Test Drive: The ART MDC-2001 Stereo Master Dynamics Controller

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by Jerry Vigil

ART-MDC-2001

Appropriately named a Master Dynamics Controller (MDC for short), ART's new MDC-2001 packs all the dynamics processing you could want on one neatly designed, single rack space unit. You get what you would expect from a "dynamics processor" and more. This full stereo processor offers a compressor, a de-esser, an ex-pander, a noise gate, an exciter, and a peak limiter/clipper. Plus, there are two "detector" circuits with insert points that allow for some interesting effects. Add to this some exceptional specs and a modest price tag of only $499, and you have what could well be the best dynamics processor on the market for the price.

At the far left of the front panel are the controls for the compressor section. You get an INPUT control, a RATIO control, and controls for ATTACK and RELEASE times. The INPUT control sets the sensitivity of the compressor by adjusting the threshold from -40dB to +10dB. At +10dB, only levels above +10dB are compressed. Likewise, when set at -40dB, anything above -40dB on the input will get compressed. At full tilt, the compression is very clean. The range on the RATIO control is 1:1 to 40:1. The ATTACK time is adjustable from .5ms to 50ms. At the lowest setting, the attack is very quick and "punchy" with the compression level high. At the 50ms level, the attack time nicely smooths out the attack of the unit. The RELEASE time is adjustable from .1 second to one full second -- enough for most any application. Both the ATTACK and RELEASE controls also have an internal "Auto Adjust" feature which analyzes the dynamics of the incoming signal and "fine tunes" the two controls continuously.

The next knob we get to play with is the DE-ESSER LEVEL control. The de-esser function is pretty straight-forward. The range is from 0dB to 15dB. The more you crank it, the more the pre-set high frequency band is suppressed. The de-esser in the MDC is designed to remove sibilance when using large amounts of compression.

Next up we have the two expander controls. The THRESHOLD can be set from -50dBm to +20dBm and the SLOPE can be set from 1:1 to 1:5. This downward expander works in conjunction with the compressor and helps to reduce noise when there are lulls in the input signal. Its effect is most noticeable when using the MDC as a voice processor. With proper settings, pauses between words become dead silent even though large amounts of compression are being used and noticeable room noise is present. The THRESHOLD control sets the level at which the expander starts working. The SLOPE control sets the amount of work the expander does. Set at 1:3, a 1dB decrease in input below the set threshold will result in a 3dB reduction at the output.

Next to the expander controls are the NOISE GATE controls. Let's talk. There are more multi-track production rooms in radio today than ever before. Most are four and eight track rooms, and some are sixteen. Most of these multi-track rooms use analog recorders which result in more tape hiss and other noise being mixed into that spot or promo. Noise gates should be standard gear in a multi-track production studio (if outboard noise reduction is not in use), and it's wonderful to see this function on the MDC-2001. There are two controls for the noise gate: the THRESHOLD and the HOLD time. The THRESHOLD is adjustable from -90dBm to +20dBm, and the HOLD time is adjustable from 15ms to 2 seconds. The THRESHOLD obviously sets the level at which the gate will "open" and allow audio to pass. The HOLD time sets the time it takes for the noise gate to close once audio drops below the threshold. This control also sets the attack time of the gate. Noise gates -- if you've got 'em, use 'em!


Next stop on the panel tour brings us to the LEVEL and FREQUENCY controls of the EXCITER section of the box. The LEVEL control is adjustable from 0 to 10 and the FREQUENCY control from 4kHz to 15kHz. Audio first hits a high pass band filter and then enters an upward expander with a slope of 1:1.5. Highs are detected then boosted an amount set by the LEVEL control. The frequencies to be "excited" are determined by the FREQUENCY control setting. Not being a harmonic generator, this exciter circuit acts very much like an EQ section devoted primarily to upper mid and high frequencies. Its effect is very noticeable and functions well when using the box as a mike processor.

The PEAK LIMITER/CLIPPER control is just to the right of the expander controls. This threshold setting is adjustable from 0dBm to +20dBm and lets you set the maximum level you don't want the unit to exceed. The attack time of the limiter is 100 to 300 microseconds. When the level reaches 6dB above the set threshold, the "clipping" circuit engages.

The knobs to the far right of the front panel are the MASTER OUTPUT controls for the left and right channels. They can be set from zero output to +6dB gain.

Taking the LED tour of the front panel we have two GAIN CONTROL METERS, one for each channel. These two, twenty-one LED meters display a range of -30dB to +30dB. The center LED represents unity gain, and increase or reduction in gain is displayed by LED's lighting either to the right or left of this zero point. The meters remain active even if the unit is bypassed with the BYPASS switch. Two 8-LED meters above the OUTPUT controls are switchable between INPUT and OUTPUT and display the respective levels for each channel.

Yellow LED's above the EXPANDER, NOISE GATE, and EXCITER controls indicate that the thresholds of these functions have been exceeded and the indicated function is active. Two red LED's above the PEAK LIMITER/CLIPPER control indicate that the audio level has reached the threshold level set for the limiter. Finally, you get a BYPASS indicator which lights when the unit is bypassed with the BYPASS switch. By the way, not only can you bypass the entire box with the BYPASS switch, but each of the sections of the unit can be bypassed by setting certain controls to their minimum value. For example, to bypass the compressor, set the RATIO to 1:1. Set the de-esser LEVEL control to zero to shut the de-esser off.

Turning our attention to the back panel we find two left channel inputs, two left channel outputs, two right channel inputs, and two right channel outputs. The inputs and outputs are balanced, and you get either a ¼-inch (TRS) jack or the standard XLR jack for each. The unit may be used in an unbalanced setup.

The other jacks on the back panel are the DETECTOR LOOP input and output jacks, the GATE KEY IN jack, and the LIMITER LINK jack. You're right. These aren't common names of jacks on the back of processors you're used to. The LIMITER LINK jack simply lets you connect several MDC's together and have one MDC's limiter control the others.


Now, before we get into what the DETECTOR LOOP and GATE KEY IN jacks do, let's explain what this "detector" is. At the heart of the compressor in the MDC is a VCA or voltage controlled amplifier which is responsible for controlling the gain or reduction of the input signal. Instead of using the audio input to control the VCA, the MDC uses an external DC voltage to control the VCA. This external DC voltage is derived from a circuit that reads the input signal then converts it to a DC "control" voltage. This circuit is called a "detector circuit."

With this in mind, consider now that the MDC-2001 has four of these detector circuits. One is shared by the compressor and expander. The other three belong to the noise gate, limiter, and the exciter. The MDC-2001 lets you access two of these detector circuits: the one for the compressor and expander and the one for the noise gate.

The detector circuit for the compressor and expander is accessed via the DETECTOR LOOP jacks. Being able to control the compressor from an external source probably has several applications, but we only played with one the manual suggests. Let's say you have a busy music track that you're mixing a voice track with. Let's say the voice is so soft that you need to "ride" the levels of the music during the mix, "ducking" the music when the voice is there and kicking the music back up when as the voice pauses. By sending the music through the inputs and outputs of the MDC and patching the voice track through the DETECTOR LOOP, the "ducking" can be done automatically. Proper adjust-ments of the compressor controls resulted in a very smooth control of the music level with respect to the voice track. We tried the DETECTOR LOOP with a live mike and some music with impressive results. This could be the big fix for stations with jocks that can't seem to ride their music levels properly when talking over intros.

The other detector circuit you have access to is the one belonging to the noise gate. Patch your mike into the GATE KEY INPUT and the MDC becomes a voice activated noise gate that opens when you talk. Now, think of the many sounds you can have going through the MDC's audio chain while your mike is controlling the gate. When you consider that any line level audio signal can trigger the gate, there are lots of creative possibilities here.

The impressive specs of the MDC-2001 include a frequency response of 16Hz to 28kHz, a signal to noise ratio of -110dB, dynamic range of 120dB, and THD at less than .04%. Some of these specs you might attribute to digital processing, but the MDC-2001 is doing all this clean work in the analog domain. A.R.T. even incorporated an audio mute circuit that engages and disengages the outputs of the unit after it has been turned on and off and mutes the output for two to six seconds after power up.

A compressor. An expander. A noise gate. A de-esser. An exciter. A peak limiter/clipper. A full stereo processor. Clean enough to put in your transmitter audio chain. All in one box and all for $499. A.R.T. is proud to say that their design staff put some thirty years of cumulative compressor expertise to work to come up with what they feel is their best effort yet on a dynamics processor. We think they hit the mark. A.R.T. gets our nod once again. 

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