Stereo master amplifier4/20/2023 20Hz-20kHz (250mW to rated power), with a damping factor of >750 (ref. The M28’s specified total harmonic distortion (THD) is ≤0.003% ref. Judging by the specs provided by NAD, the M28 can do this. An amp’s ability to direct more power dynamically to one or a few channels is often more revealing of what it can actually do. Outputting large amounts of continuous power through all channels is difficult and impressive, but is rarely required in real-world situations. While NAD seems to specify their amplifiers more conservatively than do many other manufacturers, the M28’s output specs are still open to interpretation-therein lies the rub with multichannel amplifiers. Of course, manufacturers’ power-output specs don’t always indicate an amp’s actual performance. The specified IHF dynamic power into 8 ohms is 280Wpc, all channels driven, or 560W, one channel driven. rated THD, 20Hz-20kHz, all channels driven. The M28’s specs indicate a bump in power: 200Wpc into 8 ohms or 340Wpc into 4 ohms, both ref. The M27 was specified as outputting 180Wpc of continuous power and 300W of peak power into 8- or 4-ohm loads, all channels driven. The M28 also has a complex active power supply claimed to act more like a power amp that outputs DC, and to maintain the correct output voltage over a wider range of input voltages than a linear power supply. Because the Eigentakt amp is low in gain, NAD adds a gain stage to bring it up to 28dB to ensure better compatibility with other components. This allows them to ensure that the quality of each module is at least as good as the reference, to maintain the M28’s overall performance. As they do for their Masters M33 integrated amplifier-DAC, NAD builds the Eigentakt amp modules themselves, under license from Purifi. The M27 and the M28 may look identical the key difference between them is that the M28’s Purifi Eigentakt amp modules replace the M27’s Hypex Ncore amps. This last button can also be held down until that front light flashes, to toggle the M28 between normal operation and Auto, which puts it into Standby mode after 30 minutes of receiving no source signal. A small toggle switch selects between each channel’s single-ended and balanced inputs.Īlso on the rear panel are a three-bladed IEC power socket for the provided cord, a rocker switch for mains power, a fuse bay, an LED for each channel indicating Normal or Fault status, a 12V trigger input, and an LED level button for dimming or darkening altogether the front-panel power indicator. Each channel’s inputs and outputs are neatly and vertically aligned, the former above the latter. The M28 retains the same input and output connections as the M27: for each of its seven channels, a single-ended (RCA) and a balanced (XLR) input, and a pair of high-quality speaker binding posts. The light surrounding the NAD logo on the left of the front panel glows amber in Standby, white for On, and red to indicate a short circuit. This takes a little getting used to-the button provides no tactile feedback, and after it’s touched, there’s a slight delay before the M28 powers up. The M28 is warranted for two years for parts and labor-not all that long for a product for which its manufacturer clearly has high-end aspirations.Ī capacitive-touch button at the front of the top panel selects between Standby and On. The M28 and M27 have identical dimensions of 17.1″W x 6.2″H x 15″D, but at 33 pounds the M28 outweighs its predecessor by two pounds. The M28’s spiked feet can be set on magnetized discs (provided) to keep the spikes from scratching the surface the amp is placed on. The black top and front panels provide a nice contrast to the thick, brushed aluminum of the rest of the M28’s case-seven years on, the result is still a handsome, modern-looking amp. They have the same black top panel with 12 large, square, grilled vents. To the eye, there’s little difference between the Masters M28 and the earlier Masters M27 ($3999, discontinued), which I reviewed in April 2014-except for the “M28” screened onto the top of the black front panel, they’re outwardly identical. The subject of this review is NAD’s Masters M28 multichannel power amplifier ($4999, all prices USD), which boasts seven channels of Purifi Eigentakt technology. Those class-D amp modules provide high power with extremely low distortion and, most important, extremely neutral and musically satisfying sound-as I discovered in September 2020, when I reviewed NAD’s Masters M33 integrated amplifier-DAC, which is based on the Eigentakt amp. If you’re a regular reader of the SoundStage! Network websites, you know that we, and especially our founder and publisher, Doug Schneider, are big fans of Purifi Audio’s Eigentakt amplifier technology. Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.
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