In the "stereotype" of most enthusiasts, in the face of European and American equipment, they always subconsciously label themselves with valuable labels, but there is such a European and American brand that is recognized by everyone with "affordable" and "cost-effective" and other people-friendly labels, that is, British NAD. Founded in 1972, NAD has been developing for many years, and has made achievements in the field of Hi-Fi and home theater. I think one of NAD's biggest achievements is to break the user's disapproval of Class D amplifiers, it turns out that Class D amplifiers can also sound so good, and M28 is such a product.
Class D amplifiers also have springThe M28 is a seven-channel back-amp amplifier with a power rating of 200W (8 ohms) per channel, which is said to be a conservative statistic, and can even reach a dynamic peak of 320W. It can reach 700W under the load of 4 ohms, and in the frequency response range of 20Hz-20kHz, the total harmonic distortion is less than 0003%, and the dynamic range can easily exceed 100db. The M28's ability to easily push multiple loudspeakers to high sound pressure is derived from the Purifi EigneTakt Class D amplifiers that NAD has on board. When it comes to Class D amplifiers, they often make audiophiles "scoff", which is also a stereotype, thinking that Class D amplifiers have unpleasant sound, high distortion, insufficient detail and other shortcomings. With the rapid development of chip technology and the increasing perfection of power tubes, Class D amplifiers have gradually become a popular integrated solution. NAD is the leader in the use of Class D amplifiers, and the M28 uses the 1ET400A Class D amplifier module produced by Purifi Audio. 
Tough 1ET400AThis 1ET400A Class D amplifier also has its amazing features, the 1ET400A is a 400W single channel, which can do THD+N:<000017% (+116dB) 100W, 4, 20-20kHz, which can almost be called crazy Class D amplifier. Of course, this is inseparable from Purifi's Eigentakt technology, which has been studied for a long time in nonlinear control theory and produced oscillation amplifier control, which has made the feedback of Class D amplifiers qualitatively optimized. The EIGENTAKT technology uses the same load, volume and signal parameters on the loudspeaker, resulting in negligible THD and IMD levels and very clean clipping characteristics. In 2019, NAD announced that it had become the first international audio brand to adopt Purifi's new Class D technology at the Munich Audio Exhibition in Germany, and launched the then flagship class ** power amplifier M33 the following year, one of the selling points was the use of 1ET400A Class D power amplifier, which shows how important the Class D power amplifier designed and produced by Purifi is. For users who have used the M28, almost unanimously praised, the M28 has a strong driving force, an open sound field, and can handle large dynamic scenes well, even at high volume, the sound is still delicate and clean. 
Thoughtful modular designNAD's modularity has been said too many times, but every time I encounter it, I can't help but praise it, and this forward-thinking design makes it easy to enjoy the latest audio technology on a low budget, and it is convenient for users to update and upgrade the system. M28 also adopts modular design, the machine is equipped with 7 power amplifiers, each channel has an independent power amplifier responsible for driving, so the power output required by M28 is quite strong, M28 uses switching power supply in power supply, and supplies power to 7 power amplifiers at the same time, the power supply adopts 15A 250V specification, which can provide a maximum power of 3750W. The exterior of the M28 is minimalist, with a large black panel with a silver bezel and a glowing NAD logo that acts as an indicator light, white during normal operation, amber when standby, and red when short-circuited, and the working status is clear at a glance. At the top of the fuselage is NAD's traditional square vent for heat dissipation while the machine is running. In terms of backplane interface, the M28 is equipped with 7 RCA inputs, 7 corresponding balanced XLR inputs, and provides a toggle switch to easily switch between the two input modes. Each of the seven channels is equipped with a pair of gold-plated binding posts that can accommodate 4mm banana plugs and oversized speaker cables. 
SummaryNowadays, there are many brands on the market that use Class D amplifiers, and it is not uncommon for multi-channel amplifiers to use Class D amplifiers, but there are very few brands that can be widely recognized by users, and NAD is one of them. In addition to the powerful 1ET400A Class D power amplifier, the technical adjustment of NAD cannot be ignored. M28 is so "stacked" in terms of configuration, only to obtain high-quality sound performance, while not forgetting to bring users high-cost product benefits. Basic technical parametersNumber of channels: Seven channel output output power: 200W (8 ohms, 20Hz-20KHZ, when two channels are driven) Frequency response: 20Hz-20KHZ (0..)1dB) Input interface: RCA, XLR signal-to-noise ratio: 124dB (A-weighted, balanced dB (A-weighted, single-ended) Total Harmonic Distortion + Noise: 0003% (20Hz-20kHz) Damping Factor: 750dBSize (Hw D): 156 435 380mm Weight: 212kg