The renowned Sequential Circuits Prophet-5

Page under construction.
Introduction here. My own studio pictures and patch details to come as soon as possible!

The Sequential Circuits Prophet-5 The Prophet-5 was made by Sequential Circuits Inc. between 1977 and 1984. It was first demonstrated in January 1978 and was on its release "the worlds leading polyphonic synthesizer" according to its manufacturer. This was probably fair since the Prophet's sound, especially that of the early (Revision 1 and 2) instruments is still renowned and sought after today in year 2000. It was really the first 'proper' polyphonic synthesizer, defining properties which are taken for granted in instruments today: it was voice-assignable, each voice with its own filter, amplifier and envelopes; it had memories (40 then later 120) for storing and recalling complete patches (programmed sounds), and later developments included cassette storage and retrieval of patches, control from a remote keyboard or sequencer, and the set-up for MIDI control. The Prophet-5 was a milestone partly because it was a true 'voice-assignable' synthesizer; each of the 5 voices had 2 oscillators and these 5 pairs were all equivalent and essentially 'independent'. Each note played on the keyboard was assigned to one of these voices. Each voice had its own filter with its own ADSR (Attack-Decay-Sustain-Release) envelope, and an amplifier with its own ADSR envelope, which meant both the timbre and loudness could be contoured independently. The circuitry was developed by Dave Rossum's team at Solid State Microtechnologies (SSM) whose leader later founded EMU Systems, and the SSM2040 filter circuit has become renowned among synthesizer fans for its beautiful "so right" sound, which was essential to the Prophet's sonic versatility and appeal as a great-sounding instrument. Essentially, the Prophet was like 5 monophonic synthesizers in a single box, akin to 5 Minimoogs or 5 ARP Odysseys, but not actually the same. Unlike monosynths, a true polysynth needs computer control, and was known as a digital-analog(ue) hybrid. Instead of the controls directly affecting the analogue synthesizer voices, most controls were set up to input 'data' to a microcomputer which had 3 main functions: 1. To scan the keyboard for inputs and to assign a voice to each note played. The computer is needed to handle several simultaneous inputs from the keyboard and to control several sets of voice controls independently according to the programmed parameters in the 'patch', unlike a monosynth, which essentially has one input (a simple voltage from the keyboard whose value is defined by the key pressed - like a simple potentiometer) directly controlling one voice. 2. To store the program settings. 3. To tune the oscillators. Most early polysynths weren't set up like this. The Prophet eschewed shortcuts and 'went for it' - each independent voice was set up like a monosynth, and the overall control was handled by the computer, with the advantage of on-board (non-volatile) memory storage, and the ability to handle external digital control and storage. Almost all Prophets can now take MIDI 'retrofits', which allow a degree of control of the synth (via velocity-sensitive external keyboard for instance, contolling the loudness and filter) not dreamt of by most manufacturers in 1978. Altogether, about 7200 Prophet-5s were made, which fall into 3 main 'revisions' and some sub-categories. There is conflicting information on the exact nature of these modifications now, but here is the best evidence I have found. Prophet-5 revisions: Rev 1 : Ser. No. 0001 - 0182 Earliest Prophet-5s : Koa-wood case (gorgeous), 40 program memories, no cassette interface, won't take MIDI retrofit. SSM oscillators, filters, amplifiers, envelope generators. The earliest had 10 voices (20 oscillators) on 2 circuit boards but due to overheating they were untunable and 5 voices were removed (one voice board - the vacant connection for this 2nd voice board can still be seen). All subsequent models had just the 5 voices. (Does the name 'Prophet-5' come from 5 voices or 5 octaves?) Rev 2 : Ser. No. 0184 - 1299 Similar to Rev 1, but : Walnut case (not quite as gorgeous), 5 voices, 40 program memories. Will take MIDI retrofit - probably because specification was tighter and more consistent. Solid State Microtechnologies (SSM) oscillators, filters, amplifiers, envelope generators. Rev 2.0 : No cassette interface as standard, will take cassette interface as upgrade, will take MIDI retrofit. Rev 2.1 : cassette interface as standard. Rev 2.2 : control panel textured, not smooth (control panel, front brace, bottom assembly and mod box now from different manufacturer, Spacesonic). Rev 3 : Ser. No. 1300 - 7200 Curtis Electro-Music [CEM] oscillators, filters, amplifiers, envelope generators. Quite a radical internal re-design was needed in order to use these more stable and reliable components but the characteristic voice architecture and panel controls remained very similar. Cassette interface as standard and will take MIDI retrofit, but due to the different electronics, they are not the same as those for the Rev 2s! Rev 3.1 Ser. No. 1300-2460 : Rev 3.2 Ser. No. 2461-4063 : Rev 3.3 Ser. No. 4064-7200 :120 Programs Two Prophet-5 images for comparison. The upper image is a later 'CEM' Prophet-5 (Revision 3) The lower image is an early 'SSM' Prophet-5 (Revision 1 or 2) The control layouts are slightly different:

Note the silver volume knob at top right on the early model (below) is moved nearer to the badge on the Rev 3 (left). The Rev 3 also had an A440 switch to generate a 440Hz 'A' tone for tuning, next to the other silver (Master Tune) knob. Dedicated cassette interface controls are visible on the Rev 3, (top right of panel). Two small grey buttons are visible on the early models (panel far left and top centre). These were 'Preset' controls to enable instant editing of mod and filter sections for the selected patch; they also doubled as cassette interface load and save controls. They are not present on the Rev 3. The Rev 3 has its filter knobs in a 'square' formation, whereas the filter knobs on the SSM Prophets are in a 'staggered' formation, because of the extra grey 'Preset' switch on the early models already mentioned (top centre-right of lower image).

The next 4 images are photos of my own beloved Revision 2.0 Prophet-5 from 1979:

My Revision 2.0 Prophet-5 on the living room table. This synth was restored and sold to me on 21 September 1998 by Simon Alexander, who is a Prophet expert in the UK.

The Revision 2.0 P-5 Modulation Controls.

The Revision 2.0 P-5 Filter Controls.

The Revision 2.0 P-5 Amplifier Controls.

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