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[[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>
[[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>


== Overview ==
== Features ==
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 4-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 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">[https://web.archive.org/web/20060910020427/http://users.adelphia.net/~cygnusx_1/prophet5.html Prophet 5 Synthesizer] by Matt Bassett</ref>


Both oscillators can generate [[sawtooth]] wave and [[square]] waves (with variable pulse width). Osc B can also generate a [[triangle wave|triangle]] wave and be detuned over a [[semitone]]. The oscillators can be played in sync, or in poly-mod (polyphonic modulation), where osc B and the filter EG modulates the frequency or pulse width of osc A, or the filter cutoff frequency.<ref name="oman"/><ref name="vail"/><ref name="ko"/><ref name="mbll"/><ref name="forrest"/>
Both oscillators can generate [[sawtooth]] wave and [[square]] waves (with variable pulse width). Osc B can also generate a [[triangle wave|triangle]] wave and be detuned over a [[semitone]]. The oscillators can be played in sync, or in poly-mod (polyphonic modulation), where osc B and the filter EG modulates the frequency or pulse width of osc A, or the filter cutoff frequency.<ref name="oman" /><ref name="vail" /><ref name="ko" /><ref name="mbll" /><ref name="forrest" />


Controlled by the mod-wheel the LFO (with square, saw or triangle wave options) can be mixed with pink noise to modulate the frequency or pulse width of the oscillators or the filter cutoff frequency. The Prophet-5 uses a 4-pole resonant [[low-pass filter]]. The filter has a dedicated ADSR envelope and keyboard tracking.<ref name="oman"/><ref name="ko"/><ref name="mbll"/><ref name="vse">[http://www.vintagesynth.com/sci/p5.php Sequential Circuits Prophet 5], Vintage Synth Explorer</ref>
There is also the option to retune each of the twelve notes in the octave, to allow for [[alternative tuning]]s.<ref name="mag">''[http://www.synthmuseum.com/magazine/0011bc.html Sequential Circuits Prophet-5]'' by Brad Coates, Australian Musician Magazine, 1998.</ref>


Controlled by the mod-wheel the LFO (with square, saw or triangle wave options) can be mixed with pink noise to modulate the frequency or pulse width of the oscillators or the filter cutoff frequency. The Prophet-5 uses a 4-pole resonant [[low-pass filter]]. The filter has a dedicated ADSR envelope and keyboard tracking.<ref name="oman" /><ref name="ko" /><ref name="mbll" /><ref name="vse">[http://www.vintagesynth.com/sci/p5.php Sequential Circuits Prophet 5], Vintage Synth Explorer</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 [[CPU]] keeps the VCOs in tune, generates most [[CV/Gate|CV]]s from [[patch memory]] or panel knobs and switches, and assigns the voices to the keys being played.<ref name="techman"/><ref name="mbll"/>
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 was the first synthesizer to feature five fully polyphonic voices and to be able to store and recall every patch parameter for up to 40 memories, (later expanded to 120).<ref name="mag" /><ref name="reid">''[https://web.archive.org/web/20150510024530/http://www.soundonsound.com/sos/mar99/articles/retroprophet.htm Sequential Circuits – Prophet Synthesizers 5 & 10 (Retro)]'' by Gordon Reid, Sound On Sound, March 1999</ref><ref name="dub">[http://blog.dubspot.com/prophet-5-spotlight/ Classic Gear Spotlight: Sequential Circuits Prophet-5 Synthesizer] by Ross Kelly, Dubspot, 8 Nov 2016</ref>
⚫
=== Revisions ===

⚫
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"/>
⚫
== Revisions ==
⚫
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" />


There were three ''revisions'' of the Prophet-5 between 1978 and 1984:
There were three ''revisions'' of the Prophet-5 between 1978 and 1984:
*Revision 1, , instrument code 1000.1, serial numbers 1-182. The least common. Uses [[Solid State Micro Technology For Music|SSM]] ICs. These were very unreliable. Cannot be retrofitted for [[MIDI]].<ref name="techman"/><ref name="mbll"/><ref name="forrest">''The A-Z of Analogue Synthesisers Part Two'' by Peter Forrest, Short Run Press Ltd, 1996. p. 114.</ref><ref name="reid">''[https://web.archive.org/web/20150510024530/http://www.soundonsound.com/sos/mar99/articles/retroprophet.htm Sequential Circuits – Prophet Synthesizers 5 & 10 (Retro)]'' by Gordon Reid, Sound On Sound, March 1999</ref>
* Revision 1, , instrument code 1000.1, serial numbers 1-182. The least common. Uses [[Solid State Micro Technology for Music|SSM]] ICs. These were very unreliable. Cannot be retrofitted for [[MIDI]].<ref name="techman" /><ref name="mbll" /><ref name="forrest">''The A-Z of Analogue Synthesisers Part Two'' by Peter Forrest, Short Run Press Ltd, 1996. p. 114.</ref><ref name="reid" />
*Revision 2, instrument code 1000.2, serial numbers 184 to 1299. Uses SSM ICs. Is usually considered to be the better-sounding version of the Prophet-5.<ref name="ko"/><ref name="techman"/><ref name="mbll"/><ref name="forrest"/><ref name="vse"/><ref name="reid"/>
* Revision 2, instrument code 1000.2, serial numbers 184 to 1299. Uses SSM ICs. Is usually considered to be the better-sounding version of the Prophet-5.<ref name="ko" /><ref name="techman" /><ref name="mbll" /><ref name="forrest" /><ref name="vse" /><ref name="reid" />
*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"/>
* Revision 3, instrument code 1000.3.0 to 1000.3.3, serial numbers from 1300. The most common. Uses [[OnChip Systems|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" />


=== Unusual components ===
== Significant electronics ==
[[File:Prophet 5 analog section block diagram.png|thumb|center|500px|A simplified block diagram of the Prophet 5's analog section.]]
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 Prophet's eleven oscillators – two per voice and one LFO, are based on the [[CEM3340]] VCO IC, (before Rev 3 the [[SSM2030]]). 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 Prophet's five low-pass filters are based on the [[CEM 3320]] VCF, (before Rev 3 the [[SSM 2040]]). Its scale matches the VCO scale of 1V/OCT, so it is also adjusted in semitones by 83-mV DAC steps.<ref name="techman"/><ref name="mbll"/>
The Prophet's five low-pass filters are based on the [[CEM3320]] VCF, (before Rev 3 the [[SSM2040]]). Its scale matches the VCO scale of 1V/OCT, so it is also adjusted in semitones by 83-mV DAC steps.<ref name="techman" /><ref name="mbll" />


The filter and amplifier envelope generators are based on the [[CEM 3310]], (before Rev 3 the [[SSM 2050]] EG). Its output is a positive DC voltage whose level changes over the time periods set by the input timing CV's. When applied to the VCF and the final VCA the transient voltage determines the frequency and amplitude contours of the voice.<ref name="techman"/><ref name="mbll"/>
The filter and amplifier envelope generators are based on the [[CEM3310]], (before Rev 3 the [[SSM2050]] EG). Its output is a positive DC voltage whose level changes over the time periods set by the input timing CV's. When applied to the VCF and the final VCA the transient voltage determines the frequency and amplitude contours of the voice.<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"/>
The voltage controlled amplifiers are based on the [[CA3280]] transconductance op-amp IC (before Rev 3 the [[SSM2020]]).<ref name="techman" />


The CPU is a [https://en.wikipedia.org/wiki/Zilog_Z80 Z80].<ref name="techman"/>
A [https://en.wikipedia.org/wiki/Zilog_Z80 Z80] [[CPU]] keeps the VCOs in tune, generates most [[CV/gate|CVs]] from [[patch memory]] or panel knobs and switches, and assigns the voices to the keys being played.<ref name="techman" /><ref name="mbll" />


== Modifications ==
== Modifications ==
=== MIDI ===
=== MIDI ===
Some of the Prophet 5's that were MIDI'd at the factory or the early Rev 3 retrofits were problematic in that they would lock up randomly, and more often than not, after the units had been on for a while. The reason for this was that the retrofit demanded increased current from the +5 Volt digital supply. The supply design "floats" its 7805 regulator ground via a diode, producing an output voltage of +5.6 volts to allow some headroom (a series diode on the CPU drops this back to 5 volts). In some cases, with component aging and high ambient temperatures, the supply voltage dips below acceptable levels causing the instrument to lock up. The solution to the problem is to add an additional diode to the power supply board, in series with the existing one. This can be done without disassembling the power supply: locate diode IN4002 (D505) at the center of the power supply board just behind the solder pads for the 7805 regulator. De-solder the left (anode) diode lead only and prepare a IN4002 and install on the board with the cathode (banded end) up. Complete by soldering the two diode ends together, keeping the leads no more than 3/8". <ref name="mbll"/>
Some of the Prophet 5's that were MIDI'd at the factory or the early Rev 3 retrofits were problematic in that they would lock up randomly, and more often than not, after the units had been on for a while. The reason for this was that the retrofit demanded increased current from the +5 Volt digital supply. The supply design "floats" its 7805 regulator ground via a diode, producing an output voltage of +5.6 volts to allow some headroom (a series diode on the CPU drops this back to 5 volts). In some cases, with component aging and high ambient temperatures, the supply voltage dips below acceptable levels causing the instrument to lock up. The solution to the problem is to add an additional diode to the power supply board, in series with the existing one. This can be done without disassembling the power supply: locate diode IN4002 (D505) at the center of the power supply board just behind the solder pads for the 7805 regulator. De-solder the left (anode) diode lead only and prepare a IN4002 and install on the board with the cathode (banded end) up. Complete by soldering the two diode ends together, keeping the leads no more than 3/8".<ref name="mbll" />

This procedure isn't a cure-all for Prophet 5 lock-ups as less common causes are power supply, CPU malfunction, battery backup, clock and reset circuits.<ref name="mbll"/>
This procedure isn't a cure-all for Prophet 5 lock-ups as less common causes are power supply, CPU malfunction, battery backup, clock and reset circuits.<ref name="mbll" />


=== Other ===
=== Other ===
Section 11 of the technical manual for Rev 3 describes converting Rev 3.0 or 3.1 Prophets to Rev 3.2.<ref name="techman"/>
Section 11 of the technical manual for Rev 3 describes converting Rev 3.0 or 3.1 Prophets to Rev 3.2.<ref name="techman" />


Section 13 of the technical manual for Rev 3 describes a modification to increase the patch memory from 40 to 120.<ref name="techman"/>
Section 13 of the technical manual for Rev 3 describes a modification to increase the patch memory from 40 to 120.<ref name="techman" />


== Prophet-5 like synth modules ==
== Prophet-5 like synth modules ==
* AMSynths AM8320 Prophet Filter
* AMSynths AM8320 Prophet Filter
* Dave Smith Instruments - DSM01 Curtis Filter
* Dave Smith Instruments – DSM01 Curtis Filter
* Division 6 Filtare SEIII
* Division 6 Filtare SEIII
* Doepfer A-122 24dB Lowpass (CEM)
* Doepfer A-122 24dB Lowpass (CEM)
* Synthesis Technology E440 Discrete OTA VCF
* Synthesis Technology E440 Discrete OTA VCF
* Tiptop Audio Z2040 Prophet-5 Filter
* Tiptop Audio Z2040 Prophet-5 Filter


== See also ==
== See also ==
* [[Sequential Circuits Pro One]], monophonic analog synth with similar circuitry to the Prophet-5
* [[Sequential Circuits Pro One]], monophonic analog synth with similar circuitry to the Prophet-5
* [[Sequential Circuits Prophet 600]]


{{iwWikipedia}}{{iwEMWiki}}{{iwSequencer}}{{iwSynthwiki}}
== References ==
== References ==
{{reflist}}
{{reflist}}


== Further reading ==
== Further reading ==
* ''The Prophet from Silicon Valley: The Complete Story of Sequential Circuits'' by David Abernethy, CreateSpace Independent Publishing Platform, 2015, ISBN 1512198323
* ''The Prophet from Silicon Valley: The Complete Story of Sequential Circuits'' by David Abernethy, CreateSpace Independent Publishing Platform, 2015, ISBN 1-5121-9832-3


== External links ==
== External links ==
* [https://www.davesmithinstruments.com/ Dave Smith Instruments]
* [https://www.davesmithinstruments.com/ Dave Smith Instruments]
* [http://www.siliconbreakdown.com/prophet5.html Sequential Circuits Prophet 5 Synthesizer], photos
* [http://www.siliconbreakdown.com/prophet5.html Sequential Circuits Prophet 5 Synthesizer], photos
* [http://users.telenet.be/prophet-5/main.htm Sequential Circuits Prophet 5 Tribute Site]
* [https://web.archive.org/web/20161008052906/http://users.telenet.be/prophet-5/main.htm Sequential Circuits Prophet 5 Tribute Site]
* Scroll down for [http://www.synthmuseum.com/sequ/seqpro501.html Comparing the Rev2 to the Rev3] by David Bellamy
* ''[http://www.synthmuseum.com/magazine/0011bc.html Sequential Circuits Prophet-5]'' by Brad Coates (www.melmusic.com.au)
* Scroll down for [http://www.synthmuseum.com/sequ/seqpro501.html Comparing the Rev2 to the Rev3] by David Bellamy
* ''[http://greatsynthesizers.com/en/test/sequential-circuits-prophet-5-milestone-and-musical-legend/ Sequential Circuits Prophet-5 – Milestone and Musical Legend]'' by Theo Bloderer 2 July 2016
* ''[http://greatsynthesizers.com/en/test/sequential-circuits-prophet-5-milestone-and-musical-legend/ Sequential Circuits Prophet-5 – Milestone and Musical Legend]'' by Theo Bloderer 2 July 2016
* ''[https://youtu.be/Ruh0B5QKBMs The History of the Prophet Synthesizer]'' by Alex Ball, YouTube, Oct 2018
* ''[https://imgur.com/a/SDcaqU3 The guts and glory of a Sequential Circuits Prophet-5 Rev 2]'' by Synthead
=== Other wikis ===
* [https://en.wikipedia.org/wiki/Sequential_Circuits_Prophet-5 Sequential Circuits Prophet-5], Wikipedia
* [http://electronicmusic.wikia.com/wiki/Prophet-5 Prophet-5], Electronic Music wiki
* [https://www.synthwiki.nl/wiki/Sequential_Circuits_Prophet-5 Sequential Circuits Prophet-5], Synthwiki.nl
=== Manuals & schematics ===
=== Manuals & schematics ===
* [http://www.synfo.nl/ Synfo.nl], rev.1 service manual, rev. 2 & 3 technical manuals
* [http://www.synfo.nl/ Synfo.nl], rev.1 service manual, rev. 2 & 3 technical manuals
Line 72: Line 82:
* [https://archive.org/details/synthmanuals-sequential Archive.org], Rev 3.3 owners & rev. 3.0/3.1/3.2 technical manual
* [https://archive.org/details/synthmanuals-sequential Archive.org], Rev 3.3 owners & rev. 3.0/3.1/3.2 technical manual
=== Mods ===
=== Mods ===
* [http://web.archive.org/web/20061231234110/http://users.adelphia.net/~cygnusx_1/prophet5_mod.html Modification for the rev.3] by Juergen Haible
* [https://web.archive.org/web/20061231234110/http://users.adelphia.net/~cygnusx_1/prophet5_mod.html Modification for the rev.3] by Juergen Haible
* Kenton [http://www.kentonuk.com/ MIDI Retrofit Kit]s for Prophet 5 Rev 2 and 3.x
* Kenton [http://www.kentonuk.com/ MIDI Retrofit Kit]s for Prophet 5 Rev 2 and 3.x
* [http://electricdruid.net/wp-content/uploads/2015/07/NoiseGen1Datasheet.pdf Electric Druid Noise Generator], replacement noise generator for Sequential Circuits Prophet-5
* [http://electricdruid.net/wp-content/uploads/2015/07/NoiseGen1Datasheet.pdf Electric Druid Noise Generator], replacement noise generator for Sequential Circuits Prophet-5
* [http://sounddoctorin.com/synthtec/sci/p5.htm Prophet 5 Technical assistance] by Bob Weigel
* [http://sounddoctorin.com/synthtec/sci/p5.htm Prophet 5 Technical assistance] by Bob Weigel
* [http://www.xero.cc/p5cass/ Index of /p5cass]


[[Category:Analog synthesizers]]
[[Category:Analog synthesizers]]

Latest revision as of 18:15, 15 February 2023

Sequential Circuits Prophet-5 Rev 3.3

The Sequential Circuits Prophet-5 released in 1978, was the first completely programmable polyphonic analog synthesizer. Dave Smith designed the electronics and coded the firmware.[1][2][3][4]

Features

The Prophet-5 is five voice subtractive synthesizer. Each voice is an individual synthesizer with two VCOs (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 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.[5][6]

Both oscillators can generate sawtooth wave and square waves (with variable pulse width). Osc B can also generate a triangle wave and be detuned over a semitone. The oscillators can be played in sync, or in poly-mod (polyphonic modulation), where osc B and the filter EG modulates the frequency or pulse width of osc A, or the filter cutoff frequency.[1][2][3][6][7]

There is also the option to retune each of the twelve notes in the octave, to allow for alternative tunings.[8]

Controlled by the mod-wheel the LFO (with square, saw or triangle wave options) can be mixed with pink noise to modulate the frequency or pulse width of the oscillators or the filter cutoff frequency. The Prophet-5 uses a 4-pole resonant low-pass filter. The filter has a dedicated ADSR envelope and keyboard tracking.[1][3][6][9]

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.[5][6]

The Prophet-5 was the first synthesizer to feature five fully polyphonic voices and to be able to store and recall every patch parameter for up to 40 memories, (later expanded to 120).[8][10][11]

Revisions

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.[6]

There were three revisions of the Prophet-5 between 1978 and 1984:

  • Revision 1, , instrument code 1000.1, serial numbers 1-182. The least common. Uses SSM ICs. These were very unreliable. Cannot be retrofitted for MIDI.[5][6][7][10]
  • Revision 2, instrument code 1000.2, serial numbers 184 to 1299. Uses SSM ICs. Is usually considered to be the better-sounding version of the Prophet-5.[3][5][6][7][9][10]
  • Revision 3, instrument code 1000.3.0 to 1000.3.3, serial numbers from 1300. The most common. Uses 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.[2][3][5][6][7][9]

Significant electronics

A simplified block diagram of the Prophet 5's analog section.

The Prophet's eleven oscillators – two per voice and one LFO, are based on the CEM3340 VCO IC, (before Rev 3 the SSM2030). 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.[5][6]

The Prophet's five low-pass filters are based on the CEM3320 VCF, (before Rev 3 the SSM2040). Its scale matches the VCO scale of 1V/OCT, so it is also adjusted in semitones by 83-mV DAC steps.[5][6]

The filter and amplifier envelope generators are based on the CEM3310, (before Rev 3 the SSM2050 EG). Its output is a positive DC voltage whose level changes over the time periods set by the input timing CV's. When applied to the VCF and the final VCA the transient voltage determines the frequency and amplitude contours of the voice.[5][6]

The voltage controlled amplifiers are based on the CA3280 transconductance op-amp IC (before Rev 3 the SSM2020).[5]

A Z80 CPU keeps the VCOs in tune, generates most CVs from patch memory or panel knobs and switches, and assigns the voices to the keys being played.[5][6]

Modifications

MIDI

Some of the Prophet 5's that were MIDI'd at the factory or the early Rev 3 retrofits were problematic in that they would lock up randomly, and more often than not, after the units had been on for a while. The reason for this was that the retrofit demanded increased current from the +5 Volt digital supply. The supply design "floats" its 7805 regulator ground via a diode, producing an output voltage of +5.6 volts to allow some headroom (a series diode on the CPU drops this back to 5 volts). In some cases, with component aging and high ambient temperatures, the supply voltage dips below acceptable levels causing the instrument to lock up. The solution to the problem is to add an additional diode to the power supply board, in series with the existing one. This can be done without disassembling the power supply: locate diode IN4002 (D505) at the center of the power supply board just behind the solder pads for the 7805 regulator. De-solder the left (anode) diode lead only and prepare a IN4002 and install on the board with the cathode (banded end) up. Complete by soldering the two diode ends together, keeping the leads no more than 3/8".[6]

This procedure isn't a cure-all for Prophet 5 lock-ups as less common causes are power supply, CPU malfunction, battery backup, clock and reset circuits.[6]

Other

Section 11 of the technical manual for Rev 3 describes converting Rev 3.0 or 3.1 Prophets to Rev 3.2.[5]

Section 13 of the technical manual for Rev 3 describes a modification to increase the patch memory from 40 to 120.[5]

Prophet-5 like synth modules

  • AMSynths AM8320 Prophet Filter
  • Dave Smith Instruments – DSM01 Curtis Filter
  • Division 6 Filtare SEIII
  • Doepfer A-122 24dB Lowpass (CEM)
  • Synthesis Technology E440 Discrete OTA VCF
  • Tiptop Audio Z2040 Prophet-5 Filter

See also

References

  1. ^ a b c Prophet-5 Synthesizer Operation Manual by Stanley Jungleib, Synthfool.com
  2. ^ a b c Vintage Synthesizers by Mark Vail, Miller Freeman, 1993, ISBN 0-87930-603-3, pp. 173-177
  3. ^ a b c d e Keyfax Omnibus by Julian Colbeck, MixBooks, 1996, ISBN 0-918371-08-2, pp. 122-124
  4. ^ About, Dave Smith Instruments
  5. ^ a b c d e f g h i j k l Sequential Circuits Prophet 5 Technical Manual by Stanley Jungleib, Synthfool.com, s. 2.2
  6. ^ a b c d e f g h i j k l m n Prophet 5 Synthesizer by Matt Bassett
  7. ^ a b c d The A-Z of Analogue Synthesisers Part Two by Peter Forrest, Short Run Press Ltd, 1996. p. 114.
  8. ^ a b Sequential Circuits Prophet-5 by Brad Coates, Australian Musician Magazine, 1998.
  9. ^ a b c Sequential Circuits Prophet 5, Vintage Synth Explorer
  10. ^ a b c Sequential Circuits – Prophet Synthesizers 5 & 10 (Retro) by Gordon Reid, Sound On Sound, March 1999
  11. ^ Classic Gear Spotlight: Sequential Circuits Prophet-5 Synthesizer by Ross Kelly, Dubspot, 8 Nov 2016

Further reading

  • The Prophet from Silicon Valley: The Complete Story of Sequential Circuits by David Abernethy, CreateSpace Independent Publishing Platform, 2015, ISBN 1-5121-9832-3

External links

Other wikis

Manuals & schematics

  • Synfo.nl, rev.1 service manual, rev. 2 & 3 technical manuals
  • Synthfool.com, Rev 3.3 owners & rev. 3.0/3.1/3.2 technical manual
  • Fdiskc.com, technical manual rev. 2
  • Archive.org, Rev 3.3 owners & rev. 3.0/3.1/3.2 technical manual

Mods

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