McIntosh · Custom Install Power Amplifier

McIntosh MI347 Power Amplifier

$6,500

Signature technologiesThe McIntosh story

On demonstration in our Portland showroom

McIntosh · Custom Install Power Amplifier

The MI347 is a seven-channel Class D theater amplifier that weights its power the way a room uses it: 250 watts to each of the three front channels and 125 watts to the four surrounds, in a 3U rack chassis of 32.5 pounds.

Class D, 3U rack mount with removable ears. Three-year limited warranty.

3 × 250 W
front channels into 8 Ω; 300 W into 4 Ω
4 × 125 W
surround channels into 8 Ω; 200 W into 4 Ω
3U
6 1/16 in high; 19 in wide with ears
32.5 lb
14.8 kg; 1,500 BTU/h heat output

Authorized McIntosh Labs dealer · Delivery and installation by Pearl Audio · Trade-ins welcome

The story

Most seven-channel amplifiers give every channel the same power, which means the surround channels, which rarely see more than a fraction of what the front three carry, are paying for headroom they will not use. The MI347 is built the other way. Its three front channels are rated at 250 watts into 8 ohms and 300 into 4; its four surround channels at 125 watts into 8 ohms and 200 into 4. All seven are closed-loop Class D with 2.5 dB of dynamic headroom at 8 ohms and 3.5 at 4, distortion of 0.025 percent and a damping factor above 85, and the whole amplifier is 6 1/16 inches tall, 32.5 pounds, and cooled by convection through its top and side vents.

Every channel has a balanced and an unbalanced input and a pair of standard five-way binding posts, so the MI347 connects to a processor with one set of balanced cables and to loudspeakers with ordinary spades or bananas. Power Guard trims each channel's input before it can clip, Sentry Monitor shuts a channel's output stage down on a short circuit and resets itself, and signal sensing turns the amplifier on when the processor sends audio and off after a quiet period; Power Control does the same from a McIntosh processor's trigger. There are no meters, which keeps the 3U height, but a multicolor LED per channel on the glass panel shows status at a glance. The rack ears come off for a shelf in a cabinet.

McIntosh designed the MI347 around its MX-series processors, and in a Pearl Audio theater it sits under the MX200 or MX124 as the complete amplification for a 7.1 room. For Dolby Atmos or DTS:X layouts with height channels, an MI254 adds four more at 250 watts and an MI128 adds eight at 120, all in the same rack format and powered through the MIP200 controller with its sequenced start-up.

The MI347 is the practical foundation for a McIntosh theater in a rack or a closet. The MC257 is the linear alternative, with 200 watts to every channel, a TripleView meter and 95 pounds of chassis, at twice the price; the MC303 gives a front stage 300 watts through Autoformers and leaves the surrounds to a second amplifier. Which is right depends on whether the amplifier will be seen, how far the loudspeakers are from the rack, and how much of the budget belongs to the front three channels.

McIntosh MI347 MX100,  System Lifestyle

Key technologies

  • Closed-loop Class D. Switching output stages with feedback taken after the output filter, so the loudspeaker's impedance has little effect on frequency response, fed by power supplies sized for the rated output; efficiency is high enough that no fan is needed.
  • Power Guard. Monitors each channel for the onset of overload and trims the input before the output clips, so loudspeakers are never driven with a flattened waveform.
  • Sentry Monitor. Fuseless short-circuit protection that disengages the output stage before current becomes unsafe and resets automatically when the fault clears.
  • Signal sensing and 12 V trigger. The amplifier switches itself off after a set period without input and back on when a signal arrives; a 12 V trigger and McIntosh Power Control tie it to a processor or control system.
  • Weighted channel power. 250 watts to the three front channels and 125 watts to the four surrounds, into 8 ohms, so the budget and the headroom go where a soundtrack puts the demand.
  • Balanced and unbalanced inputs on all seven channels. A processor's balanced outputs connect directly, with RCA inputs available for sources that lack XLR.
  • Convection cooling in 3U. Top and side vents dissipate 1,500 BTU/h without a fan; the removable ears fit a 19-inch rack or come off for a cabinet shelf.
Specifications
Type Seven-channel Class D power amplifier, closed-loop digital switching, direct coupled
Power output Front three channels: 250 W into 8 Ω, 300 W into 4 Ω. Surround four channels: 125 W into 8 Ω, 200 W into 4 Ω
Rated power band 20 Hz – 20 kHz
Total harmonic distortion 0.025%
Signal-to-noise ratio 100 dB below rated output
Dynamic headroom 2.5 dB into 8 Ω; 3.5 dB into 4 Ω
Damping factor Greater than 85 into 8 Ω; greater than 45 into 4 Ω
Frequency response 20 Hz – 20 kHz, +0/−0.9 dB
Inputs 7 balanced (XLR), 7 unbalanced (RCA)
Speaker terminals Standard five-way binding posts, one pair per channel
Meters None; multicolor status LED per channel
Protection Power Guard, Sentry Monitor
Control Power Control, signal sensing on/off
Heat output 1,500 BTU/h
Front panel Glass with removable rack-mounting ears, direct LED illumination; black painted steel chassis
Dimensions (W × H × D) 17½ × 6 1/16 × 21 in (44.45 × 15.4 × 53.3 cm) including feet, front panel and cables; 19 in (48.3 cm) wide with rack ears
Weight 32.5 lb (14.8 kg); shipping 47 lb (24.4 kg)
Warranty 3-year limited (McIntosh USA)

McIntosh MI347 product page and specifications · Owner's manual (PDF) · Brochure (PDF)

Where it sits in the range

McIntosh's multichannel and custom-install amplifiers for home theater and distributed audio, cheapest to dearest.

  • McIntosh MI1250: 12 × 50 W Class D zone amplifier, $4,500
  • McIntosh MI128: 8 × 120 W Class D amplifier, $4,500
  • McIntosh MI502: 2 × 500 W Class D amplifier, $5,000
  • McIntosh MI254: 4 × 250 W Class D amplifier, $6,000
  • McIntosh MI347 (this model): 7-channel Class D theater amplifier, 250 W front and 125 W surround channels, $6,500
  • McIntosh MC257: 7-channel Class A/B amplifier, 200 W per channel, $13,000
  • McIntosh MC303: 3-channel Class A/B amplifier, 300 W per channel through Autoformers, $14,000

The processors are the MX200 and MX124; the MHT300 receiver carries its own seven channels of amplification.

McIntosh purchases are completed in store or by phone or email after a consultation, with pickup at Pearl Audio or delivery and installation within the Portland, Oregon area. McIntosh products are not available for carrier shipment.

Plan your McIntosh system with Pearl Audio

Pearl Audio is an authorized McIntosh dealer. We design and install McIntosh theaters, decide with you between the MI347 and the MC257, and plan the processor, loudspeakers, rack and control around it. Call (503) 222-2599 or email sales@pearlaudio.com.

Signature technologies

The engineering behind the McIntosh MI347 Power Amplifier

McIntosh gives its technologies names because each one solves a specific problem. Here is what each does, where it came from, why it matters in a system, and what you may hear.

Signature technologySince 1977

Power Guard

A comparator that watches the amplifier's input and output waveforms and eases the input drive, in real time, the moment the output begins to clip. Read the deep diveClose

What it does

Every amplifier has a point at which it runs out of clean output and the peaks of the waveform flatten. Power Guard compares the shape of the input signal with the shape of the output signal. The two match until the amplifier reaches its limit; when they diverge, the circuit drives a photo-optical attenuator at the input and reduces the drive just enough to keep the output within its clean range. It acts only when needed and only for as long as the overload lasts, and it does not add power: a 450-watt amplifier remains a 450-watt amplifier.

Why it matters in a system

Hard clipping produces harmonics that sound harsh and, sustained, can burn out tweeters; it is the most common way a good system is damaged at a party. Power Guard lets a McIntosh amplifier be driven to its limit without that risk, which matters most with low-sensitivity loudspeakers, large rooms and recordings with wide dynamic range. In a home theater it means a seven-channel MC257 or a Class D MI-series amplifier can be run hard on a film soundtrack without harm. Two amber indicators show when the circuit is working; if you see them often, the system needs more amplifier, not more volume.

What you may hear

Demanding peaks that stay musical instead of turning hard, and the confidence to listen at realistic levels. Most owners never see Power Guard act, which is the point. On the MA252 and MA352 the small-signal tubes flash amber when it does.

Signature technologySince 1967

Sentry Monitor

Fuseless protection that watches the output current and disengages the output stage before the current can reach a damaging level, then resets itself when the fault clears. Read the deep diveClose

What it does

A shorted loudspeaker cable, a failed driver or a brutal passage into a very low impedance can ask an output stage for more current than its devices can survive. Sentry Monitor measures the output current continuously and, at the threshold McIntosh sets for each model, disconnects the output stage in a fraction of a second. There is no fuse in the signal path to replace and nothing to degrade the sound; when the condition returns to normal the circuit re-engages on its own. On the tube amplifiers the small-signal tubes flash red when it has acted.

Why it matters in a system

Output protection is usually a fuse (slow, and audible as a resistance in the signal path) or a relay that trips late. Sentry Monitor is neither, and it has been on every McIntosh solid-state amplifier since the company's first transistor designs, which is one reason McIntosh amplifiers from the 1970s are still in daily use. In a system it is the insurance that lets you run long speaker cables, bi-wire, or drive a demanding loudspeaker without worrying about the one bad connection that ends an evening.

What you may hear

Nothing, unless something is wrong. If playback stops and the indicators show a fault, correct the cause, follow the reset instructions in the owner's manual for your model, and the amplifier is back. There is no fuse to find.

System integration

Power Control

A low-voltage control link between McIntosh components: switch the preamplifier on and the amplifier, player, turntable and streamer wake with it, with their meter lighting following along. Read the deep diveClose

What it does

Every McIntosh component carries Power Control jacks. A three-conductor cable runs from the preamplifier's POWER CONTROL MAIN (or a Trigger output) to the POWER CONTROL IN of the next component, and on down the chain; the power command and the meter-illumination command travel on that one cable. On a power amplifier a rear switch sets the behavior: REMOTE follows the preamplifier, ON keeps the amplifier on regardless, OFF keeps it off. The C55 and C2800 provide a Main output and four Trigger outputs so a complex system, or a second zone, can be sequenced; Data ports and IR inputs carry the remote-control commands alongside.

Why it matters in a system

A separates system is only as pleasant to live with as its first thirty seconds. Power Control turns a rack of McIntosh components into one instrument that comes to life from a single button and shuts down the same way, with the amplifiers' lighting switching with the rest. It also lets the Eco power-management feature on current amplifiers be used safely: an amplifier that has switched itself off after a period of silence returns the moment the preamplifier wakes it. The matching McIntosh Power Control Cables are available in several factory lengths; Pearl Audio can specify the right ones for your rack.

What you may hear

Nothing, by design; Power Control carries commands, not audio. What you notice is a system that behaves as one component, and meters that light together.

All McIntosh technologies and the company story

The McIntosh story

Seventy-seven years of American engineering you can see working: the Unity Coupled transformer, the Autoformer, the blue meter and the glass panel, still made in Binghamton.

Founded 1949 in Silver Spring, Maryland (in Binghamton, New York since 1951) by Frank H. McIntosh and Gordon J. Gow · mcintoshlabs.com

Milestones

  1. 1949 Founded on the Unity Coupled Circuit Frank H. McIntosh and Gordon Gow found McIntosh in Silver Spring, Maryland. U.S. Patent 2,477,074 covers the Unity Coupled Circuit; the 50W-1 is the first product, the AE2 preamplifier follows in 1950.
  2. 1951 Binghamton, New York The company moves to the second floor of 320 Water Street in Binghamton; Sidney Corderman joins as head of research, engineering and development and stays forty years. The factory at 2 Chambers Street, built in eight months in 1956, is still home.
  3. 1954 MC30, MC60 and the chrome chassis The MC30 and MC60 establish the chrome chassis as a McIntosh design element; the C8 preamplifier shows that industrial design matters; the MR55 of 1957 is the first McIntosh tuner.
  4. 1961 MC275 The MC275 stereo tube amplifier arrives with the MC225 and MC240. Discontinued in 1971, it returns in 1993 and has been in production since; today in its sixth generation.McIntosh MC275 Power Amplifier
  5. 1963 C22 and the illuminated glass panel The C22 tube preamplifier (1963-1972) pairs with the MC275. Through the 1960s McIntosh develops the back-printed glass front panel: gold lettering by day, teal by night.McIntosh C22 Preamplifier Mk V
  6. 1967 Solid state, with Autoformers The MC2505 and MC2105 are McIntosh's first transistor amplifiers: output Autoformers, Sentry Monitor protection, illuminated output meters and an all-glass front panel, the template for every McIntosh amplifier since.McIntosh MC462 Power Amplifier
  7. 1969 Woodstock McIntosh amplifiers, by most accounts about twenty MC3500 tube monoblocks, power the Woodstock festival.
  8. 1974 The Wall of Sound On March 23 the Grateful Dead unveil the Wall of Sound at the Cow Palace: 48 McIntosh MC2300 amplifiers, 28,800 watts. The MR78 FM tuner of 1972 belongs to the same years.
  9. 1977 Power Guard The MC2205 is the first amplifier with Power Guard, the anti-clipping comparator carried by every McIntosh amplifier since. Frank McIntosh retires; Gordon Gow becomes president.
  10. 1980 XRT20 line array and MC2500 The XRT20 brings line-array loudspeakers into the home and the MC2500 (1980-1990) becomes the big stereo amplifier of the decade; the MCD7000 is the first McIntosh CD player.McIntosh XRT2.1K Floorstanding Loudspeaker
  11. 1993 Gordon Gow Commemorative MC275 After Gow's death in 1989 and the 1990 sale to Clarion, the MC275 returns as a commemorative edition and never leaves the line again.
  12. 1999 50 years: the MC2000 Sidney Corderman comes out of retirement to design the MC2000, a limited-edition vacuum-tube amplifier for the company's fiftieth anniversary.
  13. 2000 Quad Balanced and a new president The MC1201 monoblock introduces the Quad Balanced architecture behind today's MC1.25KW, MC611 and MC462. In 2001 Charlie Randall, an engineer with the company since 1988, becomes president and CEO.McIntosh MC1.25KW Power Amplifiers (pair)
  14. 2007 MT10 turntable Two years after the Reference System of 2005, McIntosh introduces its first turntable, the MT10, with an illuminated speed meter and McIntosh green platter.McIntosh MT10 Precision Turntable
  15. 2017 Hybrid Drive and the digital module The MA252 is the first McIntosh hybrid integrated amplifier; the DA1 Digital Audio Module makes the digital section replaceable. Frank McIntosh and Gordon Gow enter the Consumer Technology Hall of Fame.McIntosh MA252 Integrated Amplifier
  16. 2019 70th anniversary The MC2152 amplifier and C70 preamplifier mark 70 years; the MC901 puts a tube and a solid-state amplifier on one chassis; the DA2 module arrives. The MC1502 and C22 Mk V carry the anniversary designs forward.
  17. 2024 75 years, and Bose McIntosh marks its 75th anniversary. In November, Highlander Partners (owner since 2022) sells McIntosh Group, parent of McIntosh and Sonus faber, to Bose Corporation. Manufacturing stays in Binghamton.
  18. 2026 MA2375 In June the MA2375 becomes the first McIntosh vacuum-tube integrated amplifier in more than a decade: Unity Coupled transformers, Sentry Monitor and Power Guard SGS in one 75-watt chassis.McIntosh MA2375 Vacuum Tube Integrated Amplifier
  19. Now McIntosh MI347 Power Amplifier The MI347 is McIntosh's seven-channel Class D home theater amplifier, 250 watts for the three front channels and 125 watts for four surrounds into 8 ohms, with Power Guard and Sentry Monitor.
Read the McIntosh story
McIntosh MC275 vacuum tube amplifier, low angle

McIntosh Laboratory was founded in 1949 in Silver Spring, Maryland, by Frank H. McIntosh, a radio engineer who had run a Washington consulting practice, and Gordon J. Gow, the young engineer he had hired in 1946 to help build an amplifier that did not yet exist: one that could deliver real power across the whole audible band with distortion below one percent. Their answer was the Unity Coupled Circuit, patented in 1949 as U.S. Patent 2,477,074, which wound the output transformer into the operating circuit of the tubes with paired plate and cathode windings. The 50W-1 amplifier that carried it was the company's first product, and the AE2 of 1950 its first preamplifier. In 1951 the company moved to the second floor of a building in Binghamton, New York, where Sidney Corderman joined as head of research, engineering and development; the factory McIntosh still occupies at 2 Chambers Street opened in 1956.

The 1950s and 1960s made the McIntosh look. The MC30 and MC60 of 1954 and 1955 established the chrome chassis, the C8 preamplifier showed that industrial design mattered, and the MR55 of 1957 was the first McIntosh tuner. Through the 1960s the company developed the front panel it is known for: a sheet of glass, screen-printed from the back in an ink McIntosh made itself, so the lettering reads gold under room light and glows teal in the dark and never wears off. The stereo tube amplifiers of the decade, the MC225, MC240 and MC275 of 1961, with the C22 preamplifier of 1963, are the designs collectors chase today; the MC275 has been back in production since 1993 and the C22 is in its fifth version. Dave O'Brien spent those years on the road running the McIntosh Performance Clinics, bench-testing customers' amplifiers of every make in dealers' stores, a tradition of measured proof that the company has never given up.

McIntosh's history runs through the music of the period. In 1969 McIntosh amplifiers, by most accounts about twenty MC3500 tube monoblocks, powered Woodstock. On March 23, 1974, the Grateful Dead unveiled the Wall of Sound at the Cow Palace with 48 McIntosh MC2300 solid-state amplifiers delivering 28,800 watts. The MC2300 belonged to the transistor generation McIntosh had begun in 1967 with the MC2505 and MC2105, the first solid-state amplifiers to keep output transformers, which McIntosh called Autoformers, so that the amplifier delivered full power into any loudspeaker impedance; the same amplifiers introduced Sentry Monitor protection, the illuminated output meters and the all-glass front panel. The MC2205 of the late 1970s added Power Guard, the anti-clipping circuit that has been on every McIntosh amplifier since. Frank McIntosh retired in 1977 and Gordon Gow became president; the XRT20 of 1980 brought line-array loudspeakers into the home, and the MCD7000 was the company's first CD player.

Gow died in 1989 and the company was sold to Clarion of Japan in 1990, the year Frank McIntosh also died; the MC275 returned in 1993 as the Gordon Gow Commemorative edition. D&M Holdings bought McIntosh in 2003; Fine Sounds of Milan, parent of Sonus faber and Audio Research, bought it in 2012; a management buyout in 2014 led to the group's renaming as McIntosh Group and its move to New York; Highlander Partners acquired the group in June 2022 and sold it to Bose Corporation in November 2024. Through all of it the company stayed in Binghamton, and since 2001 it has been led by Charlie Randall, an electrical engineer who joined in 1988 and rose through engineering to president. The MC1201 of 2000 brought the Quad Balanced architecture that defines today's big amplifiers; the Reference System of 2005, the MT10 turntable of 2007, the first hybrid integrated amplifier (the MA252 of 2017), the replaceable DA1 and DA2 digital modules, and the 70th-anniversary MC2152 and C70 of 2019 mark the modern era. Frank McIntosh and Gordon Gow were inducted into the Consumer Technology Hall of Fame in 2017.

The McIntosh of 2026 still winds its transformers by hand at 2 Chambers Street, still prints its glass panels in the building, and still tests every component on the bench before it ships. The MA2375 of June 2026, the first McIntosh vacuum-tube integrated amplifier in more than a decade, carries the Unity Coupled transformers of 1949, the Sentry Monitor of 1967 and a tube form of the Power Guard of 1977 in one chassis, which is as good a summary of the company as any. Pearl Audio holds the largest McIntosh inventory in Oregon.

The complete McIntosh story and technology library

McIntosh at Pearl Audio

Pearl Audio has represented McIntosh since 2005, the year the store was founded, and is the longest-running McIntosh dealer in the Northwest. McIntosh has designated Pearl a Platinum dealer, its mark for its largest showrooms, since our second year with the brand. Two decades on, McIntosh remains the brand we commit to most deeply: we hold the largest McIntosh inventory in Oregon, keep the core of the range on the floor in Portland, and our staff are McIntosh factory trained. McIntosh components are sold for in-store pickup or for local delivery and installation in the Portland area; we do not ship them by carrier.

The Pearl Audio experience

How we work with you

A system at this level should be heard, thoughtfully matched, and properly set up. From the first audition to long-term ownership, you work with the same people, in person.

  1. 01

    Listen first

    Hear the MI347 Power Amplifier by appointment in one of our two purpose-designed demonstration rooms, with your own music and time to compare without pressure.

  2. 02

    Delivery and installation

    We deliver and install throughout the Portland area, taking care of placement, connections, ventilation and system configuration ourselves.

  3. 03

    Support for as long as you own it

    We support everything we sell for as long as you own it, whether the answer comes by phone, in your home, or through factory service.

  4. 04

    A path for what comes next

    Trade-in assistance and qualifying 100% Trade-Up options give you flexibility when your listening priorities or your system change.

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