Oberheim OB-Xa

Oberheim OB-Xa Image

The OB-Xa is a massive analog synthesizer with a very familiar and classic Oberheim sound. Its sound, size and power are very similar to the Prophet 5 from Sequential. However this one has up to 8 voices which can be split, layered and stored!

The OB-Xa was available in four, six or eight voice polyphonic models. They all featured patch memories, also in varying degrees. A minimum of 32 patches were available on early models (4 banks of 8). The maximum amount of patch memory storage found on many OB-Xa's is 120 patch memories. All models of OB-Xa, however, featured the new Curtis chips which offered great stability for an analog synth and they are attributed to its great filters and sounds.

The OB-X was very similar to the OB-Xa except that its voices could not be split or layered and, more significantly, the OB-X had a lowpass-only discrete SEM 12dB/oct state variable filter, which had a great and classic Oberheim sound. The OB-Xa changed that in an attempt to economize manufacturing and increase stability by switching to CEM3320 Curtis chips for its filters. The Xa offered two switchable filter modes: 12 dB/oct (2-pole) or 24 dB/oct (4-pole). This hardware change resulted in a more agressive sound, not quite as creamy as the OBX original, but what still became a "bread and butter" sound of the Oberheim line.

Splitting the keyboard mode separates the OB-Xa into two 4-voice synths with two available patches. The Layer mode plays the two patches simultaneously. There are also some added effect sources, perfect for any analog polysynth, including portamento, unison, sample & hold, chord memory and three LFO's!

Oberheim OB-Xa Image

However none of the original OB-Xa's have MIDI, unless otherwise having been modified. The OB-Xa is a classic and fat analog machine. It will give you thick analog pads and drones, punchy bass and cyclic analog effects. It's been used in the past by Depeche Mode, Van Halen (Jump!), Gary Numan, Jean Michel Jarre, New Order, Paul Sheafer, Prince, Queen, Jethro Tull, Stevie Nicks, Sneaker Pimps, Rush, Mike Oldfield, Richard Barbieri, the Thompson Twins and Bon Jovi.

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41 Visitor comments
March 17, 2011 @ 2:39 am
Fantastic machine ! With incredible sound ! Long time dreamed and now comes reality ;-)
I have the pleasure to have an OB8 and from last week an OB-Xa.
Now I'm searching for a original presets file for my Alzheimer OB-Xa 120 preset to compare my self the difference between this 2 models.
February 13, 2011 @ 6:37 am
Playing one of these is a smile a minute! Although the OB-xa can also do harsh and aggressive, it has its soft side too which is often overlooked. The Pratt & Reed keyboard has nice action and is easy to rebuild, level and drop in new bushings. The factory presets showcases much of what the synth can do especially the 128 program models. Split and stacked presets are limited to 8 memory. The key to the sound is in its tuning instability. It is near impossible to perfectly tune each card; the 'Autotune' calibration only adds to the 'character'. Be prepared to get under the hood if you buy one.
November 18, 2010 @ 3:06 pm
I have all the large Obies, despite the 4 and 8 voice :-( and they are all fantastic.
OB-X, OB-Xa, OB-8, M12, especially the OB-Xa and OB-8
are still very cheap nowadays in my opinion.
Personally i prefer them all over a Jupiter 8, i'll never sell them......so don't bother ;-)
November 12, 2010 @ 3:34 pm
The OB-Xa is a fantastic analog synth. The sound is very different to discrete OB-X, harder and more angry. The OB-X is more lush and warm I like both.
OB-Xa demo: http://www.youtube.com/watch?v=byxQ6aQRGis
BIGGUS [beep] US
June 23, 2010 @ 5:10 pm
Now i know why our OBx and Xa always was out of tune!
Obx 10bit Dac and the Obxa 12bit Dac. Crap!
Xpander 14 + 14 bit scaled auto tempco super range
way below supply noise levels. Superb!
VSE Rating


User Rating

Rated 4.21 (531 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 - 4,6, or 8 voices
  • Oscillators - 2 VCO's per voice - pulse or sawtooth
  • Effects - Portamento, sample & hold, chord memory
  • Filter - 4-pole filter with ADSR envelope and switchable 12dB/oct or 24dB/oct slope
  • VCA - ADSR envelope gen
  • Keyboard - 61 keys
  • Memory - 32 patches (4 banks of 8) to 120 memories
  • Control - Oberheim's 'system'
  • Date Produced - 1981
  • Resources & Credits
  • Images from

    Additional info provided by Tomislav Babic.

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