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Just ordered; should be in by Monday. These are just starting to become available in the US. I've been looking for something with above average performance but not over $2K, unlike my last two DACs, which while quite satisfactory from a performance perspective, are rather pricey for most of my friends.
ALSO, this new piece from NAD has a number of unique features, including supporting pass through HDMI for two channel audio; this is ideal for my secondary system which is 2.1 for Blu-ray (decodes dual channel PCM), and for digital audio from a Cambridge D100 iPad/iPod interface that outputs S/PDIF and AES/EBU.
Digital processing is done at 35 bits, and includes a remote control volume control, so the unit can act as a digital preamp, like my other two DAC's.
This unit uses the same PCM to PWM class D technology as the NAD M2, reviewed in Stereoophile last year. NAD has collaborated with a British semiconductor company, Diodes Zetex Ltd., which developed a novel feedback topology in which the output pulses are continuously compared with a reference to produce an error signal. This error signal is integrated, digitized (at 108MHz), and fed back, with noiseshaping, to the PWM modulator. The signal is also monitored at the output low-pass filter, to give a low output impedance. The Zetex team refers to their topology as a Direct Digital Feedback Amplifier. In the M51, this is applied at a preamp level instead of power amp level.
In the review of the M2, they noted that the actual measured dynamic range indicated true 20 bit dynamic range at the output, which is the best dynamic range Stereophile has measured. To put that in perspective, that's -140 dB noise floor at ~ 1kHz, decreasing to about -130 dB at 10 kHz. SOTA. All the typical low level tests for DAC's looked very good:
Linearity error with 24-bit data was negligible down to –120BFS, which, in conjunction with the superb resolution, meant that the M2's reproduction of an undithered 16-bit tone at exactly –90.31dBFS was essentially perfect (fig.10). The three DC voltage levels are clearly resolved, with superb waveform symmetry and the Gibbs Phenomenon "ringing" unobscured by noise:
Tested the M2's rejection of word-clock jitter by feeding a 16-bit version of the diagnostic J-Test tone from the soundcard of my test-lab PC via 15' of plastic TosLink. The resulting narrowband spectrum of the amplifier's output is shown in fig.18. The central spike representing the high-level Fs/4 tone shows very little spectral spreading at its base, and the harmonics of the Fs/192 LSB-level squarewave lie at the residual level. Other than the fact that the noise floor in the right channel (red trace) is a little higher than in the left (blue), this is state-of-the-art performance.
NAD M2, line output, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz, 16-bit data. Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz (left channel blue, right red).
If the M51 matches this level of performance, but in a DAC/Preamp, it should set a new value proposition bar at this price point.
Hopefully, it actually sounds good, too. :roll: :W
Here's NAD's blurb about the M51. Something to ponder this holiday when you get tired of egg nog and Christmas carols, and your mind wanders back to music and audio....
I'll be reporting back during the break after I've had a chance to listen to it at some length, and may be find the time to run some tests (have one of the old CBS CD test disks, all the standard waveforms- but no Audio Precision!)
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-Analogue 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.
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 analogue stage with very low output impedance provides the perfect interface to your favourite amplifier. Also, 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 192kHz releasing the previous limitation of USB at 96kHz. Both host and device USB ports are included allowing direct connection of a PC or Mac in addition to the connection of a USB flash or hard disc memory device.
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.
ALSO, this new piece from NAD has a number of unique features, including supporting pass through HDMI for two channel audio; this is ideal for my secondary system which is 2.1 for Blu-ray (decodes dual channel PCM), and for digital audio from a Cambridge D100 iPad/iPod interface that outputs S/PDIF and AES/EBU.
Digital processing is done at 35 bits, and includes a remote control volume control, so the unit can act as a digital preamp, like my other two DAC's.
This unit uses the same PCM to PWM class D technology as the NAD M2, reviewed in Stereoophile last year. NAD has collaborated with a British semiconductor company, Diodes Zetex Ltd., which developed a novel feedback topology in which the output pulses are continuously compared with a reference to produce an error signal. This error signal is integrated, digitized (at 108MHz), and fed back, with noiseshaping, to the PWM modulator. The signal is also monitored at the output low-pass filter, to give a low output impedance. The Zetex team refers to their topology as a Direct Digital Feedback Amplifier. In the M51, this is applied at a preamp level instead of power amp level.
In the review of the M2, they noted that the actual measured dynamic range indicated true 20 bit dynamic range at the output, which is the best dynamic range Stereophile has measured. To put that in perspective, that's -140 dB noise floor at ~ 1kHz, decreasing to about -130 dB at 10 kHz. SOTA. All the typical low level tests for DAC's looked very good:
Linearity error with 24-bit data was negligible down to –120BFS, which, in conjunction with the superb resolution, meant that the M2's reproduction of an undithered 16-bit tone at exactly –90.31dBFS was essentially perfect (fig.10). The three DC voltage levels are clearly resolved, with superb waveform symmetry and the Gibbs Phenomenon "ringing" unobscured by noise:
Tested the M2's rejection of word-clock jitter by feeding a 16-bit version of the diagnostic J-Test tone from the soundcard of my test-lab PC via 15' of plastic TosLink. The resulting narrowband spectrum of the amplifier's output is shown in fig.18. The central spike representing the high-level Fs/4 tone shows very little spectral spreading at its base, and the harmonics of the Fs/192 LSB-level squarewave lie at the residual level. Other than the fact that the noise floor in the right channel (red trace) is a little higher than in the left (blue), this is state-of-the-art performance.
NAD M2, line output, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz, 16-bit data. Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz (left channel blue, right red).
If the M51 matches this level of performance, but in a DAC/Preamp, it should set a new value proposition bar at this price point.
Hopefully, it actually sounds good, too. :roll: :W
Here's NAD's blurb about the M51. Something to ponder this holiday when you get tired of egg nog and Christmas carols, and your mind wanders back to music and audio....
I'll be reporting back during the break after I've had a chance to listen to it at some length, and may be find the time to run some tests (have one of the old CBS CD test disks, all the standard waveforms- but no Audio Precision!)
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-Analogue 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.
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 analogue stage with very low output impedance provides the perfect interface to your favourite amplifier. Also, 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 192kHz releasing the previous limitation of USB at 96kHz. Both host and device USB ports are included allowing direct connection of a PC or Mac in addition to the connection of a USB flash or hard disc memory device.
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.
unk:
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