Vintage Synth Explorer

Oberheim • OB-Xa

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!

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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Posting Rules: Please keep your comments relevant! Do not post requests for help, do not use for sales, do not post unless you have something interesting to say about this instrument, or we may delete your post.

 

PoppaNeedsANap

Posted 281 days ago

I'm curious to know more about tweaking the trims ... anyone (ron?) know where I can find out more about this?
I'm a little hesitant to just start jamming away at the trim pots because my OBXa is sweet as is...

Henry

Posted 285 days ago

Just took my OB-Xa from storage and starting working with it, but have a problem as I can't stop it from going through all 8 oscillators in series upon touching any key, any advise?

Chris

Posted 287 days ago

I stuck in your mom's head, Kiernan.

ron

Posted 299 days ago

Just a correction, the obxa has 2 lfo's, not three.One is programmable and the other one is in the modulation section at the bottom left. This synth brings me hours of pleasure, sometimes I could swear it's alive. When I got mine I had to learn how to tune it, and spent a lot of time under the hood. Now I know the voice cards well, and don't hesitate to tweak the trimmers on a voice to give that voice a touch more resonance or envelope modulation or whatever, so that as you cycle through the voices every eighth voice or fourth ( I sometimes kill the bottom 4) you get variation even if you're hitting the same key. Kind of like a four or eight voice, only you have to lift the hood to make changes. Don't be afraid to get in there, you are better off in the end knowing how to fine tune your OB, because as they get older they will need some tweaking. I'll never part with mine, I would swear an oath of vengeance if it was ever stolen.

planetplayer

Posted 313 days ago

Massive brass and poly sounds. It could squirm around like a TB-303also with the potamento on. I remember envolopes are more better that Sequential P5 so sound posiibilities are greater. It is load like a P5, but this sounded to me louder than a P5. If I remember correctly the P5 keyboard action was more sturdy than the OB-XA and was corrected on the OB-8. Nice filters and LFO.
I played this in early 1980s. The Jupiter 8 was quicker to program.
Also, it felt weird turning big knobs on a synth,but I loved it. A deeper angle of the panel may have helped.

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