Marantz MM7055 Five-Channel Power Amplifier

Five Channels to Take the Load Off Your Receiver

An AV receiver spreads one power supply across nine or eleven channels. The MM7055 does one job instead. It hands 140 watts to a channel into 8 ohms, or 170 watts into 6 ohms, measured from 20 Hz to 20 kHz with two channels driven.

Marantz also quotes a maximum effective output of 210 watts per channel into 6 ohms at 1 kHz. Five channels covers left, center, right and both surrounds, which is the part of a room that does most of the work.

Both Kinds of Input, on Every Channel

Each of the five channels has a balanced XLR jack and an unbalanced RCA jack, switchable channel by channel. Input sensitivity is 1.2 volts on RCA and 2.4 volts on XLR. Around the back you also get a DC trigger in and out and a flasher input.

Why It Weighs Less Than You Expect

Marantz mounts the output devices on a chimney-shaped heat sink and moves the air with cooling fans rather than piling on metal. A temperature sensor sets fan speed against the heat being made, so the amplifier stays quiet when it is only idling.

The result is 15.2 kg, about 33 pounds, from a chassis 440 mm wide and 183 mm tall. A large EI-core transformer supplies the whole amplifier. Draw is 400 watts in use and 0.4 watts on standby.

The Rest of the Numbers

Signal-to-noise ratio is 105 dB. Damping factor is 100. Frequency response runs from 8 Hz to 100 kHz within 3 dB. A power cord is in the box, and the finish is black.

What Reviewers Are Saying

Steve Munz, in a hands-on preview for Audioholics on June 9, 2016: "the MM7055 was devoid of audible transformer hum as well as hiss through my speakers."

Who Is This Five-Channel Amplifier Best For?

• Your receiver is stretched thin — handing the five main channels to their own amplifier frees the receiver to do the processing, and the speakers get power that is not being shared eleven ways
• You listen late and quietly — a temperature sensor holds the fans to the lowest speed the heat allows, so the amplifier keeps out of the way during a quiet passage or a late film
• You need it to lift into a rack — active cooling let Marantz use less heat-sink metal, so this is a 33 pound amplifier rather than a 60 pound one
• Your processor mixes output types — every channel takes XLR or RCA and switches independently, so a mixed set of preamp outputs is no obstacle
• Check your speakers first — Marantz publishes ratings into 8 and 6 ohms only, and the manual asks for speakers of 6 ohms or more; if yours are 4 ohm designs, pick one of our multi-channel amplifiers rated to drive that load instead

How Does It Connect to Your System?

Run five preamp outputs from your receiver or processor into the amplifier, then set each channel to XLR or RCA to match. The speaker terminals are screw type and well spaced. For cable heavier than 14 gauge, banana plugs seat more easily than bare wire.

Wire the DC trigger to your processor and the amplifier switches on with it. A trigger output carries the signal to the next component, and a flasher input lets a control system drive it instead.

Pairs Well With

A power amplifier needs a few things around it. These are the categories most MM7055 owners shop next.

• Home theater receivers — the preamp outputs that feed all five channels
• Interconnect cables — five balanced XLR or unbalanced RCA runs from the processor
• Speaker cables — banana-terminated wire suits these terminals best
• Power conditioners — a clean feed for an amplifier that draws 400 watts

Frequently Asked Questions

Do I need a receiver or processor with this amplifier?

Yes. The MM7055 supplies power and nothing else. Feed it from the preamp outputs of an AV receiver or a surround processor.

How much power does it make?

140 watts per channel into 8 ohms and 170 watts into 6 ohms. Marantz measures that from 20 Hz to 20 kHz with two channels driven, and quotes 210 watts maximum effective output into 6 ohms at 1 kHz.

Can I mix XLR and RCA between channels?

You can. Each channel has its own input switch, so five channels can be set five different ways if your processor requires it.

Are the cooling fans audible?

Marantz calls them exceptionally quiet, and a temperature sensor keeps their speed as low as the heat allows. Install the amplifier somewhere with air around it and they work less.

How heavy is it?

15.2 kg, or about 33 pounds. That is light for a five-channel amplifier because active cooling replaces much of the heat-sink metal.

What is the flasher input for?

It lets a control box or automation system operate the amplifier, which matters in a custom install where the front panel is behind a door.

See It in Action

OldTrades spends thirteen minutes unboxing the MM7055:

Hometheater Enthusiast unboxes one and looks it over:

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