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Logic with a light touch

Aphex 105 noise gate

Article from The Mix, August 1994

More gates, fewer greenbacks

Not all of us want to study acoustic theory just to tidy up a home demo. But is the user-friendly, logic-assisted Aphex 105 noise gate the answer? Bob Dormon discovers that opening a gate doesn't necessarily frighten the horses...

Noise gates, dontcha just love 'em? An indispensable aid to making something dodgy sound decent. The usual problem we engineers are faced with is that there's not enough to go around. The option to gate recordings that have begun in a less than perfect environment or been under-recorded, is more than welcome. To live up to their name, noise gates must have respectable circuitry, as their general function is to sort out the men from the noise - adding to it is inconceivable, if the designers want to stay in business!

Bearing in mind that a good mix will enjoy well defined instruments and players, then the noise each track contributes will affect the overall clarity. Some might claim that they like a bit of grunge, but sometimes it's an excuse for an unprofessional product made up of sounds they've nicked because they can't play a note themselves. If you like noise, why not record on a wax cylinder? It was good enough for Queen Victoria, after all.

Basically, gating is good. It's only bad when it has been done badly. They have a simple enough function, but it takes a certain amount of time and patience to set things up properly. Aphex have simplified their function still further.

Form & function

Their model 105 Logic Assisted Gate has only four knobs and one button per gate. The back panel offers the option of +4dB or -10dB operation for each gate, with balanced 1/4" jack sockets for input and output, plus key trigger inputs. It's what you'd expect to find round the back, but the front panel is somewhat light on features. But there's a good reason for it. It's the fact that there are four noise gates in a 1U rack here. The Aphex model 105 is not intended for esoteric use, it's just four gates banged in a box to use on recordings and mixes that need help.

This functional approach reminds me of a similar batch of gates made by Glockenlang. While the faithful Drawmer 201s nestled in the studio rack, the additional Glockenlangs were worth their weight in gold. They were able to deal with the less dynamically challenging sound sources such as drums, or dubious individual outputs from less than perfect samplers. I can see the Aphex 105s taking on a similar role, and not only in studios but for live work too.

The eight page manual/pamphlet reinforces the fact that there's not much to this unit. However, I feel the 'logic assisted' description warrants a fuller explanation.

A short paragraph defines the process as having a 'peak stretch' circuit in the detector system that magnifies the difference between peaks. It's supposed to assist in setting the threshold, so that the gate doesn't trigger when you don't want it to. In practice, this worked well for short lived signals, but posed problems with sustained sounds; dipping out and then opening again before finally closing.

This is a typical problem encountered when gating such signals. Altering the hold and release times didn't compensate entirely for it, especially for a guitar that needed to be gated tightly but needed a certain amount of freedom of expression.

The Model 105s logic assisted circuitry appears to be a cut down version of the Aphex 622 Expander/Gate. The 622 boasts an attack time of 4µSecs whereas the 105 has a distinctly lazy 200µSecs.

"You can either gate or have a light pseudo-expansion of the signals that enter the Model 105 and that's it"

Standard Threshold, Attack, Hold and Release controls for each gate


All four gate channels have identical functions. The sixteen black plastic knobs have a positive rubberized feel to them, improved by their grooved surface. Each knob sports a grey plastic wedge that conveys the current status of each control. The white panel legend shows figures for the minimum, central and maximum settings of each function. This is assisted by the light grey lines that run across the whole panel, offering a form of graduated scale.
The speed of the latter will no doubt prevent clicking when the gate opens, but could prove to be a touch too retarded for retaining the attacks of percussive sounds.
Above the description of each knob, a violet strip clearly divides the controls for each gate. Below each gate are three LEDs which indicate when it is open, closed or if the key trigger input is being used. The key trigger LED is somewhat misleading as it will light whenever there is a jack inserted into it. This may prove to be a problem if this unit is to be wired into a patchbay, as the jack will switch the gate into external key mode.

Trying a number of normalizing combinations with both stereo and mono jacks didn't succeed in extinguishing the external key trigger LED. This, combined with the minimal functions and the external 24volt AC PSU, suggests that Aphex do not consider this unit suitable for use with a patchbay in a semi-pro environment.

This approach is emphasised still further by the limited range control. It's a single button that toggles a gate's attenuation by 90dB or 6dB. You can either gate or have a light pseudo-expansion of the signals that enter the Model 105, and that's it. There's nothing in between, and no stereo linking available.

In use

In isolation, the -6dB range isn't very appealing. The manual suggests that if used on microphones in a multiple PA conference situation, then feedback can be reduced " as much as 50%.". I was unable to test it in this context, but I did find that being able to pronounce signals (such as snare and bass drums within a loop) with this setting actually worked quite well when heard with the rest of the song, despite initial misgivings about its effect.

The threshold control caters for signals from -50dB to +20dB and careful adjustment of this control allayed my fears about the attack time on percussive sounds. A longer hold time would have been preferable, especially on awkward sustained sounds - altering the release values to compensate defeats the object of using a gate! The release time itself is variable from 100mS (although the front panel says 150mS) to 4secs, and the gate closed swiftly enough for this relatively slow setting to be acceptable.

+4dB or -10dB operation is available on all four channels


The Aphex 105 is a simple but effective gating workhorse, which was never designed to work the same kind of miracles as its big brother the 622 or the industry standard, the Drawmer 201s. The unit gets remarkably hot around the AC input, to the point where it is uncomfortable to touch. So don't rack it up next to a Proteus or you'll melt the thing!

A stereo link option and the ability to bypass the gate (and the key trigger) would have been welcome implementations, but I suppose it complicates matters. After all, it's easy and simple to use, and makes the difference between dodgy and decent demos for the non-automated home recording enthusiast.

The essentials...

Price: £410 inc VAT

More from: Stirling Audio, (Contact Details)

Their spec

No. of channels: Four
Frequency response ±0.1 dB: 17Hz to 20kHz
THD @ 1kHz: 0.005%
Crosstalk rejection: Better than 90dB 20Hz to 20kHz
Attack rate: 200pSec to 120mSec
Hold range: 1mSec to 1Sec
Release rate: 100mSec to 4Sec
Threshold Span: -50dB to +20dB
Dimensions: 482mm x 44.4mm x 132mm
Net Weight: 2.27kg

On the RE:MIX CD

The Aphex 105 is one of the noisegates Bob Dormon uses in his noise gating tutorial on this month's CD.

- Noise-gating tutorial.mp3

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Three of a kind

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Publisher: The Mix - Music Maker Publications (UK), Future Publishing.

The current copyright owner/s of this content may differ from the originally published copyright notice.
More details on copyright ownership...


The Mix - Aug 1994

Donated by: Colin Potter

Coverdisc: Mike Gorman

Control Room

Gear in this article:

Studio/Rack FX > Aphex > 105 Four Channel Gate

Gear Tags:


On The Re:Mix CD:

36 Noise-gating tutorial

This disk has been archived in full and disk images and further downloads are available at - Re:Mix #2.

Review by Bob Dormon

Previous article in this issue:

> Three of a kind

Next article in this issue:

> JBL MR825

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