A stunning breakthrough in digital amplifier design
The M2 Direct Digital Amplifier is the product of a decade-long NAD research project that was followed by three years of product development. Highly efficient, immensely powerful and musically involving, the M2 sets a new performance benchmark for digital amplification. It compares favorably with the world's best amplifiers, regardless of price or design philosophy.
"The M2 ... sounds remarkable, with
tremendous dynamics, extremely low noise,
richly textured and defined bass, and three-dimensional soundstaging."
Robert Harley, The Absolute Sound magazine, March 2010
Streamlined signal path dramatically reduces noise
Because the M2 handles digital audio signals directly, you won't hear the noise and distortion that's added by the analog amplifying stages found in traditional amplifiers. NAD says this streamlined signal path reduces overall system noise by a factor of three.
Without all that noise to compete with, the subtle details you never noticed emerge from music you've heard a hundred times. You perceive the dimensions of the performance space and the rich tonal texture of each instrument. What once sounded like a mere violin now reveals itself as a Stradivarius, and you savor each note as it blossoms and ripens before yielding to the next one.
Typical signal path through an analog system
The diagram at right shows the signal path of a traditional amplifier setup, which includes as many as 10 steps between the digital audio source and your speakers, including:
The digital-to-analog converter and its buffering circuitry. If it's a stand-alone converter, there will be a cable from there to the preamp.
The analog preamp and its buffering circuits. If it's a separate unit, then add one more cable to the signal path.
The analog power amplifier, which typically places three more stages of circuitry in front of the output stage.
M2 signal path
The diagram below shows the path the signal from a digital music source takes through the M2 on its way to your speakers. The only stop along the way is to decode the signal. You can think of the M2 as a DAC with a built-in amp. It's that simple, and that's why noise and distortion vanish.
Groundbreaking Zetex chip cancels out distortion
The Zetex DDFA (direct digital feedback
amplifier) chip enables NAD's breakthrough in class D amplifier sound quality. Until now class D amplifiers had been used primarily in subwoofer amps, because their full-range sound could not compete with the sound of the best analog amps.
The other thing that makes the M2 unique among class D amps is the use of feedback to minimize distortion in the output stage. If you've ever tried a pair of noise-canceling headphones, then you have a good idea how feedback works: a microphone on the outside of the headphone picks up the noise, and built-in circuitry mixes in a mirror image of the noise to cancel it out.
Feedback systems in amplifiers don't use microphones, but the concept is the same. The output signal is compared with the input signal, and a mirror image of the difference (distortion) is introduced in order to cancel it out. This technique has been used for years in conventional amps, but has been impractical in class D amps until now. NAD collaborated with a company called Diodes Zetex on a breakthrough technology called DDFA (direct digital feedback amplifier) for the M2.
DDFA requires an extremely robust processor in order to feed the inverted error data back fast enough. If you comprehend such things, the Zetek chip operates at a 108MHz sample rate on a 35-bit-wide data path. The M2 is the first, and for now the only, vehicle on this superhighway.
Advanced power supplies
Class D amplifiers require hefty and exceptionally quiet power supplies. These parts are large, heavy and costly, but they are absolutely essential. The M2 uses three very substantial and highly efficient power supplies, one for each channel and a third for the input stage and control sections.
Excellent performance under the most demanding conditions
Digital PowerDrive helps the M2 maintain the lowest possible distortion and deliver breathtaking dynamics, even when driving difficult speaker loads.
Digital Soft Clipping is a new take on a technology NAD pioneered in the 1970s. In the unlikely event that you overdrive the M2, this circuit prevents the harsh sound and potential speaker damage that can result when the overdriven amplifier clips the tops and bottoms of the music signal's waveform.
Multi-stage fail-safe protection prevents amplifier or speaker damage. Short circuit, DC offset, overheat, and over current faults are handled instantly and an indication of the fault is displayed on the front panel.