Усилители мощности стерео — McIntosh MI254

The McIntosh MI254 is a four-channel digital amplifier aimed at distributed audio, home theater or stereo setups. It uses closed loop digital switching amplification backed by strong power supplies, and its 2U chassis mounts in a standard rack or, with the mounting ears removed, sits on a shelf. Blue McIntosh Watt Meters on the black glass front panel show the summed power output, framed by an illuminated logo and silver trim.

Key specs that matter

Rated output reaches 250 W per channel into 8 ohms and 300 W per channel into 4 ohms, with an FTC figure of 250 W over a 20 Hz to 20 kHz power band. Total harmonic distortion is listed at 0.025 percent, and S/N is quoted as 100 dB below rated output. Dynamic headroom measures 2.5 dB at 8 ohms and 3.5 dB at 4 ohms. The damping factor is given as more than 85 into 8 ohms and more than 45 into 4 ohms. Frequency response stays within +0 and -0.9 dB from 20 Hz to 20 kHz. The case is 44.45 cm wide, or 48.3 cm with the ears, 11 cm high and 53.3 cm deep, and the unit weighs 10.7 kg, or 18.1 kg packed. The circuit configuration is listed as closed loop digital switching with a direct coupled output stage. Thermal output is rated at 1000 BTU/h.

Engineering and use context

The Class D design needs no cooling fans, which keeps the amplifier free of fan noise in an equipment cabinet. Next to the meters, multi-color LEDs report the state of every channel. Each channel accepts both a balanced and an unbalanced input, giving four balanced inputs in total, while direct coupled outputs lead to standard speaker binding posts. BUS inputs and outputs let a source signal be distributed between channels. Power Guard limits clipping when the input overloads the amplifier, and Sentry Monitor guards against short circuits. Remote power control is supported through a 12-volt trigger, and signal sensing can switch the amplifier on and off on its own for eco-friendly operation.

Pairing

The four channels can serve two stereo pairs of speakers in separate rooms, or the front and surround positions of a home theater driven by a processor with balanced outputs. Its extra output into lower loads allows such speakers to be connected directly.

Alternatives

For two channels, McIntosh offers the MI502 in the same digital line, delivering far more power per channel from a 2U chassis with dual watt meters.