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Saturday, December 15th, 2018 03:16 am

Synth Glossary

Physical Modelling:
Physical modelling is a method of synthesis in which a mathematical model of the instrument being synthesized is used to create the sound. It is the best way of approximating a real instrument....

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OB-8
The OB-8 featured 8-voice polyphony, a VCF that was switchable between 2-pole and 4-pole, and the Oberheim "parallel buss" system which allowed it to interface with the DMX drum machine and the DSX digital sequencer.

"Oberheim's OB Series instruments, including the OB-X, OB-Xa and OB-SX were, if not the foundations, certainly the walls on which the company was built. This was Oberheim's high spot, its heyday. And the OB-8 was the last of the series. OB synths all have a certain warmth and richness, and although Tom Oberheim himself has gone on record as saying he feels that the OB-8 is "too perfect" (well!) and lacks the grit of the earlier models this is still a very human-sounding instrument. These synths were all embraced by the R&B and dance merchants.

"The OB-8 has two VCOs per voice, each with sawtooth, pulse and triangle waveforms. Oscillators can be tuned separately and then shackled together in hard sync for searing, hollow lead line sounds. The OB-8 departs somewhat from the earlier OB designs in its filter section, offering a choice of two-pole or the more drastic four-pole filter slopes. An ADSR envelope generator is reserved for the filter. The filter is certainly precise, which probably accounts for Tom Oberheim's slight retrospective misgivings on the instrument.

"LFO modulation can be in triangle, square, positive or negative ramp or sample-and- hold waveshapes and can be used to modulate VCO frequency or pulse width, the VCF cutoff frequency or the VCA. Deeper into the programming pages, you'll find additional LFO functions for changing the LFO sweep to half-steps and "unsyncing" the LFO for out-of-phase effects.

"The LFO can also effectively track the keyboard and thus speed up as you play higher and higher. Portamento options of smooth or quantized travel and even polyphonic portamento are also found here. Plenty of neat tricks and a taste of things to come, when Oberheim went fully modulation-crazy on the Matrix-12 and the Xpander. "Here on the OB-8, Oberheim (rightly) felt that such in-depth features could frighten off the prospective programmer and so hid these advanced features in a "Page 2" mode. This mode simply activates a second set of programming parameters under the control of the regular panel knobs and switches once you double-press the Page 2/Chord button. The nervous could then, and probably most often did, avoid the heavy programming stuff and just get on with the playing. The Page 2 concept caught on to such an extent that it somewhat rebounded on Oberheim, which subsequently had to offer a new front-panel screen which signposted these secondary, hidden functions. Oberheim charged $150 for this "upgrade," says synth guru and OB-8 owner Craig Anderton, who decided to forgo the charge in favor of memorizing the commands. Now, he says, not a little bemused, he has a more collectible unit because of it. "The OB-8 came out on the cusp of MIDI -- just before it, in fact -- and so MIDI was offered as a retrofit; it became standard from software revision D onwards. It was obviously a bit of a rush job, since even the official MIDI version can only communicate on channels 1-9, with just program, program dump and lever information being transmitted (in addition to note data, of course). A ray of sunshine here is that in split mode, two sounds will send out on separate channels.

"Patches come in either single or doubled/layered mode, with internal storage for 120 of the former and 24 of the latter. A cassette interface was the original method of external patch storage, though the MIDI iersion does allow patch data to be dumped and loaded also.

"The OB-8 represents a good blend of a player's and a programmer's instrument. The flipper-type pitch and mod wheel isn't to everyone's liking, true, but the keyboard is firm and the sounds feel playable. And there's a highly groovy arpeggiator that can be clocked externally (via arpeggiator clock input jack, thus probably not directly via MIDI) if need be.

"The OB-8 was the hub of Oberheim's "System," comprising the OB-8 keyboard, DMX drum machine and DSX sequencer. It was quite the system to have for a brief period, until MIDI arrived and blew the need for such restricted practices to smithereens. You don't buy Oberheim synths for precision accuracy and reliability, but the OB-8 was by far the most stable of the OB range and, when it did go out, the easiest to service."

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