This keyboard is an early Oberheim preset analog beast. I'm not sure when it came out but it looks like it probably came out after the white face 4 and 6 voice models but before the OB8 and OBX which added the blue on the black casing.
The OBSX uses pure VCO's instead of DCO's which tend to through it out of tune now and then, but fortunately it has an autotune button to throw it back in tune. I have an OBSX with 4 voices, but one of the voice cards refused to stay in tune, so I had to turn it off. A cool thing about the OBSX is that if you can find any, you can easily install up to six total voice cards simply by popping the cover off and inserting the cards in. Each voice card is about 8 by 4 inches. Pretty cool considering today all 6 voices would probalby fit in a tiny chip. As far as sound, the OBSX is pure Oberheim, analog bliss. You can get some increadibly fat undertones that will literally make you room shake.
I have a Matrix6 as well, but the Matrix6 ! can't create the same low rumble I'm refering to. On the down side you can't save any presets, which isn't too bad considering many synths of this date couldn't anyway, and you have limitted tweaking control of the sounds. Your limitted to 7 knobs consisting of: Portomento, LFO Rate, OSC 2 Detune, Filter Frequency, Amp & Filter Attack, Filter Decay, and Amplifier Release. There are for buttons to put the keyboard into Auto, Hold, Chord, and Unison mode. Auto is default freeplay mode if you're wondering. There are three bank of 16 sounds for a total of 48 presets that are easily selected by pressing the standard Oberheim buttons found on the OBX line. I got mine for $225 US from an add in the paper. For that price I donot regret it one bit.
If you can find one for under $350 or so, I'd say go for it. I've seen them from $200 to $250. This synth has the deapest bass drones I've heard period. I literally got my room to start rumbling with this one.
Released: Late 70s? | 
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