Sequential Circuits Prophet 5 SN 6252

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via this auction, also on Reverb

"Up for sale here is the most classic synthesizer from the 1980s. We have owned this Prophet 5 for about two years and was only used in the studio. It has been very well cared for and professionally maintained. With an instrument this old, you must expect some cosmetic wear though this one is very clean. There is nothing more than a few surface scratches, new knobs on the Master Tune and Volume functions, and action a little weak on the lowest F note but can still be played. Overall this keyboard is in very good condition and functions perfectly.

The Prophet-5 has been thew world’s leading polyphonic keyboard synthesizer since its appearance in January, 1978. Renowned among professionals for the range quality of its sound, it provides five-voice capability and now allows the keyboardist to install select from 120 sounds (programs). All programs can be fully customized and stored internally, or on audio tape via the built in cassette interface.

The Prophet-5 actually contains five individual synthesizers, termed “voices”. For its producible sound sources, each voice contains two voltage controlled oscillators (VCOs), referred to as OSC A and OSC B. OSC A, OSC B, and a white noise source can be mixed into a resonant low-pass voltage controlled filter (VCF). The filter modifies the voice timbre under control of its four-stage envelope generator. The filter may also serve as a sound source. Following each filter, a voltage-controlled amplifier (VCA) also controlled by a four-stage envelope generator shapes the voice amplitude. Only one voice is depicted on the control panel, because the voice controls “patch” the five voices identically. This makes the voices homophonous— they sound alike— with pitch differences corresponding to (at most) five keys simultaneously-held keys.

The term “digital-analog hybrid” is often used to described the Prophet. This means that instead of directly controlling the analog synthesizer voices, the keyboard and most controls are actually devices which input “data” to a microcomputer system which in turn “programs” the voices. The microcomputer has three main functions. First, it solves the of generating five independent sets of voice control voltages and gate signals (which operate the envelope generators) from a single keyboard. Second, its digital memory provides a way to store all of the switch and knob settings which form a program. These programs are retained by the microcomputers memory even when the Prophet is turned off, thats to a small battery with a 10-year life. Third, the microcomputer system keeps the ten voice oscillators in tune."