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.

VISITOR COMMENTS (18)

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BIGGUS [beep] US

Posted 38 days ago

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!

L.V.

Posted 117 days ago

If you're buying one on eBay, always check under the serial number to see how many voices are loaded. There's one on eBay now that's going to sell for an 8-voice price because he doesn't mention it only has 4 (or respond to emails asking). You can just make out "4 voice" on a fuzzy pic of the plate. Someone's going to be very disappointed at the end of this one.

Filip

Posted 158 days ago

Also Simple Minds used this. At least live: http://www.youtube.com/watch?v=7OuZrNbpsSI

McFly

Posted 336 days ago

"I think the early designs - the SEM, the OB-1, the OB-X, and the OB-Xa - have somewhat better sound than the OB-8 and the instruments that followed it. I think that's because the sound of the earlier designs is dirtier in subtle ways, and therefore seems to have more guts. The OB-8 is a more perfect design. The autotune routine tunes the oscillaters more perfectly. But the sound is clean...too clean."

(Tom Oberheim on the Oberheim sound)

Tomislav Babi%u0107

Posted 415 days ago

OB-XA is perfectly stable once u replace all capacitors on voiceboards and PSU. i GIG with mine who problems, its warmup time is less than a minute now.

played the OB-8 many times, and indeed XA is rawer/angry sounding. organic. don't mistake a synth in bad shape that drifts all over the place, with OBXA in full force.. 8 is slightly more polite and uniform. like a missing link btwn XA and XPander.

OBXA is the the only machine ever to feature a LP circuit based on SEM 12dB, yet built round CEM3320. once they got to OB-8 the circuit has changed from SVF - resonance doesnt "sing" or sting that way anymore. XA's 24dB filter is a separate circuit and not as good as 8's.

i use it for hi-reso, lo-cutoff voxy pads drones.. easy to get the VCAs to saturate/break... phenomenal sound. also i use it for vibrato brite strings w trademark "Curtis" sizzle

as w OBX, its not a bad idea to replace vco tune trimmers with multi-turns.

cheers
clusterchord

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