One of our Masters Series’ finest components to date, the M51 Direct Digital™ DAC uses the same high precision digital processing as our ground-breaking M2 Direct Digital Amplifier, but in a new format that easily interfaces with high performance analogue components, including our M22 Stereo Power Amplifier. With features such as extremely low noise, low distortion, wide dynamic range, superb linearity and exceptionally low digital jitter, the M51 will help bring your home theatre system to life. With the ability to accept PCM data rates up to 24 bit/192kHz, the M51 makes it perfect for listening to high resolution downloads, allowing you to hear your favourite songs in the best audio quality possible. Possessing two HDMI inputs and one output with video pass through, the M51 seamlessly becomes the heart of a video 2.0 system, further displaying the M51’s remarkable versatility and innovation.

Digital Innovation
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. Instead of using the Direct Digital™ processor to drive a high power output stage, we employ a line level analogue output that will perfectly interface with any analogue system with the M51 Direct Digital DAC.

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 DACs. Running at 108MHz, the M51 resamples the incoming pulse code modulated (PCM) signal and converts it to a pulse width modulation (PWM) signal 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.

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. Due to the very high clock speed and mathematical precision of our reconstruction filters, the resulting audio signal is totally free of digital artefacts. A Pure Class A analogue stage with very low output impedance provides the perfect interface to your favourite amplifier. Both balanced and single-ended outputs are available.

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 192 kHz releasing the previous limitation of USB at 96 kHz. 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 theatre 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.

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 analogue 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.


  • Rated Distortion (THD+N with AES 17 filter)
  • <0.0005% (0dBFS)
    <0.002% (ref. 1kHz-60dBFS)
  • IMD Distortion
  • 0.0001%
  • Signal/Noise Ratio
  • Channel Separation
  • >-115dB (ref. 0dBFS Volume -1dB)
  • Sample Rate
  • 32kHz to 192kHz (USB and digital S/PDIF)
  • Frequency Response
  • ±0.5dB (ref. 20Hz-96kHz @ 192kHz sample rate)
  • Output Level
  • 2V (ref. input 0dBFS)


  • AES/EBU 
  • SPDIF Coaxial x 1
  • Optical x 1
  • HDMI x 2 (stereo only) 
  • USB Class 2 Audio: asynchronous 24/192 support 
  • IR In
  • Trigger In
  • 12V ±20%


  • HDMI Video Out (3D video pass through)
  • Analogue
  • Unbalanced
  • 47 Ohms
  • Balanced
  • 110 Ohms
  • Trigger Out
  • 12V ±20%


  • AC Supply
  • 100-240V AC ~ 50/60Hz
  • Standby Power
  • <0.5W
  • Idle Power
  • 16W
  • Gross Unit Dimensions* (WxHxD)
  • 435 x 78 x 296mm
    17 1/8 x 3 1/8 x 11 11/16 inches**
  • Net Weight
  • 5.8kg (12.8lb)
  • Shipping Weight
  • 9.8kg (21.6lb)
  • Finish
  • Masters Silver or Black

*Gross dimensions include feet, extended buttons and rear panel terminals

**Non-metric measurements are approximate.



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