Sequential Circuits Pro-one
model 100 (1981)

Monophonic portable synthesizer: 2 oscillator with a complex and smart analog signal patch routing. Powerful machine, a bit underrated for years, now considered as a classic analgo machine.

KEYBOARD 37 keys. Main panel features 28 knobs, 26 switch tabs and 2 wheels for pitch and modulation control.


Back panel terminal connectors:
- audio input for external signal processing
- VCO CV input with gate
- VCO CV output with gate
- VCF CV input.
- clock input
- audio signal output

VOICE subtractive synthesis generates 1 monophonic voice with 2 portamento playmodes: automatic glides in legato mode or normal glides lag mode
A Pro1 voice is composed by 2 voltage-controlled oscillators VCO + 1 white noise generator:
VCOs have slightly different structure and all their waveform shapes can be summed :

	VCO1	VCO2
Waveforms:	saw / pulse	saw / pulse / triangle
Pulse width:	0-100% duty	0-100% duty
Volume mix:	yes	yes
Tuning:	yes	yes
Octaves:	4 octaves	4 octaves + submode (lfo)
Hardsync:	1 > 2	-

 

FILTER is a 4-poles resonant lowpass filter based on chip Curtis CEM 3320.
In addition 2 extra functions:
- keyboard track process
- audio input processes external line sources.

ENVELOPE 2 EGs:
- EG1 VCA amplitude ADSR
- EG2 VCF filter ADSR
Special drone mode ovverides the VCA EG settings.

LFO a single modulator 1 to 30 Hz frequency range modulates 2 destinations:
- VCO pitch
- VCF cutoff.
The modulator's cycle can be retriggerand offers 3 summable shapes: saw, triangle and square.

MATRIX the modulation wheel section features a signal routing Matrix system:

Sources	Destinations
EG VCF	VCO 1 pitch
VCO2	VCO 2 pitch
LFO	VCO 1 rectangular width
	VCO 2 rectangular width
	VCF cutoff

 

SEQUENCER & ARPEGGIATOR a simple and intuitive 40 steps notes sequencer is onboard with a handy transpose shifter, arpeggiator is limited to up & down directions. note that RAM is volatile consequently the created sequence is not memory-retained.
SYNC sequencer and arpeggiator use LFO frequency as clock, but it is possible sync to external clock sync IN (pulses signal at +5V).

MAINTENANCE the synth is pretty reliable in time.
Classic maintenance issues are the noisy keys with J-wire version that needs new plastic bushings replacement.

RELATED FAMILY:

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VST PLUGIN / SAMPLED VERSION there are some free and commercial samples set andplugin VST :

	name	price	link	demo
	Pro one synthetic percussion	free sample pack		n/a
	EFM PRO1	FREE VST		n/a
	ZARG MUSIC	Commercial $$$ for Creamware scope system only
	Sampleism	Commercial $ samples		N/A

 

AUDIO DEMO

precint 13 (overdub) with drums bassline with Akai XR-10 resonance with Roland tr-8 Sync mode with Yamaha TX16W

harsh and lo-fi Happy fat time smooth filter autob

 

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SEQUENTIAL PRO-ONE MANUAL

SERVICE MANUAL / SCHEMATICS

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