"Sweetly Balanced" DAC Performance
NAD's revolutionary new M51 Digital-to-Analog Converter is the first to incorporate NAD’s Direct Digital technology, which first captured the attention of serious music lovers in the Masters Series M2 Direct Digital Amplifier. Just as the M2 helped to redefine the power amplifier, the M51 includes an astonishingly powerful digital engine that sets a new benchmark for DAC performance.
"The M51 sounds meaty and powerful in the bass, warm and almost 'tubey' through the midband, and sweetly balanced at the top end: making for a relaxed sonic presentation that's particularly forgiving of harsher recordings and rarely grates," raves a May 22, 2012 review in Hi-Fi News and Record Review.
"Completly neutral, but nevertheless very relevant presentation , spacious, detailed, fast dynamic, musical audiophile...how many boxes should I check?" asks HiFidelity magazine from the Netherlands.
Digital Processing Firepower
You've never seen digital processing firepower like this before. The M51 is a 35-bit, 844 kHz DAC that supports the newest USB codec for 24-bit 192 kHz audio transmission. Upsampling to 35-bit, 844 kHz delivers a level of presence and realism to digital audio files unlike anything that you have previously experienced. Performance is absolutely breathtaking, as befits a 'Masters Series' component.
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 66 dB (very, very quiet) before bit truncation begins.
Pure Performance
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; again, offering state-of-the-art performance in this most important parameter. Due to the very high clock speed and mathematical precision of our 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.
More than Just a DAC
The 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 digital format. All this innovation, performance and flexibility come with NAD's legendary sound quality and affordability.
The Masters Digital Suite
The M51 is an integral part of NAD's new Masters Digital Suite, which includes the M2 Direct Digital Amplifier, M50 Digital Music Player, and M52 Digital Music Vault. Like all Masters Series products, the M51 DAC represents the best in NAD innovation and performance and heralds a bold new architecture for high-end digital audio systems.
Advanced Digital Volume Control
The NAD M51 can act as a complete digital preamp thanks to multiple inputs and its 'perfect DSP volume control.' This high-resolution digital volume control has an astoundingly high attenuation range and perfect channel balance. Unlike most digital volume controls, this sophisticated circuitry does not truncate bits. You'll swear you're listening to a smooth, ultra-quiet analog section.
The preamp functionality allows you to connect the M51 directly to a high-quality amplifier without the need for a separate dedicated preamplifier.
Connection Heaven
The M51 provides a wide array of digital inputs, allowing you to connect a system's worth of components. The SPDIF inputs include AES/EBU, coaxial, and optical. Also onboard are two USB inputs (1 host, 1 device). It also supports HDMI digital audio, providing two HDMI inputs (stereo only, no surround decoding) and an HDMI output with 3D video pass-through. On the analog side, the M51 offers both RCA single-ended and XLR balanced stereo outputs.
Inputs can be named for an added touch of convenience, and the front-panel VFD display shows input, sample rate, and volume level. For system integration and custom installations, the M51 also includes an RS-232 interface for external control, a 12-volt 'trigger' in, and an IR in. An infrared remote control is included.
The Greening of NAD
Last but far from least, the M51 is a 'Green' design that uses less than <0.5W of power consumption in standby mode.
NAD takes its responsibilities to the planet very seriously by pursuing forward-thinking, environmentally aware manufacturing. The company imposes strict measures in all its product designs to eliminate environmentally hazardous materials and minimize power consumption. It uses lead free solder throughout manufacturing, and has re-designed its circuit board production to eliminate environmentally dangerous chemical compounds. | 
