|Oscillator||2 DCOs per voice|
|Synthesis type||Analog Subtractive|
|Filter||1 low-pass per voice|
|Attenuator||1 VCA per voice
1 ADSR envelope per voice
|External control||Poly-61M has MIDI|
The KORG Poly-61 is a programmable polyphonic synthesizer released by Korg in 1982, a digitally controlled successor to the Polysix. It was notable as it was the first Korg synthesizer to feature a pushbutton user interface, dispensing from the Polysix's knobs and switches. In 1984 a MIDI version, the Poly-61M was released featuring basic MIDI implementation.
The filter has the typical controls for cutoff, resonance, keyboard tracking and envelope amount. Some of these are rather limited by the poor parameter resolution. Keyboard tracking is simply "on" or "off" for example, and resonance and envelope level (here labelled "EG Intensity") have only 8 values.
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.
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.
Differences from the Korg Polysix
Although similar in some ways, there are numerous differences between the two:
- Many parameters on the Poly-61 have limited resolution of 8 steps, whereas Polysix parameters have 256 step resolution.
- The Poly-61 has DCOs versus VCOs on the Polysix.
- The Poly-61 has two oscillators versus one on the Polysix.
- The Poly-61M has basic MIDI implementation.
- The Poly-61 has 64 memories, instead of 32 on the Polysix.
- The Polysix has an analog effects board, whereas the Poly-61 has no effects.