Sequential Circuits Prophet-5: Difference between revisions

[[File:Sequential Circuits Prophet-5 Rev 3.3.jpg|thumb|right|400px|Sequential Circuits Prophet-5 Rev 3.3]]The '''Sequential Circuits Prophet-5''' released in 1978, was the first completely programmable [[polyphony|polyphonic]] [[analog]] synthesizer. [[Dave Smith]] designed the electronics and coded the firmware.<ref name="oman">''[http://www.synthfool.com/docs/SequentialCircuits/Prophet_Series/Sequential%20Circuits%20Prophet%205%20Owners%20Manual.pdf Prophet-5 Synthesizer Operation Manual]'' by Stanley Jungleib, Synthfool.com</ref><ref name="vail">''Vintage Synthesizers'' by Mark Vail, Miller Freeman, 1993, ISBN 0-87930-603-3, pp. 173-177</ref><ref name="ko">''Keyfax Omnibus'' by Julian Colbeck, MixBooks, 1996, ISBN 0-918371-08-2, pp. 122-124</ref><ref>[https://www.davesmithinstruments.com/about/ About], Dave Smith Instruments</ref>

 

The Prophet-5 is five voice [[subtractive synthesizer]]. Each voice is an individual synthesizer with two [[VCO]]s (voltage controlled oscillators) osc A and osc B, a [[mixer]], a 24dB per octave four pole resonant low-pass [[VCF]] (voltage controlled filter) controlled by an ADSR [[envelope generator|EG]] (envelope generator) and a final [[VCA]] (voltage controlled amplifier) controlled by another ADSR EG. It also has a single [[LFO]] (low frequency oscillator) and pink noise source.<ref name="techman">''[http://www.synthfool.com/docs/SequentialCircuits/Prophet_Series/Sequential%20Circuits%20Prophet%205%20Technical%20Manual.pdf Sequential Circuits Prophet 5 Technical Manual]'' by Stanley Jungleib, Synthfool.com, s. 2.2</ref><ref name="mbll">[http://web.archive.org/web/20060910020427/http://users.adelphia.net/~cygnusx_1/prophet5.html Prophet 5 Synthesizer] by Matt Bassett</ref>

 

The filter EG modifies the voice [[timbre]] and may also serve as a sound source. The VCA EG shapes the voice [[amplitude]]. The voices are summed together with a single white noise source. With a keystroke a voice is gated to trigger its two EGs.<ref name="techman"/><ref name="mbll"/>

 

 

The Prophet 5 sustained six revs before Sequential Circuits, Inc., was sold to Yamaha in 1987. Rev 2 was a refinement of the Rev 1 models and largely transparent. Rev 3, however, was a redesign. Introduced were new voltage controlled IC's (CEM), an improved ADC, DAC, and a different control voltage distribution scheme. More sophisticated editing and tuning routines were designed, and to improve serviceability voice trimmers were reduced from 80 to 45. Some have said that Prophet 5's with the early VCO chipset (SSM) have a beefier sound, but those knowledgeable with early and later revs have said the contrary. As far as I know Dave Smith and John Bowen have never commented on this, so for the time being I'll err on the side that there is little, or no sonic difference. What is indisputable, however, is that the majority of the Rev 3 synthesizers are more operationally stable than their Rev 1 and Rev 2 counterparts.<ref name="mbll"/>

 

*Revision 3, instrument code 1000.3.0 to 1000.3.3, serial numbers from 1300. The most common. Uses [[Curtis Electromusic Specialties|Curtis]] ICs for increased stability and reliability. Is considered by some to have a thinner sound than the previous revisions. These start at serial number 1300.<ref name="vail"/><ref name="ko"/><ref name="techman"/><ref name="mbll"/><ref name="forrest"/><ref name="vse"/>

 

The Prophet's eleven oscillators - two per voice and one LFO, are based on the [[CEM 3340]] VCO IC, (before Rev 3 the [[SSM 2030]]). The IC is scaled at 1V/octave. This means that an overall CV change of 1V ideally produces a pitch change of exactly one octave. So, a CV change of 1/12V (83.3 mV) changes pitch by one semitone.<ref name="techman"/><ref name="mbll"/>

 

The voltage controlled amplifiers are based on the [[CA3280]] transconductance op-amp IC (before Rev 3 the [[SSM 2020]]).<ref name="techman"/>

 

 

== Modifications ==