Prophet VS

The Prophet VS was a hybrid 8-voice synthesizer manufactured by Sequential Circuits and released in 1986. It is notable for being the first synthesizer to use vector synthesis to structure its sound, using a joystick arranged in a "diamond" pattern for oscillator mixing.^[1][2][3] It's distinctive sound comes from mixing four 12-bit digital single-cycle waves per voice, which are then fed into analog CEM3379/3389 signal processors for filtering & amplification.^[1]

Prophet VS
Sequential Circuits Prophet VS
Manufacturer	Sequential Circuits
Dates	1986-87
Technical specifications
Polyphony	8
Timbrality	2-part
Oscillator	12-bit digital 4 per voice 96 preset & 32 user waveforms
LFO	2
Synthesis type	Vector Sample & Synthesis (S&S)
Filter	Analog low-pass filter
Attenuator	5-stage loopable envelope generator
Aftertouch expression	Yes
Velocity expression	Yes
Storage memory	Internal: 100 patches + 32 user waves Cartridge: 100 patches + 32 user waves
Effects	Stereo Chorus Voice Panning
Input/output
Keyboard	61-key 0 (rack version)
Left-hand control	Pitch, Modulation
External control	MIDI

Features and architecture

Sound generation

The VS has 8 voices, each one featuring up to four digital oscillators. Each oscillator is chosen from a table of 0-126 12-bit single cycle waveforms, with the 127th selection being a noise generator.^[1][4]

Waves 32-126 are programmed into the firmware EPROMs and can't be externally modified. However, waves 0-31 are the user wave space and can be overwritten with custom samples utilizing the MIDI sample dump standard.^[1] Another unique characteristic of the VS is that the user waves can be manually edited with the onboard wave editor, mixing up to 4 waves into a single one or adjusting individual harmonics similarly to additive synthesis.^[4]

Each voice has a CEM3379/3389 analog signal processor which gives voltage control over the filter, amplifier, and panning. Modulation of panning CV utilizing the modulation matrix can create lush moving stereo patterns.^[1][4]

Hardware

The VS uses an 8MHz Motorola 68000 as the main processor, along with two 27256 EPROMs for the operating firmware. Besides the usual 7400 & 4000 series logic chips, there are several unique or hard-to-find parts^[5]

• I-625 Voice Chip^[6] x4 - Each unit uses these for Waves A-D. 8 digital oscillators plus noise generator. These are unique to the VS.
• 68B01 Keyboard Controller - Scans the mechanical keyboard and calculates velocity values. Also used in the Prophet 2000.
• CEM5510 x4 - 8-channel high-speed sample and hold. Used to fake VCAs for oscillator mixing. These are unique to the VS.
• CEM5530^[7] x2 - 30-channel sample and hold. Used to fake VCAs for voice mixing.^[8] This is a common point of failure, and several aftermarket replacements are available. Also used in the Studio 440 and Keytek CTS-2000.
• CEM3365^[9] x2 - Dual DAC multiplier.
• CEM3379^[10] or CEM3389 x8 - Analog VCF, VCA, and voltage-controlled panning.

Legacy

After Sequential was acquired and shut down by Yamaha in 1989, Dave Smith and a handful of the development team moved to Korg, where they worked on developing the Korg Wavestation.^[1][11] Yamaha then expanded upon the VS technology to create the Yamaha SY22 and SY35 in 1990, adding FM synthesis.^[12]

In the 2020s, Behringer released two clones of the Prophet VS, a eurorack synth engine called the "Victor" and a miniature version of the complete synth called the "Pro VS Mini".^[13][14]

While modernizing the appearance of the joystick for all following vector based instruments, functionally the "diamond" layout has been followed ever since.^[8]

Notable users

• John Carpenter^[12][15]
• Prince^[16]
• Trent Reznor^[12][17][18]
• Rush^[19] - The VS Choir is featured prominently on the album Hold Your Fire.