Korg Poly-61

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.

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.

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

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]

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.

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.

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.

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).

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.

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.