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Oberheim OB-8

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Oberheim OB-8 - Introduction

The Oberheim OB-8, the last fully analog monster Oberheim unleashed onto the synth world in 1983. It's the stuff that big boy analog poly synth dreams are made of. Large in size and made of wood and metal, it begs to be played, tweaked, and listened to wearing a skinny tie, tight pants, and lots of hair. Aquanet helps.

The OB-8 is the final third of Oberheim's assault on the analog poly synth world. It started with the OB X, a fully discrete monster of a synth. The X had a 12dB filter, pulled straight from Oberheim SEM module, and could be configured to be 8 voices. It was the mainstay of post punkers Killing Joke and Richard Barbieri of Japan.

Oberheim followed up the OB X with the OB Xa. This time, they switched the design from discrete circuitry to Curtis chips, like the father of the monster poly synths: the Sequential Circuits Prophet 5. Also different was the color and look of the synth which went from a decidedly 70s industrial design, featuring grayish decals and black wooden end cheeks, to an early 80s midnight blue and black with somewhat unfinished wooden cheeks. This design was carried over to the OB 8, to the point that the XA and the 8 look virtually identical. While the basic voice architecture was nearly identical (including the Curtis chips) there were subtle, under the hood tweaks that made the OB 8 different from its older siblings.


Oberheim OB-8 - Basic Specs

At its core, the OB 8 is an 8 voice analog poly synth whose individual voice consists of two, Curtis chip based voltage controlled oscillators. They are capable of producing saw, square (with pulse width modulation), and triangle waves. Both oscillators can be tuned a semitone at a time individually, but oscillator 2 has a dedicated detune knob, that allows for that warm VCO detune effect we all know and love.

While there are no continuous volume controls for the VCOs themselves, a simple set of buttons allows you to turn VCO 1 on and off, and set VCO 2 either at full or half volume. There is also a noise source, which, like the level of the oscillators, can only be regulated by an on / off button.

The filter of the OB 8 is the same as in the Prophet 5 rev 3, however, here it can be configured between a 12dB or 24dB mode. Unlike the Prophet 5, the OB-8's filters gets fully resonant in the 12dB mode, thus producing a sound very close to it's discrete family member, the 12dB only OB X.


The OB-8 has two analog envelopes and they are the legendary Curtis CEM3310. These are the same envelopes in the Prophet 5 and the Pro One, and when calibrated correctly, will give you the snap you expect from an analog envelope. These envelopes are hardwired two the filter and the amp, but the filter envelope is also used to provide pitch sweeping to the second VCO. This, combined with the handy oscillator sync function, gives you a wide variety of sounds ranging from the classic to the abrasive.

There are two low frequency oscillators on board, but they are very different from each other. The main LFO has a dedicated patching matrix that is programmed via knobs and buttons, and has the ability to provide a multitude of waveforms, including key synced wave shapes. This means it has certain waveforms that will reset their cycle every time the user hits a key. Very handy for faux arpeggios. It is also capable of producing Sample and Hold (random) waveforms.

The second LFO is a somewhat hardwired affair, in that it can only address the pitch of the oscillators and has a single triangular shape. However, it has a couple of tricks up its sleeve. For starters, the rate and amount is fully configurable via two knobs to the left of the keyboard. One of these knobs is a push / pull affair that acts as an on / off switch for the LFO. That means you can decide to kick the LFO in full bore with the pull of a switch and then rapidly kill it off by pushing it back down. Very handy for quick movements and often faster that using the modulation paddle.

The OB-8 is equipped with a very nice full size keyboard (61 keys) and unlike a lot of its peers, has paddles instead of wheels for pitch bending and vibrato effects. There is also a comprehensive arpeggiator on board that has to be synced via a trigger pulse irregardless of the presence of MIDI (more on this later), but it is a fully featured arpeggiator. To the point that the user can program it almost like a step sequencer in one of the arpeggiation modes. This is done by keying in up to 4 note offsets that the arpeggiator will then adhere to in the order programmed. How about up an octave, down a 7th, up 2 octaves, and down a semitone?

There is also a Unison mode, which will turn the already OBese 8 (see what I did there) into a 16 oscillator monster mono.

From the looks of this spec sheet, there isn't a vast difference between the OB-8 and the OBXa and it would appear to be the case if it wasn't for the presence of the Page 2 button ...

Oberheim OB-8 - Feature Details / Architecture

Double tapping the Page 2 button opens the OB-8 up into a mode that the OBXa does not have. This is the major difference between the two synths. Unlike the X and the Xa, the 8 has a digital LFO, but because of this, Page 2 allows the user to apply all kinds of modifiers and wave shaping to the LFO. Do you want to offset the waveform by 180 degrees? You can do it on Page 2. Want to send a waveform into a sample and hold for staircase type modulation? Again, Page 2 allows you to do this. You can do a number of modifications to the LFO as well as several other very handy functions. For starters, you can disable any of the 8 voices, which allows you to have true monophonic (i.e. non-unison) capabilities. You can also program a voice detune function which will slightly detune each voice. This operation works hand in hand with the OB-8's complex processor and tuning routine which, by default, forces a more "dead on" tuning. This is the major complaint against the OB-8: many users, including Tom Oberheim himself, felt that the 8 was too polite compared to the X and the Xa and missed some of the analog offness. This voice detune function helped remedy this, and if you really wanted to, you could push it into complete detune, where individual voices would be way off the target tuning. The one caveat of this option is that you have to save a patch first to enable this function.

However, and directly addressing the general complaint against the OB-8, if the user wanted a more permanent livelier tuning, it is possible to do so via the internal trim pots. Opening the synth up, a user can see two discrete voice boards addressing 4 voices each (for a total of 8). By enabling the calibration procedure, each VCO can be nudged to be slightly more or less out of tune. There are two LEDs that help with this process and they both light up when the tuning is bang on. If you want your OB-8 to sound more like the Xa, simply vary each VCO for each voice to be a little off from the previous. It's amazing what something as simple as subtle tuning can do to liven up the sound!

Oberheim OB-8 - Sound

And what a sound indeed. The OB-8, while not necessarily the most flexible sound design tool in terms of complex sounds (there's no FM or Cross Mod between the oscillators nor filter), is in a class of its own when it comes to melodic sounds. Strings are a thing of beauty and probably it's most valuable asset. They ooze life, warmth and melancholia. The kinds of sounds that early New Wave records and Italo Disco are adorned with. Listen to The Stranglers' "All Roads Lead to Rome", a definitive "1983 Sound" and you're hearing the OB-8.

The OB-8 also records absolutely beautifully. There is not much need for an EQ as it always feels just right in terms of bass and treble. It has a brassy quality to all the sounds it makes, but it is not the modern kind of harsh high end. Instead, it has a particular gentleness to this frequency spectrum that the ear finds particularly pleasing and that leads to less mucking about in the post.

It is also no slouch when it comes to bass and low end sounds. If you need some pedal notes that have attitude, flip it into the 12dB mode and hit a low D to see what I mean. Increasing the resonance in this mode as well will produce a very pleasant self-oscillation that, when combined with the analog envelopes, produces the kinds of filter sweeps dreams are made of.

Oberheim OB-8 - Demo Video

Oberheim OB-8 - Applications in todays world / How it fits in hybrid modern set up / Conclusion

The closest (in terms of new machines) that a person can get to the OB-8 is - oddly enough - the Dave Smith Instruments Prophet 08. Take a listen to the comparison video below and you'll see there are striking similarities in the tone color. However, the liveliness and organic vibe of the OB-8 is just not present here. You're in the ball park, but it's the difference between playing the game, and watching it. And because the OB-8, with minor maintenance, is the most stable of the OB range, if you have to have that definitive Oberheim tone, it is your best bet. Not to mention the fact that most OB-8's were modded with factory MIDI. From my best understanding, the early ones did not have MIDI but were updated with a retrofit straight from Oberheim. You'll know if your OB-8 is one of these, because the MIDI ports will be recessed into the left wooden end cheek. If, they're on the back panel along with all the connectors, then your OB-8 came straight off the assembly line with MIDI. Also, don't let the size of the synth fool you, as it is surprisingly light and takes no more than removing 8 screws to get to the insides for fast repairing!

Review by Matia of INHALT




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