McIntosh MI128 - Black

Description

8 Versatile Digital Channels in a 2U Rackmount Chassis

The McIntosh MI128 is an 8-channel digital amplifier in a 2U rackmount form factor — the ideal balance between channel density and per-channel power in the McIntosh Custom Install lineup. Unlike the MI1250 (12 channels at 50 W, focused on maximum zone density), the MI128 offers 8 channels at 120 W per channel — 2.4× more power per channel — which makes it much more versatile. Typical applications: multi-zone distributed audio (up to 4 stereo zones — kitchen, living room, primary bedroom, patio), a 5.1 or 7.1 home theater system driven by a single amplifier, or a bi-amped stereo installation (one channel pair per frequency section of a multi-way loudspeaker). Rack-mount ears are included (and removable for non-rack installations).

Closed-Loop Digital Class D Amplification: 120 W / 150 W Per Channel

Each channel of the MI128 uses a closed loop digital switching amplifier module paired with a robust power supply — a modern, highly efficient Class D design that delivers 120 W per channel into 8 ohms and 150 W per channel into 4 ohms. The sophistication of the closed loop and the power supply yields performance levels across the 8 channels rarely achieved in distributed audio. The high efficiency of Class D means the MI128 does not require cooling fans: fully silent operation, which particularly matters in a domestic environment where the amplifier is often installed in an equipment rack near living areas. 0.05% THD, 95 dB S/N below rated output, dynamic headroom 2.1 dB (8 Ω) / 3.3 dB (4 Ω), damping factor >65 (8 Ω) and >32 (4 Ω), frequency response +0/-0.5 dB from 20 Hz to 20 kHz. Direct Coupled output.

Rear Panel: Per-Channel RCA + Bussable Digital Inputs

The MI128's rear panel offers one unbalanced RCA input and one 2-pole Phoenix push-in speaker terminal per channel. The removable Phoenix terminals are particularly convenient for professional installation: the integrator prepares and screws the speaker cables into the terminals ahead of time, then simply clips each terminal onto the matching channel on the rear panel. In addition to the 8 individual RCA inputs, the MI128 accepts two bussable digital audio inputs — either coax or optical — that can feed multiple channels simultaneously. Each channel also has an individual rear-panel volume control to balance level between speakers of different sensitivity or between listening zones.

BUS Input/Output and Channel Summing for Distribution

The MI128 provides several mechanisms for distributing a source signal to multiple channels or multiple amplifiers. BUS inputs and outputs: easily distribute a single stereo signal across multiple channels of the same MI128, or across multiple chained McIntosh amplifiers (a MI128 + a MI1250 for 20 channels, for example). Channel summing circuits: convert a stereo signal into a mono signal for distribution to mono speakers (typical for background zones where the available source is mono). The bussable digital inputs let you distribute a digital source (network streamer, CD transport) to multiple MI128 channels without going through intermediate analog conversion.

Power Guard®, Sentry Monitor™, and Auto On/Off Protection

The MI128 carries the McIntosh proprietary protection technologies. Power Guard® continuously monitors the input signal and adjusts gain in real time to prevent clipping — critical protection for the tweeters of in-wall, in-ceiling, and outdoor speakers, which are particularly sensitive to clipping. Sentry Monitor™ is a fuseless short-circuit protection circuit: it disengages the output stage before current exceeds safe operating levels, then automatically resets as soon as conditions return to normal — no fuse in the signal path, no manual intervention required. Eco-friendly signal-sensing auto on/off: the MI128 turns off automatically after a period without an input signal, and turns back on automatically when a signal appears on the input. 12V Trigger input and output ports to synchronize its power state with a preamplifier, an AV processor, or a third-party home automation controller.

Three Applications: Distributed Audio, Home Theater, Bi-Amped Stereo

The MI128's versatility comes from a good balance between channel count and per-channel power. Application 1 — multi-zone distributed audio: a single MI128 drives up to 4 discrete stereo zones (8 channels ÷ 2 = 4 zones) — kitchen, living room, primary bedroom, patio for example. 120 W per channel is plenty for demanding in-wall or outdoor speakers. Application 2 — home theater: 8 channels cover a 5.1 or 7.1 layout with spare channels to drive a secondary zone amplifier. Application 3 — bi-amped or tri-amped stereo: each channel pair drives a separate frequency section of a multi-way loudspeaker (one pair for bass, one for mids, one for highs).

Common Questions

Is the MI128 a distributed-audio or a home-theater amplifier?

Both — and for bi-amped stereo listening as well. That versatility is what makes the MI128 stand out in the Custom Install lineup: its 8 channels at 120 W per channel can drive up to 4 discrete stereo zones in distributed audio (kitchen, living room, bedroom, patio), OR cover a 5.1 or 7.1 home theater configuration, OR drive the separate frequency sections of a bi-amped or tri-amped loudspeaker. For a project focused on maximum zone density rather than per-channel power, the MI1250 (12 channels at 50 W) is a better fit. For a project focused on maximum per-channel power (very demanding speakers), the MI502 (2 channels at 500 W) is a better fit.

How do the MI128's bussable inputs work?

The MI128 has 8 individual RCA inputs (one per channel) AND two bussable digital audio inputs (coax or optical, your choice) that can feed multiple channels at once. The principle: rather than sending a source to a single channel, the bussable inputs distribute the signal to a group of channels — for example, distributing a streamer's digital output to the 4 channels of a living room + kitchen zone, with no external preamplifier or router in between. The MI128 also has dedicated BUS input and output ports that distribute a stereo signal to multiple chained amplifiers — a MI128 (8 channels) + a MI1250 (12 channels) for a 20-channel system sharing a common source, for example.

Can the MI128's channels be bridged?

No, the MI128's channels are not bridgeable (Mono Bridge: N/A). If more per-channel power is required, the Custom Install range offers alternatives: the MI254 (4 channels at 250 W into 8 Ω) offers more power in the 2U format with fewer channels; the MI502 (2 channels at 500 W into 8 Ω, 800 W into 4 Ω) is the most powerful per channel in the Custom Install series. Each of those amplifiers can also be combined with the MI128 in the same equipment rack via the BUS in/out to build a hybrid custom system.

What's in the Box

McIntosh MI128 8-Channel Power Amplifier

Rack-mount ears (removable) and mounting hardware

2-pole Phoenix push-in speaker terminals

AC power cord

Owner's manual