Integrated Amplifiers

NAD D 3020 Hybrid Digital Stereo Amplifier


The Design of the NAD D 3020 Hybrid Digital Amplifier

My first impression is that the D 3020 is a very stylish piece of gear which will fit right in with office or living room décor. It's fairly small in size; about as a large as a hardcover book. The front and top have a flowing fascia of shiny black plastic that is interrupted only by a volume knob and a headphone jack. The sides are flat black with a slightly rubbery feel. At the top are touch-sensitive buttons for power and source toggle. Included in the box are four stick-on feet.

You can lay the unit on its side if you wish but then you'll be forced to look sideways at the front panel display. It's arranged in two columns; the left indicates the source and right indicates the volume level. On first glance, increments of 20 dB seem pretty coarse compared to a computer-style bar graph. In operation however, the individual numbers change in brightness to convey a little more information. The volume knob controls an extremely precise attenuator. And its feel is very high quality with just the right level of smooth resistance.

Around back is a complete set of inputs and outputs. Starting from the left, we have a 12v trigger input which can be connected to your source device so the D 3020 comes on with a single button press. Above that is a tiny BassEQ button. Toggling this on will provide a 6 dB boost at 80 Hz. Then there is an input cluster consisting of asynchronous USB, RCA, 1/8" mini-plug (which doubles as an optical input via an included adapter), digital coax, and TOSLink. Speaker outputs are the same beefy 5-way binding posts you'd find on full-size receiver or amplifier. There is also a subwoofer output in the form of a 1/8" mini-plug, which is a bit unusual. Rounding out the back panel is a jack for the detachable power cord.

The remote is fairly minimal in nature. The only buttons are on/off, volume, play/pause, forward/reverse, and source next/previous. It works just fine within a wide range of angles when pointed at the D 3020. My only complaint is its black on black design. The button icons are molded in without any sort of contrasting color. It's difficult to see what the buttons do in anything but bright light. And they are not raised at all so you can't operate the remote by feel. It's a little odd but at least you'll be using only the volume control most of the time. I did like the rubberized finish on the front but the back panel is a shiny piano black that becomes instantly covered with fingerprints. It also has a wide enough base that you can stand it on end if you want.

NAD has packed some terrifically innovative technology into this tiny box. As you'll see later in my listening impressions, size does not indicate strength here. This is more than a mere desktop amplifier. It is fully capable of anchoring a two-channel system with large full-range speakers; and driving it to extremely high volume levels with vanishingly low distortion. While it is based on the M2 Direct Digital amp, it doesn't actually do all its processing in the digital domain like that $6,000 component. Analog Class D amps are employed along with a super-simple preamp section. Eight Cirrus anchor the DAC section, mixed down to two channels.

The amplifier section is not your typical Class D module. It's called UcD and is a unique patent licensed from the Dutch company Hypex. It is optimized for high current and low impedance; which explains its ability to drive four ohm speakers with ease. NAD adds in its own refinements to the Hypex technology. One example is PowerDrive which throttles power supply output based on actual load. This leaves plenty of headroom when a quick spike in volume demands greater voltage. This also accounts for its high efficiency and low heat output.

Here are the UcD amp's chief benefits, as highlighted in a white paper I obtained from NAD:

  • Load invariance, meaning it doesn't change sound with different speaker impedances
  • Unaffected by very low impedances
  • Loop gain is constant over the full audio frequency range leading to low distortion even at high frequencies
  • Ability to be constructed with all discrete parts (no expensive control ICs)
  • Excellent EMC (electro-magnetic compatibility) performance
  • Low, flat output impedance for good bass control
  • Flat response in all loads
  • Distortion that is extremely low even into low impedance at the highest frequencies

As you'll see later in my listening comments, I heard clear examples of all these things.