33 pm
Sounds absolutely amazing, warm and sweet. Too bad that you cannot modify the presets too much. Seems that a lot of these are destroyed by reckless ebayers trying to make a buck by selling the parts(voice cards). SHAME ON THEM!
November 10, 2009 @ 6:43 am
I have a genuine 5 Voice Model, 56 Preset version with the OB-Xa blue striped paint job, produced in Febraury 1982. Mine does not have the slide switch on the rear panel, but does have the blanked off slot where the switch used to go. My model also has CV and Gate In/Out jacks that control voice 1.

The Voice Architecture of the OB-SX is that of the OB-X, but the physical construction is that of the OB-Xa relying on Curtis CEM chips and voice cards instead of the discreet curcuits of the OB-X

Sonically it sounds like an OB-Xa in 2 Pole filter mode, but some sounds demonstrate the OB-X architecture as they have Oscillator Cross Modulation, whereas the OB-Xa uses the Filter Envelope to Modulate the Oscillators.

The OB-SX therefore appears to be a hybrid between the OB-X and OB-Xa, maybe even a proof of concept for switching manufacturing techniques to Curtis chip based voice cards used in the OB-Xa.

Some regard it as a "poor man's OB-Xa"
April 10, 2009 @ 10:05 am
The OB-SX has been used by Charles BErnstein (on the soundtrack to "Nightmare On Elm Street, 1984) and Prince.
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Rated 3.43 (68 Votes)

  • Check Price
  • The link above will take you to an eBay search for this synth to see active listings. If you don't find it there, try looking in our forum marketplace or post a wanted classified.
  • Specifications
  • Polyphony - 2, 4, or 6, voices
  • Oscillators - 2 VCO's
  • LFO - 1 variable from 1/10 osc/sec to 20 osc/sec
  • Filter - VCF with envelope, dedicated cutoff control
  • VCA - ASR Envelope
  • Keyboard - 48 keys
  • Memory - 24 (early units) 48 or 56 (later units) Preset sounds
  • Control - CV/GATE (early units) "Oberheim System" digital interface (later units)
  • Date Produced - 1980 - 1983
  • Resources & Credits
  • Images from Fredric Tirheden, found at Synth Site.

    Additional information provided by Six Steve Six.

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