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Aphex 109

2/4-band Valve Parametric EQ By Paul White
Published September 1996

Aphex continue to attack the market with their high quality, value for money processors. Paul White warms to their latest release.

Regular readers will already know that I don't favour the indiscriminate use of EQ, and when I do have to use it, I do so as sparingly as possible. There are, however, occasions when you do need an EQ setting that will grab a sound and shake it by the scruff of its neck. In most of these cases, the type of EQ section you find on a typical mid‑priced mixing desk is somewhat underpowered for this task — what's required is a good parametric equaliser. However, cheap parametrics tend to disappoint while the really nice ones leave you with a significant deficit in the arms and legs department. And if you want a good sounding valve parametric, you'll probably have to call in your friends to contribute a few limbs, because prices more or less double when you put valves inside things.

In that light, you can probably understand why I did a double take when I first saw the Aphex 109, with its VAT inclusive retail price tag of under £400.

Enter: Stage Left

The 109 is a 4‑stage parametric EQ which can be configured either as a mono 4‑band unit or a stereo 2‑band device. At the heart of the unit is Tubessence, Aphex's low voltage valve‑based hybrid circuit that employs an ingenious solid‑state feedback system to make the valve behave and sound like a conventional valve circuit being run from around 300 volts. Tubessence has been included in a whole range of products, including the 661 Expressor reviewed last month, and the general consensus is that it really does work.

With balanced ins and outs on TSR jacks, and switchable ‑10/+4dBu operating levels, the 109 occupies a scant 1U of rack space and is powered by one of those irritating external power supplies. I don't really like external PSUs, but at this price I'm prepared to make an exception.

The controls are set out as two identical stereo channels, each with an input gain control and two fully parametric EQ stages. Band 1 is variable from 20Hz to 2kHz and may be switched from the usual band‑pass mode to a high‑pass shelving filter if required. Band 2 covers 200Hz to 20kHz and may be switched for band‑pass or low‑pass filter operation. Each section has a gain range of plus or minus 15dB, and a bright red Clip LED lets you know when you're running too hot. This is an intelligent indicator that monitors three discrete points in the signal path and lights up if any one of them comes close to clipping.

In the centre of the box are two buttons: Mode switches from 2‑band operation to 4‑band (whereby Channel 2's input and Gain control are disabled), while Process acts as a hard bypass switch for the whole unit, routing the inputs directly to the outputs. There are no separate bypass buttons for the individual bands, but the Cut/Boost controls are centre‑detented so that the unit can be run flat, allowing Tubessence to work its magic without the signal necessarily being EQ'd.

Alive And Kicking

From the previous description, you will appreciate that the 109 is a very straightforward equaliser, but the addition of shelving/band‑pass switching adds to its flexibility enormously. In practice, I usually find that a 2‑stage parametric EQ is adequate to meet most studio needs, and in the case of the Aphex 109, that means you can treat stereo signals such as whole mixes or subgroups quite effectively. However, you can easily throw all four sections into use to treat any difficult mono signal, when required.

While the controls of the 109 hold few surprises, the tonal quality certainly does — excluding certain top‑flight models, the 109 is simply the nicest parametric I've used at anything like the price. On bass signals, you can really pile on the warmth and depth without seeming to upset the tonal balance, while at the top end, you can add so much sizzle that it's hard to believe you haven't got hold of an Exciter. Wherever you tune it, this equaliser is smooth, positive and very polite with none of the honking, phasiness or harshness that some designs seem to inflict on you. In band‑pass mode you can lift or cut selected frequency bands with considerable precision, while shelving mode allows you to make more gentle changes reminiscent of a really good console EQ. And you can combine band‑pass responses in one band with shelving responses in another, whenever you need to, for added flexibility.


In the 109, Aphex have built a truly musical‑sounding equaliser that combines flexibility with simplicity of operation. It sounds silky smooth on vocals, yet you can add enough top end boost to make things really sizzle if you need to, and bass guitars can be given extra depth without them sounding flabby or uncontrolled. Though you can buy better sounding equalisers, you have to pay a lot more than this for them, and in this price range, I can't think of anything to rival the 109. Unlike most low voltage valve circuits, the Aphex hybrid approach doesn't compromise the transient response or sense of top end 'air', yet it's as quiet as a quality solid‑state design. If you're in the market for an outboard EQ, this is one unit you really have to try.


  • Versatile and easy to use.
  • Warm, detailed sound.


  • No individual band Bypass switches.


A great‑sounding valve parametric EQ that rivals the cost of budget solid‑state models.