The AX73 was a simple analogue synthesiser based around the Curtis CEM 3394 chips that were used in several Sequential Circuits synthesisers at the time. These chips offered a single voltage controlled oscillator (VCO), a voltage controlled, resonant 24db/octave lowpass filter (VCF) and a voltage controlled amplifier (VCA) and six of these were employed to create the 6-voice AX73. Because all the circuitry used true voltage controlled circuitry, this gave a warmer sound that the digital synths (or the digitally controlled analogue synths) of the time.

The AX73 also had some unique features such as totally variable 'pulse width' on all waveforms (sawtooth, square and triangle) not just the square wave. It also allowed cross-modulation of the filter by the audio oscillator for a variety of dangerous ring-modulator sounds. It also featured various dual, split and unison play modes and a simple (but slightly noisy) analogue chorus unit to fatten the sound up even further.

A 73-note velocity sensitive keyboard was chosen in preference to the 5-octave unresponsive keyboards used by most analogue synths of the time making the AX73 a very competent master keyboard.

Off the back of the AX73 came the 2U rack-mounting VX90 analogue synth module.

The voice circuitry was identical in every respect but the convenient rack mount format gave users a versatile analogue sound source in a compact, portable case.

The VX90 enjoyed a good deal of success in its time and still continues to be a favourite module in keyboard rigs as a source of useful, genuine analogue synth sounds.

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However, aware of the fact that the parameter access style of editing on both the AX73 and VX90 was less than ideal, we released the AX60 in 1985.

Internally, the AX60 had the same voice architecture as the AX73 and VX90 but had the advantage of dedicated sliders for every function.

The AX90 also added an arpeggiator with external sync options.

The AX60 was only released in the US and, until recently, has had the (dubious) honour of being the last ever truly analogue synth with a panel full of dedicated controls!

Common to all models in the range, however, was a proprietary 13-pin DIN socket that allowed you to connect an S900 for processing through the synths' analogue filters. How many people used this facility is unknown however!

Many consider this range of synths to be very underrated - indeed, these synths can produce some classic and brutal analogue synth sounds - but this can work very much to the advantage of anyone looking for a true analogue synth on a budget as they are often very inexpensive to buy today.

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