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Oberheim OB8

8-Voice Polyphonic Synthesiser

The most recent polyphonic synth from Oberheim, the OB8 adds even more flexibility to the tried and tested Oberheim formula.


The heritage of previous polyphonics shows clearly in this latest synthesiser from the Oberheim stable. Not only has it retained the basic look of it's predecessors (keeping a strong product identity with the blue 'executive' styling) but it has retained the fundamental voice format which has made the OB range so popular. Anyone familiar with the OB-X or OB-Xa will automatically feel at home with much of the OB-8 panel. Features have been added without taking away or rearranging any of the familiar 'basics'.


This means that each of the eight voices has 2 VCOs, 2 ADSRs, a selectable 12/24db Low Pass Filter and there are now 3 LFOs to play with. Clever use of button combinations increases the number of VCO and LFO waveforms available and the number of voicing programs (now 120) which the machine can hold at any one time.

Oscillators



The two VCOs still have their individual pitch determined by Frequency knobs which are stepped in semi-tones. Fine Detunes between the oscillators (for fuller sound textures) are still set up on a separate knob, which is very handy for small adjustments. There are now three waveforms available on each oscillator. Besides Sawtooth and Pulse, there is now triangle wave (a purer thinner sound) which is selected by holding down the switches for the other two waveforms simultaneously. The pulse width of both oscillators is controlled from the one knob so different widths cannot be set up on each oscillator.

Oscillators, Filter and Programmer.


The other limiting feature of the Oberheim way of doing things is there is little or no ability to mix sound sources. VCO1 is either on or off, as is the Noise Source and even VCO2 is only available On, ½ volume or Off. However, in compensation there are the very useful features of Sync between the oscillators (for those Jan Hammer sounds) and filter envelope control of VCO 2 pitch (for syndrums, bends, etc).

Filter



The OB Filter configuration is very nice allowing switching between 2 and 4 pole filtering (give a 12 and 24db/octave filter cutoff response) and there is of course an independant ADSR for the filter, totally separate from the amplifier envelope. Whilst the filter can be made to track the keyboard (keeping the same harmonic content to each note), the effect cannot be adjusted unfortunately: again it is either on or off.

Envelope Controls.


The LFO Modulation section has been expanded to allow modulation of the Volume as well as the Pulse Width of either oscillator (or both), with one Depth of modulation, whilst the Pitch and Filter can be modulated with a different mod amount. However, only one Rate and Waveform can be programmed at any one time. The choice of LFO waveforms has now been expanded from just Sine, Square and S/H (Sample and Hold ie. random) to include rising and falling Ramp and all these can now be retriggered from the keyboard.

The Master Control Section has changed very little. Master Volume is still there but the Balance knob (between split and doubled programs) has now become the means of programming individual volumes for each program and also balances between programs in the Split/Double memories. This means that a complete set up of the machine can be selected by pressing two switches and once split or double has been selected you can step through your twelve programs using a footswitch into the Program Advance socket on the back.

(Click image for higher resolution version)


Auto-tune, Master Tune and Hold controls are unchanged but the Chord buffer switch (for memorising a chord to be played from a single note) now doubles as the switch for calling up Page 2 functions (by pressing it twice).

Page Two



This is a clever way of enabling an entire new set of parameters to be programed without the extra expense of the knobs and switches to access them and is the biggest innovation on the OB-8. Over half of the front panel controls are assigned a new function in the Page Two mode.

Master, Control and Modulation Sections.


The diagram below shows which of the control functions change when Page Two has been selected. Let us go through these functions and see just how they operate. Firstly when you select the Page Two 'mode', the programmer switches 1 to 8 light up, showing that all 8 of the synthesiser voice channels are enabled. Pressing any of these switches will cause that channel to be muted (ie. made unavailable for playing with). Programs will now be played with the remaining available voices. This feature is particularly useful if one of the voice channels ceases to operate properly as you can remove it completely until such time as you can have the machine overhauled. Nothing is more irritating than a poly synth with just one oscillator not working, because it usually means that the machine is unplayable as, after every 6 or 8 notes the cycling brings back that oscillator and a note is either missed or sounds wrong. With the OB-8 you can avoid this infuriating state of affairs. Of course this feature can also be used constructively if you want just one channel working - a sound used like this has a much more subtle quality than using the 'unison' switch which gets all sixteen oscillators working monophonically.

The Portamento, which appears as just an 'amount' control on Page One, becomes much more controllable using Page Two. Normally all the voices glide at slightly different rates. However, if you select Match, then all the voices are forced to glide at the same 'matched' speed. The Portamento is normally a smooth glide but by using Quantize you can change this into semi-tones ie. glissando, so only the musical pitch intervals are played in the course of a glide. Portamento Bend is a particularly interesting feature; this allows you to program an interval above or below a note, and each time the note is triggered the pitch is forced to glide from this interval either up or down to the 'played' note. This feature, more controllable than Portamento, is in fact true Glide and allows precise effects to be programmed, irrespective of the notes played.

Left-hand panel with levers and arpeggiator.


LFO Controls



The additional control that Page Two gives you over the LFO is nothing if not complete. Again, the effect can be quantized on either of the modulation routings and the depth of the steps set by the Mod Depth knobs. This allows you to get rhythmic effects is a similar way to Sample and Hold, but with a regular pattern to them. This is made all the more effective by the fact that you can set the point at which any of the waveforms is retriggered by the keyboard (using Trig Point, which replaces Filter in Page Two).

Page Two also provides two simple envelopes for the LFO, one for each modulation depth. These envelopes consist of a Delay time (which holds off the modulation) and an Attack time (which controls the introduction of the modulation). If either of these controls is used, then when a new note is played the modulation is instantly reduced to zero and re-introduced according to the settings of these controls. Of course this makes highly desirable musical effects such as delay vibrato programmable and automatic whereas on previous OB models they had to be introduced by the Mod lever. Even more complex effects can be introduced by using the Invert control on each Mod. Envelope. This means that the mod is there as soon as the note is played, continues for the programmed Delay time and then disappears at the rate set by the Attack Mod control.

Voice Panning Presets.

LFO Track causes the LFO speed to be modified by the pitch of the note played, by adding the keyboard control voltage to the LFO rate control voltage. In practice this means that the higher up the keyboard you go the faster the modulation rate. The speed of the LFO can also be controlled by the second Mod envelope. This means that you can start with a slower mod and after the Delay Mod 2 time, increase the speed using the Attack Mod 2 control (useful for imitating Leslie speakers). Conversely the use of Invert 2 allows the speed of the LFO to be decreased after a programmable time.

The final Page Two control adds an extra feature which I have always wanted to see on synths with a 'Unison' capability. Using the Osc 2 Detune control you can actually detune the voices (all 8 of them) against each other when 'Unison' has been selected. This has to be the ultimate 'fat' lead or bass sound, with unbelievable thickness and punch. In fact, nearly all the Page Two controls make the 'Unison' mode a much more versatile and exciting setting as the numerous modulations can still be accessed: all the voices do not have to be identically programmed.

Back Panel Sockets with Computer Interface 16-pin connector.


Programmer



This has the capacity to memorise all of the main panel settings (Pages 1 & 2) in 120 locations, of which 108 are supplied with factory sounds in them. There are 15 banks of 8 programs on the programmer. The programs in each bank are selected by 8 individual switches, and it is these which change when Program Advance is activated by a footswitch. The 15 banks are slightly more complicated. Four switches labelled A, B, C and D are used in combination, to obtain the 15 possible permutations: A, B, C, D, AB, AC, AD, BC, BD, CD, ABC, ABD, ACD, BCD, ABDC. Each of these then become the name of a bank, so you refer to a program as BD5, ACD7 or B3. This means that whereas changes within a bank are quickly achieved (as with the first four banks), when you are trying to quickly change the later banks you can easily make a mistake and have to try several times. Still if this is a cheap way to access 120 programs (as opposed to 10 banks with a switch each of 12 programs - 22 switches instead of 12) then the greater good must be kept in mind.

The 12 switches also indicate which of the double or split programs have been selected (only one of the twelve switches, A-D or 1-8 is lit at any one time in Split or Double). These enable you to double any two programs (making the OB-8 4-voice poly with two sounds per voice) or split the keyboard at any point and have a different 4-voice program on either side. Twelve double set-ups and 12 split set-ups (including split point) can be stored and recalled. However, the Lower or Upper programs can be substituted at any time, and the 12 set-ups of either type can be stepped through with a footswitch.

The OB-8 opened up.


Left-Hand Panel



Another area where the possibilities of the OB-8 have been enormously expanded is in the Real Time Performance controls to the left of the keyboard. The Bend lever is now programmable, ie. the interval which it operates over can be varied and memorised. And now it is possible to program the lever (which traditionally was pulled towards you for 'up') to operate either way.

This panel now also houses a third LFO which is introduced by the Mod lever. It is quite common for such additional LFOs to be triangle or sine wave only but not this one. By a series of clever combinations of switches and lever positions (admittedly fairly complex) the mod lever can introduce triangle, square, S/H, rising and falling ramp wave and noise generated modulations. The lever can also be bypassed and the mod introduced from a depth knob (on this panel) or a pedal. The modulation thus derived can be routed to the pitch of either VCO or both, and this in turn can be used on either half of a split/double program (particularly useful in conjunction with the hold setting).

Master Control Board.


Arpeggiator



All the controls on this panel also double as the programming switches for the 'intelligent' arpeggiator when you change the mode from Modulation to Arpeggiator. This is far more than the standard arpeggiator which is included in most synths these days. Besides running up, down, or up and down, the order of notes can also be assigned by the order in which they are played on the keyboard, which starts to approach the flexibility of a sequencer. Add to this the fact that the sequence of notes played can be held and then put through a sequence of transpositions which can be programmed or transposed manually. Other possible assignments of the arpeggiator include random order (but with the emphasis on the lowest note), and arpeggiating chords (which, run slowly, gives you a chordal accompaniment). The arpeggiator can of course be triggered externally which increases the sequencing possibilities.

Panning Controls



Hidden in a recess on the right hand cheek are eight panning presets which govern the stereo position of each voice channel. By putting 1-4 over to one side and 5-8 to the other it is possible to have complete separation of Split/Double programs for individual processing of the signals, but a broad stereo picture can also be set-up by a gradual left to right panning from 1-8. This is a very handy feature, but it is a shame that these presets cannot be set up as part of the patch. As a Page Two function that would be a real boon!

Voice Boards (1-4) with (5-8) underneath.


Back Panel



At the far left there are the three audio outputs. Mono, Left and Right Stereo, which give the outputs set by the panning presets. Next along is the Memory Protect switch, which prevents your valuable sounds from being accidentally erased. Just behind this are the three mini-jack sockets for the cassette interface along with the Enable switch. The Oberheim cassette interface system is very versatile with selective loading and saving if required, this means you don't have to go through 120 memories to save or load one particular sound; it can be done in banks of 8. Below this is the computer interface which allows the OB-8 to be connected into the 'system' via the DSX (see accompanying feature).

Foot Switches



A whole host of parameters can be accessed with foot controllers via the jack sockets on the back panel. Switches can be used to enable the sustain and hold features and to advance the sound programs. Pedals allow the introduction of the mod set up on the left-hand panel controlling pitch (Vibrato), and the Filter to be swept, with the Volume controlled by similar means.


The final jack on the back panel accepts the Arpeggiator Clock In to sync it with drum machines or a tape click track.

Internal Construction



Being firmly in the age of the microchip, it comes as no real surprise when the OB-8 is opened up (which is easily achieved by taking out a couple of screws and lifting back the hinged panel) that the internal design is very economical. Two connected boards receive the programming instructions from the front panel, which are passed on by ribbon cable to the master control board. This is based round a central Z80 processor which performs all the control functions. The control instructions from the real time programming panel to the left of the keyboard arrive via a ribbon controller and then instructions are passed on by the same means to the two voice boards, the upper one containing voices 1-4, the lower one voices 5-8. The panning presets are cleverly mounted at the far end of the voice boards to protrude through the wooden side panel. The synthesiser chips used are principally Curtis and each voice is based around the 3340 oscillators. The filters are the CEM 3320 and the envelope generators are the CEM 3310.

Conclusion



Whilst retaining the basic Oberheim programming approach (with all its good points and its faults) so that any previous Oberheim user will feel instantly at home, the OB-8 adds a wealth of subtlety and versatility to the Oberheim arsenal. In particular the new-found all-encompassing flexibility of the LFOs, the 'intelligent' arpeggiator and portamento, and the performance controls make this a real step forward. Page Two adds a wealth of extra programming options without the additional cost of hardware (knobs, switches, etc) as does the left-hand panel. All this adds up to an instrument which is exceptional value for money and must be one of the most versatile synths on the market.

However, amongst all these features and options, it has been very easy to forget to talk about the sound of the instrument. Well, rest assured that the Oberheim sound is as good as ever and only benefits from the extra programming possibilities. The 108 factory presets which come with the OB-8 show its versatility without ever making themselves sound weak or unusable and an accompanying cassette allows you to reload them should you overwrite them with new sounds. All in all a great up-date of a classic range.

Thanks to the London Rock Shop for the loan of the OB-8 for review. The RRP of the OB-8 is £2,995 and it can be seen at the London Rock Shop and Chase Musicians.


Also featuring gear in this article

Patchwork
(EMM Feb 84)


Browse category: Synthesizer > Oberheim



Previous Article in this issue

Danse Electronique

Next article in this issue

Using Sequencers


Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Jan 1984

Donated & scanned by: Stewart Lawler

Gear in this article:

Synthesizer > Oberheim > OB8


Gear Tags:

Analog Synth
Polysynth

Review by Paul Wiffen

Previous article in this issue:

> Danse Electronique

Next article in this issue:

> Using Sequencers


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