Sound Mixing, Amplification and Processing

Audio Processor dbx DDP Digital Dynamic Processor also for sale


Possibly the best known manufacturer of analogue dynamics processors -- compressors, gates, de-essers and so on -- dbx have employed the all-conquering binary bit in their first stand-alone digital dynamics machine, the DDP. The name is a contraction of Digital Dynamics Processor, and that's exactly what the unit is, so why not?

Rather than merely producing a digital replacement for a conventional compressor or gate, what dbx have created in the DDP is an amazingly powerful and compact multi-function processor, a machine which can perform up to five dynamics functions simultaneously on a stereo signal, or four processes on each of two independent mono signals.

The DDP offers a number of preset processing configurations: two stereo setups, six dual-mono configurations, or one single-channel mode with external side-chain keying. The sequential order of the dynamics processes can not be altered, but the options (in the prescribed input-to-output order) are:

3-band parametric equaliser (inserted in the side-chain in some configurations)





There is also a sixth block, which uses channel 2's input to drive the side chain of channel 1, enabling external keying and ducking.

The DDP is a typical 1U rackmounting device with the traditional black paint finish and a very readable yellow back-lit LCD window in the centre of the front panel. A large data-entry knob and function select buttons cover the right half of the panel, while the left features input and output level controls with associated bar-graph metering.

The rear panel is just as straightforward, with XLRs and TRS quarter-inch jacks provided for the electronically balanced analogue inputs and outputs. There's also the obligatory pair of MIDI In and Out/Thru sockets. An optional digital I/O module is available (but was not fitted to the review model), providing AES-EBU and S/PDIF interfaces at 24-bit resolution and 44.1 or 48kHz sample rates.

Analogue inputs and outputs are converted at 24-bit resolution with a quoted dynamic range of 105dB (A-weighted). However, dbx have incorporated a sophisticated soft-limiting function in the A-D stage, and this is claimed to increase the effective dynamic range significantly. The so-called Type IV Conversion System is supposed to prevent brief input overloads from transients turning nasty in that familiar way that digital equipment has, and, using this system with suitable transient-rich material, the specs claim that the usable dynamic range is something more like 122dB (A-weighted).

Unusually, there is a built-in calibration routine to align the A-D converters, although the manual offers no suggestions as to how often this needs to be done, or what audible degradations may be observed when the converters require re-calibrating! However, during the time I had the unit I didn't notice any problems.

I'm pleased to report that the machine has an internal mains power supply with an IEC socket fitted at the rear and a front-panel power switch. There is no provision to change the mains voltage, nor externally accessible fuses, and I was surprised at how hot the casing around the power supply area becomes after a short period of use. It certainly was too hot to rest a hand on, although the machine didn't seem to suffer! I would suggest that if the DDP is destined for rackmounting there should be at least 1U of space above and below, to allow air to circulate freely.