Field Report: Aphex Model 230

March 1, 2007

It was time for KSON and KIFM in San Diego to embrace the digital age of HD Radio. In this march forward, we needed new, simple microphone processing that meshed with our new digital console and air chain. After many listening tests, we selected a processor that had the warmth of old and integrated with the new digital of today: the Aphex 230 voice processor.

Installation of the 230 is straightforward. The rear panel features an XLR mic input with a graphic warning of the potential of 48V phantom power. Next to the mic input is an effects loop, which is not normally used in a broadcast environment. The send and return are both ¼" balanced TRS jacks labeled for 0dBu. There are two line outputs: a male XLR +4dBu and a ¼" TRS phone jack that is run unbalanced -10dBV. Both outputs can be used simultaneously if the need arises. There is also a ¼" TS cough switch jack if needed.

Performance at a glance
Low-noise RPA tube mic preamplifier
Logic Assisted gate
Includes Big Bottom bass enhancer and Aural Exciter
High-resolution 24/96 A/D converter

The rest of the rear panel is dedicated to digital. There are three digital outputs: An XLR AES, a coaxial RCA S/PDIF and an optical TOS output. Beside the output jacks are two switches that choose the sample rate. The first switch designates 44.1kHz or 48kHz sample rate while the second switch is a multiplier being one or two. Thus, in addition to the 44.1kHz and 48kHz it provides 88.2kHz or 96kHz sample rates. In our facility 44.1kHz is the house rate. These are the internal sample rates. If you prefer to use a central word clock you have that option. Choose the switch for internal or external clock, and if you use an external clock you have BNC connectors for word clock in and out. The 230 will sync to frequencies between 32kHz to 96kHz.

The front panel is loaded with the controls of the processor. All switches and knobs are logically located making it easy to visualize the flow of the signal. A power switch is provided on the front, which I find useful in situations when access to the back is difficult. The switches for low cut, 48V phantom power, polarity, the phase rotator and a 20dB pad are at your fingertips. A switch is provided to engage the compressor. With a single switch you can turn on the equalization processing of the Big Bottom, the parametric EQ and the Aural Exciter. There is no switch to engage/disengage each effect, nor does the gate or de-esser, but the de-esser is essentially shut off by setting the threshold to +24dB.

Delving deeper

The first stage comprises the RPA tube preamp and the Easyrider compressor. The tube used is a 12AT7/ECC81 dual triode. Input control is the combination gain and drive that sets the gain of the preamp and the drive to the compressor. This is graduated from 20 to 70. The release knob, with a range from slow to fast, controls the density of the compressor. With the proper combination of gain/drive and release, the compressor is smooth and controls the levels well. I opted for a middle-release level. To monitor the amount of gain reduction there is the dual purpose LED meter. A switch is used to view VU or gain reduction.

Following the compressor is the gate. Unlike many gates, this is the patented Logic Assisted Gate. I tried many different settings. I could not get this gate to chatter; a problem we had with our older microphone processors. With this gate all you set is the threshold and depth controls. The threshold ranges from -40dB to 0dB and the depth can be set between -2dB and -65dB. If the depth control is set too deep you get the noise on/noise off sound that I dislike in gates. This can be avoided by seting the depth to no more than 12 o'clock — around 6dB.

The other unique stage is the equalization stage that follows the gate and de-esser. Unlike traditional parametric equalizers with level and bandwidth controls for three bands, you are presented with the Big Bottom bass enhancer, a parametric EQ and the Aural Exciter. Even if you are not fans of these controls, I found that with a little play and minor adjustments they work better than a basic equalizer. The Big Bottom is set with a tune knob and a mix knob, likewise the Aural Exciter. The Big Bottom frequency tuning range is from 80Hz to 300Hz, and the Aural Exciter has a range between 600Hz and 6kHz. Both feature mix controls that range from zero to max.

The parametric EQ came in handy to smooth out any annoying frequencies with its frequency control, Q (bandwidth) control and gain control. The frequency range is from 240Hz to 4.5kHz, the bandwidth ranges from .5 (broad) to 5 (narrow), and the gain, or peak/dip, ranges from -12dB to +12dB. I ended up dipping a moderately wide bandwidth for the room, which allows the voice to be more natural.

Aphex Systems

This is a new installation, and I have not run into any maintenance issues. One concern I had was installing a tube-based device. According to Aphex, the patented tube circuit has been in thousands of units for more than a decade with fewer than a handful of failures. Even if I had to change a tube, it would be a small price to pay for maintaining a unique and quality sound. At the same time, when deciding where to place this unit, or multiple units for that matter, there is a heat load to be aware of. My units are enclosed in racks that provide sufficient ambient air flow. To help maintain the free flow of air I installed vented rack panels above and below each unit. As for doing any maintenance on the 230, there is no schematic provided, and if the unit is in bad shape you need to send it to the manufacturer.

I find the Aphex 230 to be a great addition to our air chain. My basic requirements were met when I was able to get a quality microphone processor with a digital output. The performance of these units over the past year has been quite good. The price was competitive, too. There is always a risk when you are one of the first to use a piece of equipment, but I felt confident that this one would work. It has.

Eisenhamer is the staff engineer for Lincoln Financial Media in San Diego.

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