The Award-Winning NAD M51 is a 35-bit/844kHz Reference DAC and Digital Preamp
NAD's Direct Digital technology is unique in both its extreme precision
and in its speed. This advancement was first introduced in the NAD M2
Direct Digital Amplifier to worldwide acclaim. Now this innovative
Direct Digital technology is available as a standalone DAC in the M51 Direct Digital DAC.
Instead of using the Direct Digital processor to drive a high power
output stage, M51 employs a line level analog output that will perfectly
interface with any analog system.
"I'm truly amazed at the performance of this $2,000 DAC. It is
state-of-the-art in design, but more importantly, also in performance.
Its unique HDMI input, which displayed incredibly low distortion, makes
this product a must-consider if you are thinking about purchasing an
– John E. Johnson, Jr., Secrets of Home Theater and High Fidelity
How Direct Digital Operates
NAD's technology uses a very powerful processing engine that operates at
much higher speed and with much greater accuracy than typical
Digital-to-analog converters. Running at 108MHz, the M51 resamples the
incoming pulse code modulated (PCM) signal and converts it to a pulse
width modulation signal (PWM) with a sampling rate of 844kHz. Operating
in a differential mode with double precision, the M51 has
state-of-the-art specifications for low noise and freedom from
distortion. The extreme headroom afforded by the 35-bit architecture
allows for a DSP-based volume control that does not reduce resolution.
Even with 24-bit high definition signals, the output can be attenuated
by 66dB (very, very quiet) before bit truncation begins.
"NAD effortlessly captures the silky shine of the violin, a sound
not unlike a really fine wine - full of complexity and tonal depth,
rounded and smooth with no brittleness to it. For its ability to beguile
and seduce tonally, and in particular its ability to capture the human
voice, it is well worth an audition."
– Rafael Todes, HiFi World
The incredible precision of the M51's processing engine gives music a
vibrancy and transient accuracy that must be heard to be appreciated.
The conversion process from PCM to PWM completely eliminates any jitter
present on the incoming signal. Due to the very high clock speed and
mathematical precision of the reconstruction filters, the resulting
audio signal is totally free of digital artifacts like ringing. A Pure
Class A analog stage with very low output impedance provides the perfect
interface to your favorite amplifier. Also, both balanced and
single-ended outputs are available.
"The NAD M51 succeeds with a wonderfully detailed and revealing
sound best described as honest, with a friendly smile. And it was a
pleasure to listen to."
– Jon Iverson, Stereophile
Next Generation Connectivity
While the M51 includes the industry standard SPDIF, AES/EBU, Optical and
Coaxial inputs, it also includes the latest USB technology called USB
Audio Class 2. USB Audio Class 2 supports sample rates of 192kHz
releasing the previous limitation of USB at 96kHz. A device USB port is
included allowing direct connection of a PC or Mac.
The M51 offers two HDMI inputs and one output with video pass
through. This opens up the possibility of using the M51 Direct Digital
DAC as the heart of a "Video 2.0" system using the mandatory two-channel
linear PCM soundtrack from Blu-ray or DVD to make a compelling
two-channel high definition theater presentation. Many symphony
orchestras and some specialty music labels are also released in HD
recordings on Blu-ray or DVD. The M51 is fully 3D video compatible but
there is no surround sound decoding or video processing.
"The M51 sounds sensational. In fact, we'd go further than that
by saying it's one of the best NAD separates we've heard in recent
– What HiFi?
More than Just a DAC
M51 is a fully functional digital preamp with seven digital
inputs and one of the world's best volume controls. As a 'preamp' it is
totally noise and distortion free because all switching and volume
control is done in the digital domain. There are no analog circuits
except for the Class A buffer at the output of the DAC. While input
selection is available from a front panel control, volume can only be
selected via remote control. The supplied IR remote also features
controls for NAD's matching M50 Digital Music Player. Serial control is
available via RS-232 IR and 12V trigger inputs allow the M51 to fully
integrate with advanced automation systems.
The M51 introduces many 'firsts' for the DAC product category: first to
support HDMI, first to support USB Audio Class 2 with support for
192kHz, the first to use digital error correction, and the first 35-bit
architecture to be found in a DAC. Whether you want to get into computer
audio, 'Home Cinema 2.0' or just want to upgrade your CD player, the
M51 Direct Digital DAC will get the best possible performance from every