ART MDM8L

Paul White tries out ART's new 'digital safety net', and discovers it has a great deal of creative potential.

The great thing about digital recording is that it doesn't suffer from the colorations and non‑linearities of analogue tape — what you put in is pretty much what you get out. The bad thing about digital recording is that — well, it just doesn't sound like analogue, does it? On a more practical level, digital recording means that you have to take care never to overcook your recording levels. What might sound like a pleasing hint of overdriven warmth on an analogue machine can sound like a blender full of broken glass on a digital recorder.

ART's MDM8L 8‑channel analogue compressor/limiter sets out to solve both sets of problems at a stroke — it uses limiters to keep an eye on your recording level, and it adds compression to emulate the warmth of analogue tape saturation. It can't reintroduce wow and flutter, and it doesn't promise to bring back tape hiss, but then there are some analogue 'benefits' that you can well live without!

Technically, the MDM8L is simply eight compressors in a box, each channel also incorporating a separate, fast peak limiter. As with any other compressor, the channels of compression may be used separately as stereo pairs, or up to eight channels may be linked. In Manual mode, the front panel controls are used to set the input gain (and hence the amount of compression), and the output level or makeup gain. There's also a second mode, termed MDM (Modular Digital Multitrack), which is accessed by a the Mode button adjacent to the main switch. This mode sets the output level ceiling of all eight channels, and brings in the compression some 6 to 8dB below the limiter threshold, adding a touch of warmth. You are most likely to use this second mode if you want the MDM8L to protect your digital multitrack or hard disk recorder from overloading. In this mode, a rear panel master level switch sets the desired output level: ‑10dBV for unbalanced systems and +4dBu for balanced.

Layout

Powered directly from the mains, the MDM8L comprises eight identical channels, each of which has an Input Level control, an Output Level control, and a Bypass switch. All but the first channel have Link buttons which tie that channel's operation to that of the nearest unlinked channel to its left. Both the Bypass and Link buttons are fitted with status LEDs.

The unit offers no control over attack and release time, or a separate threshold control for the compressor and limiter. As far as I can tell, the thresholds are linked so that the compressor always comes in a few dBs before the limiter, and the compression ratio is preset at 2.5:1. The attack time for the compressor is set at 1.5mS to allow a little overshoot (for the sake of character), while the limiter is much faster at 100 microseconds, although the compressor release time appears to be programme‑dependent and varies from 100mS to 2S. The Input Gain control has a range of +20dB to ‑40dB and is used to set the signal level against a fixed threshold, a status LED indicating when gain reduction is taking place. The Output control provides +/‑20dB of gain control when in Manual mode, but is inoperative in MDM mode to prevent the preset maximum signal level being exceeded; control over the output level in MDM mode is only possible via the rear panel master output level switch, situated between the jack sockets and the mains inlet. This is, in turn, inoperative in Manual mode.

Although the signal connections are on jacks only, they are all electronically balanced, both inputs and outputs. Even though the compressors have few controls, ART have designed them to sound musically useful over a range of applications — the MDM8L is most definitely not intended simply as a nursemaid for your digital multitrack. The linking option means that stereo signals can be treated without the stereo image wandering all over the place, and the programme‑dependent release time is designed to ensure that the compression sounds as natural as possible, regardless of the dynamics of the incoming signal. On paper it sounds great, but what's it like in practice?

Testing Times

It's quite clear that the MDM8L was designed for the benefit of the ADAT and DA88 user, so I patched the unit in line with the input of an ADAT and set about feeding it signals — both individual tracks and complete mixes. MDM mode proved to be quite accurately calibrated for ADAT use; compression starts several dBs before you hit the end stops, and the limiter steps in just as clipping is about to occur. Of course, the input gains can still be used independently, allowing more compression on some channels than others — it's just the peak levels that are kept the same.

Used discretely, the compression and limiting is reasonably transparent, but as you pile on more gain reduction, the compressor action becomes quite audible, starting out as a warm thickening of the sound, and eventually resulting in an obvious pumping effect. I actually rather like the pumping effect, which helps add to the illusion of power and dynamics on rock tracks or strong vocals. As there are so few controls, the MDM8L is incredibly easy to set up — you simply use the input gain control to set the amount of compression you want, and though you don't get any fancy gain reduction meters, it's pretty easy to set the required degree of processing by ear. The only disadvantage of not having metering is that you might end up piling on more compression than you really need, with the inevitable result that any background noise in the source material is also raised. At least the Threshold LED lets you know when gain reduction is taking place, but I'd have been happier if ART had fitted a limit indicator LED as well, so that you could see when the limiter joins in the action. As it is, you get to see when the compression starts, but that's it.

Conclusion

As a general purpose compressor, the MDM8L is surprisingly flexible considering its simplistic control system. It is very effective at fattening sounds, as well as simply keeping their peak levels under control. In MDM mode, the unit allows you to get maximum level onto digital tape, which in turn helps squeeze the best resolution from the digital format, and at the same time it means you don't have to keep worrying about clipping. In a live recording situation, this feature could be a life‑saver, as performance levels never match up to what you hear during the soundcheck.

Ever since affordable digital multitrack came along, I've been nagging various manufacturers to build a simple 8‑channel limiter, so now that such products are starting to come on line, I'd better confirm that I still think it's a good idea. As it stands, the MDM8L provides very effective insurance against clipping, but I have to admit that I was also pleasantly surprised by its creative potential when driven hard.