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.

ron

April 9, 2009 @ 12:45 am

poppaneedsanap... You can find the service manual online, in it you will see where the trimmers are located. I believe it's one of the last pages? trimmers are labeled. I should warn you, it takes a little time to get all of the voices the same again, but fortunately the procedure is in the service manual and does not require special equipment. Having said that, once you get familiar with the voice cards it's no big deal, and not scary. Like I said, I had to figure out how to tune it, and did so before I had a manual, just from twiddling. But now the machine is more personal, if that counts for anything.

allan

February 23, 2009 @ 3:37 am

contrary to belief it was a obx through a marshall stack that was used
on van halens jump , not a obxa as in the video, definately superior to
any oberheim released after

Matruxman

February 21, 2009 @ 12:48 am

It lacks proper MIDI (even with retrofit), so I couldn't use computer patch editor that works fine with OB8.
Compared to OB8, oscilators drift alot and that make illusion that synth is rawer, but that 'gift' is not something I very much appreciated by OBXa.
Replacing it by OB8 resolved several key issues incl. important one reliability.
OBXa also lacks some important functions of OB8, so if choice is there opting for OB8 seems as clear choice.

PoppaNeedsANap

February 13, 2009 @ 6:00 pm

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...

ron

January 26, 2009 @ 2:17 pm

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.

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