The M51 DAC is made with the company's inherent solidity and extensive functionality. Despite the slim body, the device has a massive front panel made of aluminum. It is extremely laconic - power switch, display and input selection button. The remote control is included.

The M51 is not only suitable for work as a stereo DAC, but also perfectly prepared for integration into a theater system. In addition to the main inputs, it has a balanced digital AES/EBU and a pair of HDMI inputs that can be fed from a turntable or satellite receiver. However, in all cases we are not talking about multichannel sound - you can get only classic stereo signal from analog outputs. But there is a HDMI-through output. And here there are no restrictions on signal formats, even 3D video is supported.

The most interesting part of the M51 is the path. For all inputs it is possible to process data with sampling rates from 32 to 192 kHz (USB by Audio Class 2.0 asynchronous transmission specification). The digital stream after reception is resampled by a 108 megahertz processor and converted to a PWM signal with 844 kHz subcarrier. Digital volume control is also available and is performed with virtually lossless quality by a 35-bit DSP. Thus, NAD implemented the concept of Direct Digital Technology in its converter. To put it simply, with the M51 such a component as a preamplifier is completely eliminated if the system is not intended to have purely analog sources. The unbalanced or balanced outputs can be sent directly to the power amplifier.

Admittedly, the M51 intrigued me the most. Unusual path, excellent performance, very attractive price. And the first use, indeed, had a stunning effect. This converter sounded very rich, detailed and powerful. The timbres were beautifully laid out, the dynamics seemed unconstrained, and the scene, albeit a bit blurry in the plans, was very, very deep. And from a formal position everything seems to be fine - no noticeable coloration, clean top, detailed and fast bass. I thought that M51 may well become the component "cure", which is able to radically improve the sound of already familiar stereo system. After all, NAD refined the musical balance, revealed some new harmonic shades and details. But the question is whether they were in the source? There is no exact answer. And the more I listened to it, the more the feeling of synthetic sound grew.

When I switched to USB something changed. The playback became more neutral, the microdynamic elaboration improved. The sound now aroused more confidence, but the "magic" of the added harmonicity manifested itself here as well - instead of a true and sometimes not the most pretentious musical picture this converter offered its chic stage interpretation.

The timbres are beautifully laid out, the dynamics seem to be unconstrained, and the scene, even if a little blurred in the plans, is very deep.

NAD M51 DAC photo