What Does the Marantz MM7055 Do?

The MM7055 takes five line-level signals from a compatible AV processor, preamplifier or AV receiver and supplies the amplified outputs needed to drive five passive loudspeakers.

It can form the power-amplifier section of a complete separates-based home cinema system. It can also supplement an AV receiver by taking responsibility for five channels while the receiver continues to power the remaining speakers.

The exact channel assignment is determined by the connected processor or receiver. For example, the MM7055 could power the front left, centre, front right and two surround speakers. In a larger system it could instead be assigned to surround, surround-back or height speakers, subject to the processor’s pre-out and amplifier-assignment options.

Five Channels of Class A/B Power

Marantz equips the MM7055 with five Class A/B amplifier channels, each based on current-feedback topology. Current-feedback amplification is designed to provide wide operating bandwidth and a fast response to changing audio signals.

The manufacturer specifies 140W per channel into 8 ohms and 170W per channel into 6 ohms from 20Hz to 20kHz at 0.08% total harmonic distortion, with two channels driven. A maximum effective output of 210W per channel into 6 ohms is also specified at 1kHz with two channels driven.

Those measurement conditions are important when comparing the MM7055 with other power amplifiers. The 140W figure should not be interpreted as a published all-five-channels-driven measurement. Real system performance will also depend on programme material, speaker impedance, listening level, room size and ventilation.

Current-Feedback Amplifier Topology

The MM7055 uses Marantz current-feedback circuitry across its five channels. This design is intended to maintain a wide frequency response while responding quickly to dynamic changes in music and film soundtracks.

Each channel also has its own input buffer amplifier. This provides a consistent interface between the connected processor and the power-amplifier stage, whether the selected connection is balanced XLR or unbalanced RCA.

EI-Core Transformer and Energy Storage

A power amplifier must supply rapidly changing current to several loudspeakers while maintaining stable operation. Marantz equips the MM7055 with a multiple-secondary EI-core transformer and more than 65,000µF of custom-designed energy-storage capacity.

This substantial power-supply section supports the five output channels during demanding soundtrack passages. Marantz also uses selected and customised internal components as part of the amplifier’s overall design.

Balanced XLR and Unbalanced RCA Inputs

Every amplifier channel has one balanced XLR input and one unbalanced RCA input. A dedicated selector beside each channel determines which connection is active, so balanced and unbalanced connections can be mixed across the five channels when required.

Balanced XLR connections can be useful in systems with a compatible processor, particularly where longer interconnects are needed or several system components are installed together. RCA connections provide broad compatibility with AV receivers and processors that offer conventional unbalanced pre-outs.

The type of connector alone does not determine sound quality. Cable length, the output design of the processor, grounding and correct system installation all matter. Audio T can advise whether balanced or unbalanced connection is the more appropriate choice for a particular installation.

Five Loudspeaker Outputs

Five sets of binding-post speaker terminals are provided, corresponding to the five amplifier channels. Channel labelling helps maintain the correct relationship between the processor outputs and the connected speakers.

Marantz instructs users to connect speakers with a nominal impedance of 6 ohms or greater. Speaker polarity must also be maintained, with positive connected to positive and negative connected to negative.

Care should be taken to prevent loose conductor strands from touching another terminal or the amplifier chassis. A short circuit can activate the MM7055’s protection system and may damage connected equipment.

Powering a 5.1 Home Cinema System

The MM7055 is particularly straightforward when used with a five-channel AV processor. Its five outputs can drive the front left, centre, front right, surround left and surround right passive loudspeakers in a conventional 5.1 system.

The “.1” channel is different. An active subwoofer contains its own power amplifier and is normally connected directly to the processor’s subwoofer or LFE pre-output. The MM7055 does not provide a powered subwoofer channel.

Explore Audio T’s ranges of home cinema speakers and active subwoofers when planning a complete system.

Adding External Power to an AV Receiver

The MM7055 can be partnered with a compatible AV receiver when that receiver provides variable pre-amplifier outputs for the required channels. The receiver continues to perform input switching, HDMI management, decoding, room correction and volume control, while the MM7055 powers the assigned speakers.

This arrangement may reduce the workload placed on the receiver’s internal amplifier section. It can also provide greater freedom when configuring larger systems that require more powered channels than the AV receiver can supply internally.

The precise options vary between receivers. Pre-out availability, amplifier assignment and maximum processing-channel capacity must all be checked. The Marantz CINEMA 40, for example, offers multichannel pre-outs that allow suitable external power amplifiers to be incorporated into a larger installation.

Supporting the Front Soundstage

The front left, centre and front right loudspeakers carry much of the soundtrack’s dialogue, music and on-screen action. Assigning these channels to the MM7055 leaves two further amplifier channels available for a surround pair or another compatible speaker group.

This can be a useful configuration when the front speakers are relatively demanding or when consistent amplification across the front soundstage is a priority. Speaker sensitivity, impedance behaviour, listening distance and target volume should all be considered before deciding whether this is the best assignment.

Surround and Height-Channel Expansion

In a larger Dolby Atmos or DTS:X system, the five MM7055 channels can be assigned to surround, surround-back or height speakers if the connected processor provides the corresponding pre-outs and configuration options.

The MM7055 itself does not decode Dolby Atmos, DTS:X or any other surround format. The processor determines the audio format, performs channel routing and controls the overall level. The power amplifier simply drives the loudspeakers assigned to its five inputs.

Browse Audio T’s wider range of home cinema amplifiers and AV receivers for compatible processing and amplification options.

DC Trigger and System-Control Connections

A DC control input allows a compatible processor to switch the MM7055 between operating and standby states as part of the complete system. A corresponding output can pass the control signal to another compatible component.

Flasher input and Marantz remote-control connections provide additional installation options. These connections can be useful when the amplifier is positioned inside suitable furniture or operated as part of a coordinated Marantz system.

No handheld remote control is supplied because everyday volume and source control take place at the connected processor or receiver. A Marantz remote-control cable is included for compatible system-control applications.

Automatic Standby

The MM7055 includes a selectable automatic standby function. When enabled, the amplifier can enter standby after more than 30 minutes without an input signal or control operation.

Marantz states that this function is switched off at the factory. It can be enabled using the front-panel control procedure if automatic power management is preferred.

Thermal Management and Protection

The output stages are mounted on an extruded aluminium thermal tunnel designed to dissipate heat efficiently. Temperature-controlled cooling fans provide further support when internal operating temperatures rise.

Protection circuitry monitors conditions such as excessive temperature, overload and abnormal speaker connections. If a problem is detected, the amplifier can enter standby to protect its internal components and the connected system.

MM7055 or Marantz AMP 30?

The MM7055 offers five channels of traditional Class A/B amplification rated at 140W per channel into 8 ohms under Marantz’s stated two-channel test conditions. It is a strong option for established systems needing five external power channels and conventional XLR or RCA connectivity.

The newer Marantz AMP 30 occupies a higher position in the range, with six channels, greater rated output and additional configuration flexibility. It may suit a more ambitious installation, but its higher specification and price will not be necessary for every system.

An Audio T demonstration and system assessment can help determine which model provides the most appropriate number of channels, power capability and upgrade potential.

System Matching and Installation

Successful integration starts with the processor. It must provide variable line-level pre-outs for every MM7055 channel being used. Fixed-level source outputs should not be connected directly because the MM7055 has no volume control.

The loudspeakers must also meet Marantz’s impedance guidance, while suitable interconnects, correctly terminated speaker cables and adequate equipment support are required. Channel assignments and level calibration should then be completed through the processor.

Room-correction measurements should normally be repeated after changing amplifiers, speakers, channel assignments or subwoofer integration. This allows the processor to recalculate channel levels, distances and frequency correction for the completed system.

Explore more Marantz products available from Audio T, or browse our complete home cinema and AV range.