The AX80 is a polyphonic analogue keyboard synthesizer manufactured by Akai Professional in 1984. It was Akai's first venture into the professional electronic musical instrument market. The AX80 used digitally controlled oscillators (DCO) and filter circuitry based on the Curtis Electronics CEM 3372 integrated circuit. It was marketed as part of a line of project studio equipment called the Akai Music Studio System, which included the S612 digital sampler the MR16 drum machine, the MS08 sequencer, and the MG1212 multitrack tape recorder, at a price of $1,695 US.
Features and cabinet
This electronic keyboard is an 8-voice polyphonic, digitally controlled analogue synthesizer. It has 64 memory locations for sounds ("patches"), arranged in two banks of 32 each, plus a bank of 32 factory preset sounds. The instrument has basic MIDI implementation, but lacks the ability to save or restore sounds except by using cassette tape.
Front panel
The front panel has a volume knob, a master tuning knob, a data entry knob for programming patches, modulation and pitch wheels with knobs for the depth of the effect, and various buttons to switch on and off modulation destinations, enable chord memory, transpose the keyboard, or infinitely sustain notes. The case is black metal with fluorescent displays to indicate the status of different synthesis parameters (see Figure 1), and black rubberized end pieces. Other version, possible earlier may have gloss painted wood ends.
Back panel
The back panel is unusual in that it is tilted from vertical so that the connectors can be seen from the front of the instrument. There are quarter-inch jacks for recording data to cassette tape, sustain and program change footpedal jacks, MIDI in, out and "thru" DIN connectors, a monaural quarter-inch audio output, a quarter-inch headphone jack, and memory protect and power switches. Some models have a voltage selection for the power supply on the underneath of the synth.
Keyboard
The keyboard is five octaves (61 notes, C to C) and is unweighted. It has velocity, but not aftertouch, sensitivity. The output MIDI velocity values span the full range (up to 127), but only discrete "steps" are used (in other words, not every integer value from 1 to 127). It uses rubber keypad type membrane switches, rather than J-wires. A common issue can be keys not working. This can be due to contamination under these pads.
Voice architecture and sound programming
Voice architecture
The synthesizer voices are somewhat similar to those found in the Roland JX-3P or Teisco SX-240, in that there are two oscillators (referred to as "OSC"s) per voice, with the option of sawtooth and/or square waveforms. These oscillators are controlled digitally with analog circuitry used only to create the sawtooth waveshape. OSC2 can be synchronized to OSC1, or the two oscillators can be cross-modulated. The OSCs can be separated by semitone intervals (up to four octaves) and detuned (to approximately a semitone). There is pulse-width modulation of the square wave of OSC1 (with a dedicated low-frequency oscillator (LFO) for this) and a square-wave sub-oscillator that is fixed at one octave lower. OSC2's pitch can be modulated by one of the two ADSR envelope generators, which are dedicated to VCA volume and VCF cutoff frequency. The filter is a 24dB/octave (four-pole) resonant lowpass type, and there is also a separate 12 dB/octave highpass filter that is not envelope controlled.
Tracking of filter cutoff frequency with keyboard position is fully variable, allowing for sounds to become either "brighter" or "darker" as higher notes are played. Keyboard velocity can affect volume and/or filter cutoff.
The modulation section of this synthesizer features four low-frequency oscillators. Three of these each have four available waveforms (sine, square, sawtooth and ramp), and these LFOs are dedicated to filter cutoff, and pitch of each of the two oscillators. These also have a programmable delay before their effect sets in. The fourth LFO is dedicated to pulse-width modulation of OSC1, and only its rate and depth are programmable.
There is also a programmable output level for each patch, to help balance loud and soft sounds. Notably missing from the voice architecture are white noise and portamento.