Power amplifiers stereo — McIntosh MI1250

The McIntosh MI1250 is a digital power amplifier with twelve channels, designed for whole-house audio systems where music is distributed to several rooms at once. It uses closed loop digital switching amplifier modules backed by substantial power supplies and is housed in a 2U rack-mountable case with removable mounting ears, so it can also sit on a shelf outside a rack.

Key specs that matter

Each of the twelve channels delivers 50 W into 8 ohms or 90 W into 4 ohms. Rated total harmonic distortion is 0.05%, and noise is 95 dB below rated output. Frequency response is flat within +0 and -0.5 dB between 20 Hz and 20 kHz. The damping factor is above 65 into 8 ohms and above 32 into 4 ohms. The chassis is 44.45 cm wide, 10.9 cm high and 53.3 cm deep, and it weighs 10 kg. Its heat output is officially rated at 900 BTU per hour, a figure useful when planning ventilation in an equipment rack.

Engineering and use context

Because the Class D output modules run at high efficiency, the MI1250 needs no cooling fans. Power Guard signal overload technology keeps the amplifier from overdriving the speakers, and Sentry Monitor provides short-circuit protection that resets automatically. Multi-color LED indicators on the front panel show the status of each channel. Every channel has its own individual input, and a BUS input and output let one stereo source be spread across many outputs at once, which suits a system where several rooms play the same programme. Signal sensing switches the amplifier on when an input is detected and off again when it goes away, and a 12-volt trigger coordinates its power with other McIntosh components. The front is the black glass panel with an illuminated McIntosh logo seen across the range. McIntosh gives it a 3-year limited warranty.

Pairing

Analogue sources connect through unbalanced RCA inputs, and there are also two digital audio inputs that accept coaxial or optical signals and can be bussed across channels. Speaker cables attach to 2-pole Phoenix style push-in terminals rather than binding posts, a format common in installed multi-room wiring. McIntosh also names the MI1250 among the digital amplifiers intended for distributed audio systems alongside its multichannel home theater models.

Alternatives

The McIntosh MI128 is a smaller digital rack amplifier from the same series, with eight channels of higher output each.