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Aphex Project Channel

Mono Channel Strip
Published December 2013

Aphex Project Channel

Could this offer all you need to get polished sounds from your mic to your computer?

Aphex's Project Channel is a mono channel strip that combines a number of the company's established circuits — their Class-A transformerless mic preamp, optical compressor, Aural Exciter and Big Bottom — in a single 1U rackmount device. For those who don't know about these long-established processors, the Aural Exciter adds a top-end sheen to any sources that need it, while the Big Bottom is a form of filtered parallel compression, which can be very effective in beefing up the low end of tracks and mixes. The compressor offers very simple yet effective one-knob adjustment for controlling vocal or instrument dynamics.


Starting with the preamp stage, there's a red LED clip-indicator to let you know when to back off the gain. A switchable -20dB pad allows the device to accommodate excessively 'hot' inputs, so there should be few, if any, real-life signals that the front end can't handle. Switchable 48V phantom power is provided for capacitor or other active mics and active DI boxes, and there's a 12dB/octave, 70Hz low-cut filter with which you can curtail any unwanted or uninvited lows. There's also the usual polarity-invert switch.

As touched upon above, the optical compressor can be set up using only a single ratio knob, which can dial in more or less compression. The key to operating this compressor is — as well as using your ears — to watch the 10-LED gain-reduction meter, as this gives a useful guide as to how much the dynamic range is being squeezed. With most compressors, the effect of applying gain reduction means you may need to make up the lost gain later in the signal chain using the output level control, but the way this one works (varying the compressor input rather than the threshold) actually increases the level slightly as you compress. A second meter, which displays the overall output level of the unit, is calibrated in dBFS. That's unusual in an analogue outboard device, but it's designed to indicate the remaining headroom when using the Project Channel's digital output. (Digital full scale corresponds to +24dBu at the analogue output.) Speaking of the digital output, a sample-rate button selects the four sample rates from 44.1kHz to 96kHz.

In the enhancement section, which has its own bypass switch, you'll find the Big Bottom and Aural Exciter processors, which both work to create a 'bigger' sound without generating any significant increase in level. The Aural Exciter uses the now-familiar harmonic synthesis method to generate new high-frequency harmonics from the existing material's upper mid-range. The Big Bottom processor inflates the lows via a combination of filtering and compression. Both of these sonic enhancers are parallel processes, which means that the processed sound is mixed in with the original signal. For both, care has to be taken not to over-process, as it's very easy to get carried away — and it's surprising just how quickly your ears can become accustomed to the enhanced signal. While the Aural Exciter can add top end where none was present before, the Big Bottom can only operate on what's already there. There's a 60 to 200 Hz frequency control that sets the low-pass filter feeding the processor, alongside an amount control. The Aural Exciter also has frequency (600Hz to 5kHz) and amount controls. The frequency control sets a high-pass filter that determines what part of the original signal spectrum is fed into the harmonic generator. You'll often find that lower frequency settings can sound quite aggressive, but don't let that put you off, as they're sometimes very useful for livening up dull snare drums.

It's worth pointing out that despite the inclusion of the Big Bottom facility, which, as Aphex put it "adds punch to your low end in a way that no EQ can” there is no conventional EQ here, other than the high-pass filter. Given that this is described as a channel strip, with "everything you need to get a fully sculpted signal”, that's a little surprising, as usually I'd expect to reach for EQ first before looking to more sophisticated processes such as this.


Given that all the elements that make up the Project Channel are derived from tried-and-tested Aphex products, it comes as no surprise that it works extremely well in practice. The preamp sounds airy and transparent (THD is under 0.05 percent), being only 1dB down at 30kHz. Although it's not deliberately coloured to sound fat and cuddly, adding a touch of the Big Bottom processing warms things up quite noticeably, if that's what you're after, so it's quite versatile in this respect. As for noise, the preamp can boast a similar spec to other high-quality front ends, with a quoted EIN of -126dBu (150Ω source, unweighted), though how quiet a mic preamp is at medium gain settings can often be more telling than how it measures when flat out. Importantly, in normal use I didn't notice any noise issues.

I already own an Aphex optical compressor pedal and I was told by Marvin Caesar, the original head of the company, that some users complained that they couldn't hear it working! In fact, that's testament to just how unobtrusive this style of compressor can be, even when the amount of gain reduction achieved is fairly high. It's designed to control dynamic range with minimal side effects, and that's exactly what both the pedal and the circuitry here do, with no appreciable loss of sonic transparency. If you need a gain-pumping monster then you need to look elsewhere.

To my ears, the effect of the Big Bottom process sounds not unlike the results of parallel compression, when the signal feeding the compressor is filtered to take out the highs. This has the effect of filling out the bass notes without adding much in the way of peak level. The Big Bottom facility works at both bass and lower mid-range frequencies, so it can be just as useful for warming up vocals as for the more obvious purpose of fattening up bass instruments or kick drums. On vocals it adds a really nice 'late-night DJ' sort of warmth. In contrast, the Aural Exciter is ideal for adding those intimate, breathy highs. Just don't push it too far, or the sound becomes brittle and 'glassy'.

The Aural Exciter has been around for over three decades now, and it can be extremely effective in situations where the source material doesn't have enough genuine high end for conventional EQ to get its teeth into. The upper harmonics that it adds are inherently musically related to the source material, so the human hearing system accepts them as being natural. However, as I hinted earlier, the effect is incredibly easy to get used to, and this means that it's vitally important to keep checking against the unprocessed sound to make sure you haven't gone too far. If you need to add air to a miked vocal or zing to an acoustic guitar, a little of this effect goes a long way, and while testing this unit I found that a setting of around half way on the amount control was often enough. It can also be useful in rescuing old analogue tapes that have dulled with age or for winding back the clock on those old acoustic guitar strings.


There's no doubt that this box delivers exactly what it sets out to, and at a sensible and affordable — if not exactly 'budget' — price, too. The preamp, compressor and enhancers all deliver the goods and are easy to use. The lack of EQ wasn't a huge problem for me. Given the primary market at which this is aimed, most users will already have access to software EQ in the box, and the Big Bottom and Exciter functions serve to plug the EQ gap in some respects. But when comparing with other channel strips, the lack of EQ must be balanced against the other elements of the equation.

As with any channel strip, whether it's the right choice for you will depend very much on how you prefer to record and mix. If, like me, you like to record everything clean and then process afterwards, the preamp stage will do what you need, but you may not derive the full benefit from this format unless you have the means to patch in the unit when mixing so that you can use its processing sections at the appropriate time. If you prefer to commit to at least some processing decisions as you track, then it should have broader appeal — unless you overdo things with the enhancement, you're not going to leave a huge sonic fingerprint on the recording. For the same reasons, I can see this box appealing to some live sound engineers.

Of course, when it comes to mixing, the various processes in this channel strip have their software plug-in equivalents, but there remains something endearingly 'organic' about the sound of the analogue versions, both for the exciters and, especially, when it comes to compression. That being the case, it may well be worth applying some compression as you record. Just make sure you err on the side of underdoing it, as you can always add more using plug-ins, but you can't reduce it if you add too much!

On balance, then, particularly given that the digital output is included, the Project Channel represents decent value for money, and should hold plenty of appeal for home- and project-studio recordists.


While there are viable alternatives to all of the processing sections in this unit, both in hardware and as plug-ins, this is the only unit I know that puts them all in one box.

The Ins & Outs

The rear-panel hosts the XLR mic input, a balanced XLR analogue output, a quarter-inch analogue TRS jack output (which is switchable from +4dBu to -10dBV) and a 24-bit S/PDIF digital output, presented on an RCA phono connector. S/PDIF is a two-channel format, of course, but this is a single-channel device, so identical mono signals are sent to both S/PDIF channels. Connectivity to the Project Channel also includes a quarter-inch, high-impedance instrument input on the front-panel, which overrides the rear-panel input. There's no dedicated line input, although you could get away with feeding line-level sources through the instrument input or the padded mic input. Power comes from an integral, universal voltage, switch-mode power supply that has a soft start-up to avoid pops and bangs. Mains power is fed to the unit via a standard IEC mains inlet, and a suitable IEC mains cable is provided.

Published December 2013

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