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The Excitement Mounts (in a 19" Rack Box)

Aphex Aural Exciter Type C

Article from Home & Studio Recording, January 1986

Adventure on the high Cs.

The first in-depth review of the Aphex Aural Exciter Type C.

Since its introduction in 1975, the Aural Exciter has become world famous, but like all popular products, it was only a matter of time before the competition started to market similar devices. Some of these alternative systems are very good and I suspect that this is one of the reasons Aphex have decided to hit back with a lower cost, higher specification model. The Type C looks on the face of it very much like the Type B and is very similar in use, but there are improvements as well as the reduction in cost. Before launching into detail, it is worth taking another look at exactly what an Exciter does.

The Principles of Excitement

There is still a lot of mystery surrounding the operation of the psychoacoustic enhancer. People still say 'Yes, but what does it actually do?' Well it really isn't a very complicated device and you might be interested to know that it creates the illusion of extra clarity by introducing controlled amplitude and phase distortion. What happens is this.

The input signal is buffered via a variable gain amplifier controlled by the Drive control and then passed through a variable high-pass filter with a 12dB per octave characteristic, and this is the Tune control. The output from the Tune control is in fact that portion of the signal that is treated and harmonically enriched before being added to the output signal. This filtered signal is fed into a VCA and here some degree of compression takes place and also some amplitude-dependent distortion. This works by feeding the control pin of the VCA with a combination of the compressor side-chain signal and a portion of the VCA input.

This subtly distorted signal is then passed via the mix control back into main signal path. It sounds almost too crude to be true but the effect is remarkable.

The compressor time constants are chosen to add impact to transients and the distortion is harmonically related to the original sound in such a way that the human ear/brain perceives it as a natural part of that sound. In practice, this means that a sound lacking in upper harmonics can be brightened up in a way that could never be done using conventional EQ and the overall transparency is much improved. Due to the ear and brain's response to this extra information, only a very small amount need be added for the system to be effective so this increase in apparent loudness, brightness and clarity adds no significant level to the signal.

All this theory was true of the Aphex B so what is the difference?

B and Beyond

Though the B is a fine device, it does suffer from a limited Drive range and this means that you tread a fine line between overload distortion or insufficient Drive to produce a strong effect. Also the B didn't use the best low noise ICs that it could have done, and so improvements have been made in this area as well. To be fair, most noise is due to the programme material rather than the process but of course the Exciter enhances residual noise just as well as it enhances signal. This isn't too serious though, as the increase in noise is a lot less than you would get if you tried to use mere EQ to brighten up a signal and of course the result would be less satisfactory; after all, you can't EQ any frequencies that are not present.

What Aphex have done is to incorporate the essential VCA and its associated circuitry into a specially designed IC which has given a wider operating range to the Drive control and lower noise operation, all at a lower manufacturing cost. So much for theory... what do you get for your money?


The unit is a 1U rack mountable package with detachable ears, rather like a Spitting Image Prince Charles. The panel is the characteristic silver and blue of Aphex and the unit contains two identical channels of electronics which may be used either independently or together to process a stereo signal. Each channel has just three rotary controls, the In/Out button being common to both, and the operation is quite straightforward.

"The lower price of £299 inc VAT means that this unit can be afforded by the majority of serious home studios..."

The unit is connected either in line with the individual signal to be processed or in line with the complete stereo mix and the Drive control set such that the tri-coloured display LED flashes from green to yellow and only hits red in the loudest peaks. To control the amount of enhancement, the Mix control is employed and the Tune control is used to enable the user to home in on the frequencies that are to be enhanced. This control is set up purely by ear but as the meter LED is connected post-filter, it may be necessary to readjust the Drive once the Tune control has been optimised. When the effect is active, the LED by the In/Out switch glows red and this reverts to green in the bypass mode. According to the instructions, the Type C is optimised to -10dBm operating levels but I am informed that there are links inside the case that can be changed if the matching is incorrect.

The rear panel is different to the Type B only in that there is the option of jack or phono connectors for both inputs and outputs and these are wired for unbalanced operation.


Enhancers in general are suitable for both corrective and creative processing and in the field of cassette duplication, a touch of excitement will result in brighter cleaner copies. Vocals can be given an intimate sparkle at either the recording or mixing stage and even the most hopelessly dull drum tracks can be revitalised and all those missing cymbals just reappear as if by magic. Acoustic guitars positively jump out of the speakers at you and soggy analogue synth sounds take on new depth. It might sound too good to be true but enhancement really works and the more humble your recording system, the more likely you are to need it.

It doesn't just end at music production as you can use enhancement on PA systems for sound reinforcement or for paging systems to improve vocal articulation. Even political speeches have been souped up by Aphex!

In Use

No matter what type of enhancer you use, the rules are the same and the trap to avoid is the temptation to use too much. The best way to do this is to switch the effect in and out at regular intervals, otherwise you will end up with a mix that is about as comfortable as a vindaloo enema. In all honesty the Type C is very much like the B but it isn't so fussy about drive levels. You still have to get the drive level about right for the best results, however.

The circuit noise is quoted as being -90dBv which is almost certainly correct but as pointed out earlier, that doesn't help if you have noisy source material as this will get even noisier when excited (rather like the staff at H&SR —Ed).

One area in which the model gave cause for concern was its tendency to emphasise sibilance on vocals. I was trying the system out on a complete mix which included a female lead vocal line and, though the majority of the track improved in transparency, the vocal sound became noticeably sibilant, even though there was no trace of such a problem before processing. This is a problem that I've not previously encountered when using either the Aphex B or any of the other popular enhancers on the market, but without lining them all up side by side and testing them with the same piece of music, it's difficult to offer more than a subjective impression at this point. So, your best bet as always is to try before you buy and then you'll know exactly what you are getting.


The lower price of £299 inc VAT means that this unit can be afforded by the majority of serious home studio owners, but I would have liked to have seen an even lower retail price if at all possible as the people who can benefit the most from these devices are those who are working on a tight budget using limited equipment. After all, some of the competition is selling for a fraction of the price such as the Tantek enhancer which is amazing value both ready built and as a kit. Even so, Aphex is the original and there are a lot of people who would rather stick with the original rather than choose another brand so Aphex aren't going to lose out.

Whether you prefer to call Aural Excitement an effect or a treatment is up to you but being a dedicated user, I would be loath to conduct a session without one. It's true that a perfect recording of a perfect performance should need no processing but limitations imposed by the recording equipment, the microphones and the performers themselves mean that this state of affairs is seldom if ever achieved. Another consideration is that a high proportion of the pop music we hear is processed by some type of enhancer and as pop music is an artificial medium, what we hear regularly eventually becomes the standard. To put it another way, if the accepted sound is an Aphexed sound... you are going to need an Aphex to make your music sound acceptable.

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Publisher: Home & Studio Recording - Music Maker Publications (UK), Future Publishing.

The current copyright owner/s of this content may differ from the originally published copyright notice.
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Home & Studio Recording - Jan 1986

Donated & scanned by: Mike Gorman

Gear in this article:

Studio/Rack FX > Aphex > Aural Exciter Type C

Gear Tags:


Review by Paul White

Previous article in this issue:

> Susstudio

Next article in this issue:

> dB or not dB

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