- Written by Michael Jude Galvin
- Published on 15 March 2013
Design of the NAD C 390DD Direct Digital Integrated Amplifier
Aside from its Master series, of which the M2 is part and the C 390DD is not, NAD's casework is pretty nondescript—basic shapes in basic black. And so it is with the C 390DD, looking much more mass-market receiver than audiophile centerpiece. Probably because the C 390DD is tall, much taller than a typical integrated amplifier, you notice its aesthetics when it is in your system. It is especially large compared to my reference, the Naim Nait XS-2 integrated amplifier. While not exactly pretty, the NAD's front panel controls are both easy to understand and use and kept to a minimum—a large vacuum fluorescent informational display, volume knob, USB port, and power, source, and navigation buttons. Given the dimensions, the amplifier's 17 pounds are lighter than you might expect, but such is usually the case with digital amplifiers.
Another point of evolution over NAD's own M2 is the C 390DD's modular architecture, which means in addition to the eight digital inputs it has in stock form, it is designed to accommodate expansion cards, which add to its rear-panel connectivity. It features three such rear-panel slots, one of which is filled from the factory by a direct digital USB module, which includes both USB type A and type B inputs. The C 390DD's other rear panel inputs include two coaxial, two optical, and one AES/EBU input. As mentioned above, an additional USB input is located on the front panel. All three USB inputs are asynchronous. The USB type B terminal supports 24/96 resolution, while the type A terminals support up to 24/48.
NAD offers two additional modules (MSRP $300/each) and if you have any analog sources, you will need at least one, the direct digital analog-phono module. The analog-phono module includes balanced and unbalanced line level inputs and perhaps surprisingly, a phono input, which accommodates both MM and MC cartridges. Because the C 390DD operates exclusively in the digital domain, the analog input signals are converted to digital. The line-level analog inputs thus feature user-selectable settings for sample rate (48, 96, or 192 kHz). Of note, the phono input also features an infrasonic filter, which, when activated, filters out frequencies below 10Hz. If you have ever experienced excessive woofer motion that does not correspond to audible sound, you have experienced infrasonic distortion. Such distortion can be caused by a variety of factors, including imperfections in the vinyl, tone arm resonance, and turntable vibration. The other module, the direct digital HDMI module, includes three HDMI inputs and an HDMI output with video pass through. The direct digital HDMI inputs allow the reproduction of the three front channels through the left and right channels in a stereo set-up. The review sample included both the HDMI and Analog-Phono modules. Also of note, the C 390DD includes a stereo preamplifier/subwoofer output.
The C 390DD is fully remote-controlled and its remote can also operate other NAD devices. The remote allows direct access to each of the C 390DD's eight digital inputs and the source selection button allows you to scroll through all the device's inputs. Unused inputs can be deactivated (and thus skipped during input scroll), and all the inputs can be named, which makes the remote interface very user-friendly.