Korg Poly-61

The KORG Poly-61 (PS-61) is an analogue programmable polyphonic synthesizer released by Korg in 1982,[1] as a successor to the Polysix. It was notable for being Korg's first largely "knobless" synthesizer - featuring a push-button interface for programming, dispensing with the Polysix's knobs and switches. The Poly-61 also uses digitally controlled analog oscillators or DCO's (Roland's Juno-6 had made the same leap the previous year), in place of the Polysix' VCOs. The Poly-61 also boasted double the amount of patch memory (64 memory positions versus the Polysix's 32), but did not feature its predecessor's on board effects.

Poly-61
Poly-61
ManufacturerKorg (Keio Electronic Laboratories)
Dates1982-1986
Technical specifications
Polyphony6 voices
TimbralityMonotimbral
Oscillator2 DCOs per voice
LFO1/2
Synthesis typeAnalog Subtractive
Filter1 low-pass per voice
Attenuator1 VCA per voice
1 ADSR envelope per voice
Storage memory64 patches
Input/output
Keyboard61 keys
External controlPoly-61M has MIDI

In 1984 a MIDI version, the Poly-61M was released featuring basic MIDI implementation, however, prior to that, a person could order a factory installed Poly 61 with MIDI in and MIDI out jacks installed on a plate on the rear of the keyboard, simply called Poly-61 with Factory Installed MIDI. The MIDI implementation was basic with only note on and note off information, partly as the synthesiser was not touch sensitive.

Audio path

Oscillators

The Poly-61 offers two DCOs per voice. DCO1, a more traditional design, provides sawtooth, pulse, and PWM waveforms. DCO2, based on low-resolution counter ICs, has only sawtooth and square, and is not available on its own.

Filter

The filter has the typical controls for cutoff, resonance, keyboard tracking and envelope amount. Some of these are rather limited by the parameter resolution. Keyboard tracking is simply "on" or "off" for example, and resonance and envelope level (here labelled "EG Intensity") have only 8 values. However, when manipulated by internal LFOs, the resolution is considerably better without notable stepping.

Output

The final component in the audio path is a VCA. It can be driven by the envelope generator or a CV/Gate pulse.

Embedded processors

NEC D8049C - 8 bits, 11 MHz (max.), 40 pins (DIP), Supply Voltage = 5V

There are 2 of them on the CPU board (KLM-509), one is a Programmer and the other is an Assigner.

The 8049 has 2 kB of masked ROM as well as 128 bytes of RAM and 27 I/O ports. The µC's oscillator block divides the incoming clock into 15 internal phases, thus with its 11 MHz max. crystal, one gets 0.73 MIPS (of one-clock instructions). Some 70% of instructions are single byte/cycle, but 30% need two cycles and/or two bytes, so raw performance is closer to 0.5 MIPS. The minimum instruction length is 8 bits and the maximum instruction length is 16 bits.[2]

Modulation

Envelope generator

The envelope is an ADSR type. All parameters can only be set to one of 16 values.

There are 6 SSM-2056 analog envelope generator chips used in the Poly 61, each being controlled by discrete 4-bit D/A converters. This means there are only 16 possible settings for each of the ADSR parameters.

LFO

The LFO (known as a 'modulation generator' on the Poly-61) is a simple triangle wave that can be routed to the DCOs or VCF. It has a variable delay before it is triggered.

Joystick

The joystick controls a second LFO, adjustable by a knob with rate indicator LED, and entirely independent of the main LFO, although the effect can be cumulative. The joystick can be used to route this to DCO pitch (vibrato) or VCF. As control of this LFO is entirely manual, it does not feature in the programmable patch structure of the synth.

Performance features

Joystick

Unlike the separate pitch and modulation wheels of the Polysix, the Poly 61 features a full joystick, with variable pitchbend (+/- about 7 semitones), and an independent LFO (see above).

Chord memory

As well as standard 6-voice polyphony, a chord memory can be engaged, memorising any chord voicing held down while pressing the Chord Memory button. This chord is then replicated, its lowest note matching any note played on the keyboard. A hold function works in either Poly or Chord mode, with a dedicated input jack for a release foot pedal.

Arpeggiator

There is a simple arpeggiator with dedicated control buttons and tempo knob, which can work in conjunction with the chord memory for moderately sophisticated sequences.

Notable users
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References
  1. "POLY-61 Programmable Polyphonic Synthesizer (1982-11)". Korg Museum, Sound Make Up. Korg Inc.
  2. "Archived copy". Archived from the original on 2014-02-22. Retrieved 2013-10-29.CS1 maint: archived copy as title (link)
  3. Church, Terry (February 9, 2010). "Black History Month: Jesse Saunders and house music". BeatPortal. Archived from the original on April 24, 2015. Retrieved October 16, 2011.
  4. "Jesse Saunders – On And On". Discogs. Retrieved May 23, 2012.
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