6-voice 6-octave synthesizer, introduced by Akai in the mid-1980s.
The 73-note keyboard is velocity-sensitive. The pitch bend wheel, located next to the modulation wheel, is programmable to control cutoff. A 13-pin DIN input jack allows connection to a sampler up to an Akai S950.
All the circuitry, based on a Curtis CEM 3394 chip, is analogue, but the interface is digital. Settings are controlled via a 22-key keypad and a data slider and supervised on a 15-character backlit LCD. The AX73 supports a maximum of 100 patches.
The audio path consists of a single VCO, VCF, two ADSR envelopes, an LFO with five waveforms including sample & hold), a dynamic VCA and a chorusing unit. It also has a portamento feature.
The VCO can produce four variable pulse-width waveforms (triangle, sawtooth, pulse, and combined triangle and sawtooth), noise using PWM with a separate, global LFO. The VCF consists of a 24 dB resonant four-pole lowpass in series with a non-resonant highpass filter. Curiously enough, cutoff can be VCO cross-modulated. The ADSR VCA envelope generators have selectable destinations, VCO-pitch, and VCF cutoff.
A rackmounted module very similar to the AX73 exists under the name VX90. (A keyboard version called AX90, intented to be a slight upgrade to AX73, was developed but never went into production.) The more well-known, bi-timbral Akai AX60 is based on the same chip and has a knob-based interface and an arpeggiator, but only one envelope generator. Within the AX series, they are all successors of the Akai AX80.
Because it is extremely underrated and unknown, also in comparison to its cousin AX60, used AX-73's can be found at bargain prices on occasion. It is an excellent synthesizer for creating the phat bass heard in most electronic music produced from the 1980s and on. It has been used by artists such as N-Trance.
The exterior of the AX-73 is a light-gray painted steel surface, making it look an awful lot like a Chinese army tank, and weighing close to as much as a small ICBM: 15 kg (33 lbs). Well, a small ICBM, okay?
Not a cut-and-paste writeup. Yours truly is a happy owner of one.