Aphex Aural Exciter Type B Used Vintage

This is from a smoke free studio and original owner in great shape. It's from the 80s.

In 1975 the Aphex Aural Exciter was unleashed upon an unsuspecting studio, broadcast and film industry. Most engineers and producers found that the device gave increased presence, clarity, and a greater perception of 'loudness' without increasing level. Later Aphex Systems introduced their Type B low-cost version of the original Exciter for the masses.

What It Does

The Aphex works on the principle of generating, within its circuits, fourth and fifth harmonics of the input signal which are mixed in with the input signal at the output. It is thought by the psycho-acoustic researchers that these harmonics are the minute cues which our subconscious minds interpret as 'presence' or 'realness'. It is claimed that it is these missing cues that the Aphex Aural Exciter re-creates and adds back to the main signal to change the way in which we perceive what we hear. Other conventional types of processors such as equalisers or reverberation, enhance those parts of the signal that are left when these cues are masked by the recording process. The Aphex Aural Exciter replaces these masked sounds.

Because the harmonics generated are derived from the main signal, they are musically related. The harmonic structure of each sound or instrument, therefore, is strengthened, allowing it to stand out from others. This manifests itself in a perceived increase in clarity or treble boost without giving any measurable increase in level.
 

How It Does It

The main signal going into the Aphex Aural Exciter passes through unchanged. All the processing is done in an outside loop (called a side-chain) and this processed signal is added in very small amounts to the main signal. See Figure 1.
 

Before the signal in the side-chain reaches the harmonic generator, it goes through a tuneable high-pass filter which removes any unwanted low frequency information. The level of this signal is then metered by a multi-coloured LED before it goes to the harmonic generator. The generated harmonics are then added in with the original signal, and the mix varied by the Mix control.

Aphex Aural Exciter Type B

The Aphex Aural Exciter Type B is a 2-channel stereo device which, of course, can be used as two monos. It comes in its 19" rack-mounted form and is 1U high. At the rear of the unit are ¼" jack sockets for input and output signals of both left and right sides. There is also a switch for adjusting the operating level of the unit to match equipment being run at +4 dBV or -10 dBV, the operating level which is appropriate to most home recording equipment. (More of this later.) Both input channels are of high impedance (47k Ohms) and the outputs are of low impedance (150 Ohms). This means that there should be no difficulty interfacing the Aphex with other equipment. The instructions supplied with the unit give a comprehensive guide to various ways of patching the device. It is designed to operate at line levels and, therefore, there is no input suitable for microphone level.

Controls

The controls of the unit are very simple to understand and operate. On the left is the Drive Control which adjusts the amount of gain into the unit. Next to this there is a flashing tri-colour LED which will show mostly green/yellow with occasional flashes of red on peaks. This would indicate a good input level; if the light was consistently green, this would indicate insufficient level into the unit; too much red would indicate overload and possible distortion.

The next control (called Tune) is the adjustment for the hi-pass filter which, as we have said, will roll off any unwanted low frequency information going to the harmonics generator. The tuning of the filter will alter the amount of input level and this will show on the LED. Therefore, it must be used in conjunction with the Drive Control.

The Mix Control adjusts the amount of effect being mixed in with the input signal. As the manufacturers point out and as we found by experimentation, it is easy initially to mix in too much of the device but the in/out switch allows one to make an instant A/B comparison of input and output (original and treated signals).

The Aphex Aural Exciter Model B is a very well constructed, simple to use device which has many interesting applications and areas to explore in studio, cassette duplication room and in sound reinforcement operations. The manufacturers had made the device easily compatible with -10dBV operation which is the level of operating that most people in home recording will be using. At the same time, it is easily switch-able for use at the professional level of +4dBV. There are those, of course, whose mixers have been adjusted for the lower level of operating, who have -10dBV for a reading of 0VU at their group outputs but still have +4 dBV across their insert points.