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.

mark weisz

June 19, 2011 @ 5:10 pm

One of the boards I used in my rack in the 80's was an OBXA, I absolutely loved it. I since have honed down back to the B3 only but I wish I had it now just cuz. The only problem I had live was occasionally auto tune wouldn't do it all and I would have to open it up between sets and reseat all the IC chips with my finger, it always worked. A pain, but it was so fat!!

johannes

June 8, 2011 @ 11:49 pm

Lets not forget that this montster was all over Cyndi Laupers Mega Hit Record "She's So Unusual"
And Laurie Andersons intricate "Big Science" OB-Xa = Classic, Beautifully Sounding Polysynth this is to be sure...~ Hopefully I will be playing one before too long as I believe its right up there with the Prophet 5s and Jupiter 8s...

James

May 8, 2011 @ 10:13 am

Another 1984 interview with EVH mentiond that he did have an Ob8 during the recording of 1984 but that he preferred the warmer sound of the Ob-xa. He goes on to mention that his Xa was out for repair during the session for tuning issues. Not sure if the Ob8 made it on 1984 but I would not be surprised a few small parts and overdubs were the ob8. "I'll Wait" was a factory obxa patch and "1984" was patches c3 and c4 split. Jump was a tweaked version of patch A1 with dual saw's and cutoff/resonance tuned to taste. The key to the Ob-xa sound is the slight tuning instability between the oscillators

mcfly

May 6, 2011 @ 3:32 am

The patchbook with the 120 patches in high quality PDF and JPG:
http://www.electrongate.com/obfiles/OB-Xa/patchbook.html

mcfly

April 28, 2011 @ 11:02 pm

In the April '84 issue of "Keyboard" Eddie Van Halen says that on the studio recording, he used the OB-Xa in split-mode for both "1984" and "I'll wait". On "Jump" and "1984" the OB-Xa was recorded direct in stereo through a chain of various effects whereas on "I'll wait" (for which he wanted a nastier synth sound) it was recorded through a couple of Music Man amps.

The article also mentions that for the tour Eddie used two OB8's instead of the OB-Xa.

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