Aphex Systems 230 Master Voice Channel
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by Barry Rudolph
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Aphex Systems 230 Master Voice Channel The Aphex Systems 230 Master Voice Channel is a "medley" of Aphex's greatest hits--eight wonderful analog processors optimized for the human voice in a single, easy-to-use 1U unit. For radio/TV work, record productions, and live sound, the single-channel 230 is designed as a complete system to help any voice sound bigger by making it denser, louder and more dynamically consistent.

Under The Hood

The road-worthy 230 is well built and housed in an all-steel case with a separate switching power supply, main circuit board and a 12AT7 (sourced from Ruby Tubes) mounted horizontally and "capped" with a spring-loaded heat sink/retaining mechanism made of copper. The 230 uses well-damped pots and proper, finger tipped-sized lighted push buttons for all controls and switches.

Front Panel Controls Simplify Complex Processing

Processor 1

The left side of the 230's front panel starts with the power on/off switch and the Gain/Drive control. Gain/Drive directly controls mic gain and the following compressor's action at the same time. A 12AT7/ECC81 is configured in Aphex's RPA (Reflected Plate Amplifier) Tube Mic Preamplifier™ circuit where a constant and very low plate voltage of around 30-volts is used to maintain electron migration and transconductance. That small plate current change is "read" or reflected into an external solid-state circuit to derive audio output and gain.

RPA is a way to get the warm and colorful sound of an all-tube mic pre-amp without the bulk, power supply requirements, transformers and the extra expense of manufacturing a typical tube mic pre-amplifier.

The mic pre-amp section has a switchable -20dB pad, 48-volt phantom on/off, polarity invert, a clip/mute LED and a 12dB/octave high-pass filter starting at 70Hz and with a slight boost at 120Hz.

Processor 2

Following the mic pre-amp section comes the Phase Rotator switch. This is a pre-set version of Aphex's Spectral Phase Refractor technology especially tuned for vocal frequencies. SPR reduces the level of asymmetrical voice peaks by shifting the timing (phase) of the harmonics relative to their fundamental. The net result of this psychoacoustic enhancement is not like equalization but an extension of highs and lows with an increase in clarity.

Processor 3

The mic pre-amp's signal is passed on to an abbreviated version of the Aphex's Easyrider™ compressor and followed by a Logic Assisted Gate™ and a De-Esser section. The compressor, gate, and de-esser detector circuits control two Aphex 1001A VCA chips whose outputs are summed together.

The only compressor control is the Release knob--any compression action from aggressive, using faster release timing, or more natural and open sounding using slower release times, is set here. A button toggles the dual scale LED peak/GR meter between reading peak output level or gain reduction.

Processor 4

The Logic Assisted Gate seems deceptively simple with just two controls, Threshold and Depth. But again it has been especially designed to deal with any background noise riding in on live vocal microphones.

Processor 5

The De-Esser section has a single Threshold knob and "looks" at the signal from the mic pre-amp after it has passed through a phase-coherent crossover at 5kHz. The subsequently developed de-esser control signal is used by the second VCA chip.

Processor 6

Next in the chain is Big Bottom®, a well-known bass enhancement processor that uses an opto-isolator compressor circuit. Boosting bass with a common equalizer generally sounds more like the EQ unit itself rather than the low frequencies you'd like to boost. Big Bottom, using the Tune control, allows for "tuning in" the exact bass frequencies to enhance. You can boost the "chesty" areas of the voice without increasing muddiness.

Processor 7

Just in case there is a nasty frequency peak in the vocal's sound or you'd like to do a special EQ boost or notch effect, the 230 has a single frequency fully parametric equalizer. The Frequency control ranges from 240Hz to 4.5kHz, the Q or bandwidth ranges from 0.5 to 5, and you can boost/cut up to 12dB.

Processor 8

Rather than adding a high frequency equalizer section, the 230 has Aphex's classic Aural Exciter®--a processor for increasing clarity, presence and loudness. The Tune knob ranges from 600 to 6kHz. Lower Tune frequencies augment presence and higher settings bring more "air" to the sound.

A single push button toggles the Big Bottom, Equalizer and Aural Exciter sections in or out as a group; there is no panel space for separate in/outs for each processor.

Pro Rear Panel

The 230 has three XLRs for: microphone input (you can run hotter line levels into it if you use the 20dB pad); an analog line out (up to +25dBu); plus an AES/EBU digital output. The 230 uses an AKM A/D chip set with rear panel slide switches for setting up to 96kHz sample rates at 24-bit depths.

There are also S/PDIF RCA and TOSLINK spigots, BNC Word Clock In/Out jacks and internal/external clock switching. Lastly, there are 0dB balanced effects in/out TRS jacks (inserts just after the mic pre-amp output) and a Cough/Profanity switch jack for live broadcast applications.

The 230 To The Rescue In The Studio

For some at first glance without knowing anything, the Aphex 230's front panel may appear daunting. I familiarized myself with the sound and effect of each of the eight processors by first running vocal tracks from my Pro Tools HD rig.

I used the digital TOSLINK optical output and externally clocked the 230 (along with the Digidesign HD 192 I/O) from my Benchmark Media ADC1 A/D converter.

Initial Comments

One of the first things I figured out was that arriving at a good record level was like other compressors: a balance between the Gain/Drive and the Output level controls. If you like to squash hard be ready for a concomitant increase in output as Drive/Gain is wound up. Although in general the output level remains fairly constant through a fairly large range of panel settings--a good thing for live sound work I reckon. Check the manual for a good setup procedure.

I found the Release control to completely control the nature and "vibe" of vocal compression. Obvious pumping DJ vocal sounds are easy: wind up the Gain/Drive and use a short Release time and your done. Smoother more natural voice recordings come with slower release times--even at deep compression amounts.

The Lo Cut filter is very effective--it may roll out too much bass depending on your preferences but becomes a necessity when you discover the Big Bottom processor section's power. My studio is not especially isolated from super loud noises outside so I found Lo Cut to work well to get rid of street rumble and also decrease microphone proximity effect.

A unique feature of the gate is that when it closes, the compressor's release time expiry (and therefore) gain reduction is "frozen" at its last state. This way the gate will not see the noise floor brought up (as normally happens with other compressors) and re-open it. This intelligent link between the two processors prevents them fighting one another.

Essentially a mid-range setting for the Depth control worked best. I dialed in the Threshold until the background noise was gently subdued without "gating" artifacts.

Let's Do A Voiceover

For my evaluation, I had my male voice talent read the same paragraph at the same consistent volume and energy many times while I tweaked and recorded different settings and combinations of the eight processors.

I set up a Gauge Precision ECM-47 tube condenser with windscreen and began listening to each of the processors one at time beginning with just the RPA microphone pre-amp only. I found the mic pre-amp to sound clean and free from any coloration--a great starting place for more processing.

Engaging the Phase Rotator brought on a "taller" sound that my voice artist preferred immediately. It is hard to describe exactly what the Phase Rotator does but we liked it! All pre-amps should have Aphex's Phase Rotator control and maybe a variable impedance knob too!

In our first recordings, we were going for a fat and distinctive male sports announcer sonic footprint. I discovered my voice talent naturally had very little of the characteristics necessary for that sound so I used Big Bottom as well as the rest of the 230's processors to help him out.

The Lo Cut filter lessen both "P" pops and external traffic rumble that BB will bring up. Compared to most high pass filters on mics and pre-amps, Lo Cut is drastic yet, with that resonant peak at 120Hz, vocals don't sound filtered and thinned out--there is still plenty of low frequency information left.

With Big Bottom's Tune control, I found a band of frequencies that made my talent sound at if he were a foot taller and three suit sizes bigger--especially in the chest measurement. We ended up using BB tuned to the lowest setting at around 80 to 120Hz but it does not sound like an EQ bump at that frequency at all.

Since BB is after the compressor, using it does not cause additional gain reduction. I went for about 4 to 8dB of compression indicated on the LED meter and set the Release control at 3 o'clock, a fast setting that made the voiceover aggressive and slightly pumping sounding.

I had little need of the De-Esser but I could see that it was grabbing normally and did tame the major egregious sibilants. The parametric equalizer added upper midrange cut frequencies the compressor had slightly shaved off. This proved to be just the ticket to increased intelligibility.

I found a little of the Aphex Aural Exciter section went a long way on this artist. I went for "air" of the sound and set the Tune knob to 6kHz. The Mix knob ended up at about 11 o'clock position after a lot of listening. The AE has a lot of range to brighten up any sound but if over used, it will sound strident. A slight brush up of this effect is perfect.

The moderate learning curve for the Aphex Master Voice channel paid off with greatly improving the sound of my voiceover artist. If you record several different people, I'd get a front panel recall sheet for each person's unique settings.

Excellent Anything Channel

I think Aphex might be unnecessarily constraining the 230's abilities by calling it a "Master Voice Channel." Clearly this unit is a "Swiss Army knife" of an audio problem solver--a very thick knife with a lot tools and blades. I like the whole concept of the unit and feel like I'd always want this in my rack for problem sound sources I'm often asked to make sound better and fit into a track.

I'd like to see separate compression drive and pre-amp gain controls if there is front panel room and also like to see the De-Esser detector selectable between pre and post EQ/Aural Exciter processors so that even brighter sounds could be recorded with an absolute high frequency "lid."

A big recommendation from me on this one! Aphex Systems' Model 230 Master Voice Channel sells for $995 and for much more check: www.aphex.com.

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