Усилители мощности стерео — NAD M28

The M28 is a seven-channel power amplifier from NAD's Masters Series, the Canadian company's high-end line. Announced in August 2020, it replaced the earlier M27 and was the first multichannel amplifier to use Purifi's Eigentakt amplifier technology, which NAD had introduced shortly before in its M33 streaming amplifier. NAD describes it as the most powerful amplifier it has built, intended as the engine of a high-end home cinema or multichannel music system.

Key specs that matter

The M28 delivers at least 200W per channel into 8 ohms and 340W into 4 ohms with all seven channels driven (20Hz to 20kHz), and at least 220W into 8 ohms and 400W into 4 ohms with two channels driven. Dynamic power reaches 560W into 4 ohms, with peaks above 700W into 4 ohms on a single channel. Rated THD is 0.003% or lower from 250mW to rated power. The damping factor exceeds 750. Each channel accepts balanced XLR or single-ended RCA inputs and connects to speakers through binding posts.

Engineering and use context

Eigentakt (self-clocking) is a Class D amplifier design from the Danish company Purifi, built by NAD under licence. It takes into account effects of the output filter inside the feedback loop that earlier Class D designs ignored, and refines the self-oscillating approach NAD used in its previous HybridDigital amplifiers, lowering noise and distortion. Unlike many Class D designs, the M28's frequency response stays wide and even regardless of loudspeaker impedance, and it copes easily with long speaker cable runs, which matters in home cinemas where surround and height speakers are far from the equipment rack. When driven into clipping, Eigentakt recovers quickly and benignly, behaving more like a well-designed Class A/B amplifier than a typical switching amplifier. The efficiency of Class D allows all this power in a compact chassis that runs without the heat and bulk of a linear seven-channel amplifier.

Pairing

The M28 is designed to be driven by a surround processor such as NAD's own M17 V2, or by the pre-outs of an AV receiver for up to seven speaker channels. Balanced XLR inputs suit long cable runs between processor and amplifier, and the high current delivery handles low-impedance front speakers. Two channels can also serve a stereo system alongside the home cinema.

Alternatives

NAD's own M23 is a stereo Masters Series amplifier with Eigentakt technology for two-channel systems.