The NAD C390DD is not only a new concept in amplification, but also in audio system architecture. First introduced in the now famous NAD M2 Direct Digital Amplifier, Direct Digital technology has been praised for its transparent, dynamic and detailed sound quality. Like the M2, the C390DD has no analog stages in the signal path, keeping music in the digital domain right up to the speaker outputs. All preamp functions are executed in the digital domain without the phase shift, noise and distortion that plagues all analog designs regardless of price or pedigree. Its 35 bit architecture and 108MHz master clock also make Direct Digital one of the most accurate DAC technologies available. The C390DD has a very high continuous power rating of 150 watts per channel with almost immeasurable distortion and noise. More importantly, thanks to NAD's exclusive Digital PowerDrive circuit, power delivery into real loudspeakers is enhanced by sensing the speaker load and altering amplifier characteristics to give the most efficient power delivery and best safety margin. This results in power output that can more than triple the rated power for short periods of time to accurately and effortlessly reproduce musical transients. The result is that the C390DD sounds even more powerful than its already impressive continuous power rating.
The Direct Digital platform includes a large amount of DSP processing power, and NAD has fully exploited this power with a toolbox full of useful features. Even familiar features, like the volume control, benefit from the Direct Digital platform. Perfect signal tracking and channel balance combined with a total freedom from noise and distortion characterize this remarkable volume control. Traditional bass and treble controls also take on a new usefulness when distortion and phase shift are totally absent.
An 'electronic crossover' function is also included to easily allow biamplification or subwoofer integration. Frequencies from 40Hz to 200Hz can be selected, with the high pass signal sent to the C390DD amplifier section and the low pass sent to the Preamp Out.
One of the major problems in any high power music system is what we call modes' or 'standing waves'. Because the wave lengths in the bass frequencies are so large, the room dimensions disturb the even propagation of the sound (think of water ripples in a fish tank - when the wave hits the tank boundary a reverse interference wave is produced). The result of this effect is that certain bass notes are reinforced and become much too loud, making the bass sound boomy. This effect actually changes the perception of the harmonic structure of the bass instruments and spoils the illusion of "listening through" to the acoustic space of the recording. Our simple solution is what we call Room EQ. Playing back a supplied test tone sequence allows this problem to be easily tamed using your ears and the C390DD Room EQ filters. There are 6 requency centers in the low bass region that can be cut (or slightly boosted) to remove the 'boom' without reducing the low bass response. The width or "Q" of the filter can also be adjusted to be wide or narrow to address a number of different room configurations.
