Prophet Pro-One

Sequential Circuits Prophet Pro-One

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Sequential circuits released amongst the first truly polyphonic synthesisers

where a group of voice circuits (5 to 10 of them) were linked to an onboard

computer that gave the same parameters to each voice and drove the notes to

each voice from the keyboard. The costs were nothing short of exhorbitant and

this lead to Sequential releasing a model with just one voice board as a mono-

phonic equivalent. The sales ran up to 10,000 units, a measure of its success

and it continues to be recognised alongside the Mini Moog as a fat bass synth.

The design of the Prophet synthesisers follows that of the Mini Moog. It has

three oscillators one of them as a dedicated LFO. The second audio oscillator

can also function as a second LFO, and can cross modulate oscillator A for FM

type effects. The audible oscillators have fixed waveforms with pulse width

modulation of the square wave. These are then mixed and sent to the filter with

two envelopes, for the filter and amplifier.

The Pro-1 had a nice bussing matrix where 3 different sources, LFO, Filter Env

and Oscillator-B could be mixed in varying amounts to two different modulation

busses and each bus could then be chosen as inputs to modulation destinations.

One bus was a direct bus from the mixed parameters, the second bus was under

the modwheel to give configurable expressive control.

LFO:

Frequency: 0.1 to 50 Hz

Shape: Ramp/Triangle/Square. All can be selected, none selected should

give a sine wave

Modulations:

Source:

Filter Env amount to Direct or Wheel Mod busses

Oscillator-B amount to Direct or Wheel Mod busses

LFO to Direct amount or Wheel Mod busses

Dest:

Oscillator-A frequency from Direct or Wheel Mod busses

Oscillator-A PWM from Direct or Wheel Mod busses

Oscillator-B frequency from Direct or Wheel Mod busses

Oscillator-B PWM from Direct or Wheel Mod busses

Filter Cutoff from Direct or Wheel Mod busses

Osc-A:

Tune: +/-7 semitones

Freq: 16' to 2' in octave steps

Shape: Ramp or Square

Pulse Width: only when Square is active.

Sync: synchronise to Osc-B

Osc-B:

Tune: +/-7 semitones

Freq: 16' to 2' in octave steps

Fine: +/- 7 semitones

Shape: Ramp/Triangle/Square

Pulse Width: only when Square is active.

LFO: Lowers frequency by 'several' octaves.

KBD: enable/disable keyboard tracking.

Mixer:

Gain for Osc-A, Osc-B, Noise

Filter:

Cutoff: cuttof frequency

Res: Resonance/Q/Emphasis

Env: amount of modulation affecting to cutoff.

KBD: amount of keyboard trackingn to cutoff

Envelopes: One each for PolyMod (filter) and amplifier.

Attack

Decay

Sustain

Release

Sequencer:

On/Off

Record Play

Rate configured from LFO

Arpeggiator:

Up/Off/UpDown

Rate configured from LFO

Glide:

Amount of portamento

Auto/Normal - first key will/not glide.

Global:

Master Tune

Master Volume

Memories are loaded by selecting the 'Bank' button and typing in a two digit

bank number followed by load. Once the bank has been selected then 8 memories

from the bank can be loaded by pressing another memory select and pressing

load. The display will show free memories (FRE) or programmed (PRG).

There is an additional Up/Down which scan for the next program and a 'Find'

key which will scan up to the next unused memory location.

The original supported two sequences, Seq1 and Seq2, but these have not been

implemented. Instead the emulator will save a sequence with each memory location

which is a bit more flexible if not totally in the spirit of the original.

The Envelope amount for the filter is actually 'Mod Amount'. To get the filter

envelope to drive the filter it must be routed to the filter via a mod bus. This

may differ from the original.

Arpeggiator range is two octaves.

The Mode options may not be correctly implemented due to the differences in

the original being monophonic and the emulator being polyphonic. The Retrig is

actually 'rezero' since we have separate voices. Drone is a Sustain key that

emulates a sustain pedal.

Osc-B cannot modulate itself in polyphonic mode (well, it could, it's just that

it has not been coded that way).

The filter envelope is configured to ignore velocity.

The default filters are quite expensive. The -lwf option will select the less

computationally expensive lightweight Chamberlain filters which have a colder

response but require zonks fewer CPU cycles.