Audio T Verdict
The Musical Fidelity M5si is a high-power integrated amplifier combining a separate pre-amplifier section with two independent mono power-amplifier sections inside one full-width chassis.
It delivers 150 watts per channel into 8 ohms and provides four analogue line inputs, a moving-magnet phono stage, asynchronous USB audio, fixed and variable line outputs and a switchable home-theatre bypass.
It does not include network streaming, Bluetooth, conventional coaxial or optical digital inputs, or a headphone socket. The M5si is best considered a powerful conventional amplifier with carefully chosen vinyl, computer-audio and system-expansion facilities.
Musical Fidelity M5si Integrated Amplifier
The Musical Fidelity M5si is a Class A/B integrated amplifier rated at 150 watts per channel into 8 ohms.
Internally, it uses two independent mono power-amplifier sections and a separate pre-amplifier section mounted on a single circuit board. This arrangement is designed to reduce interaction between channels while retaining the convenience of one chassis.
Its input selection covers conventional line-level sources, moving-magnet vinyl playback and asynchronous USB audio from a compatible computer.
An Amplifier, Not an All-In-One Music System
The standard M5si does not contain a network streamer, Wi-Fi, Bluetooth, internet radio or an HDMI connection.
Its USB Type B socket is a computer-audio input operating at up to 24-bit/96kHz. It does not accept USB memory sticks, and there are no coaxial or optical digital inputs.
Directly Supported Sources
- CD players and streamers with analogue RCA outputs
- Moving-magnet and suitable high-output MC cartridges
- Computers with a compatible USB audio connection
- Tuners, DACs and other conventional line-level sources
- Home-cinema processors with a controlled front-channel output
Requires Additional Equipment
- Low-output moving-coil cartridges require a suitable phono stage or step-up device
- Optical and coaxial sources require an external DAC
- Network streaming requires a separate streamer
- Headphones require a separate headphone amplifier
- Passive loudspeakers and speaker cables are required
150 Watts per Channel
Musical Fidelity rates the M5si at 150 watts per channel into 8 ohms, with both channels driven through two independent power-amplifier sections.
The manufacturer specifies 35V RMS at the onset of clipping, 62 amps peak-to-peak current delivery and a damping factor of 36.
These figures indicate substantial power and current reserves, but loudspeaker suitability still depends on impedance, sensitivity, room size and intended listening level. Difficult loudspeakers should be auditioned with the amplifier rather than assumed compatible from wattage alone.
Separate Pre-Amplifier and Mono Power Sections
The M5si is arranged internally as a pre-amplifier feeding two independent mono power-amplifier sections.
Although all three sections share a chassis and main circuit board, Musical Fidelity uses careful layout and circuit separation to reduce unwanted interaction.
Two pairs of output devices are used per channel, while the amplifier's specified frequency response extends from 10Hz to 20kHz within +0dB and -0.1dB.
Four RCA Line Inputs
Four stereo RCA line inputs are labelled CD, Tuner, AUX1/HT and AUX2.
The labels are provided for convenience: a conventional fixed-level streamer, DAC, cassette deck or another line-level source can use any input configured for normal line operation.
A turntable must not be connected to these inputs unless it already includes a suitable phono stage. Use the dedicated Phono input for a directly compatible cartridge.
Moving-Magnet Phono Stage
The dedicated Phono input is designed for moving-magnet cartridges and suitable high-output moving-coil cartridges.
Musical Fidelity specifies a nominal sensitivity of 3mV, suitability for cartridges producing approximately 1.5mV or more, a 50k-ohm input impedance and RIAA/IEC response within ±0.5dB from 20Hz to 20kHz.
A conventional low-output moving-coil cartridge requires a compatible external MC phono stage or step-up transformer. Cartridge output and loading requirements should be checked before connection.
Turntable Grounding
A grounding post is provided for turntables fitted with a separate earth lead.
Musical Fidelity advises connecting the lead when excessive hum is present rather than assuming that every turntable requires it. If grounding makes the hum worse, disconnect the lead and investigate the wider system for an earth loop.
Phono cables should be well screened and routed away from mains and speaker cables because the cartridge signal is particularly small.
Switchable AUX1 and Home-Theatre Input
The rear-panel AUX/HT switch changes the AUX1 sockets between a normal line input and a home-theatre bypass.
In AUX mode, the M5si's volume control sets the listening level. In HT mode, the M5si volume control is bypassed and level must be controlled by the connected surround processor or pre-amplifier.
Important Home-Theatre Bypass Warning
HT mode is fixed gain. Never connect a normal fixed-output CD player, streamer, DAC or other uncontrolled source while the rear switch is set to HT.
Begin setup with the connected processor's volume fully reduced. An uncontrolled signal through the bypass can produce extremely high volume and may damage loudspeakers or hearing.
Asynchronous USB Audio
The rear USB Type B socket accepts an asynchronous audio stream from a compatible computer at up to 24-bit/96kHz.
Audio files are decoded by the computer's playback software and sent to the M5si as USB audio. File compatibility therefore depends on the computer and software rather than the amplifier reading MP3, FLAC, WAV or AAC files itself.
Use a suitable USB Type A to Type B cable and avoid sharing the same USB bus through a heavily loaded hub if dropouts occur. Compatibility with a specific current operating system should be confirmed where computer audio is an important requirement.
No Coaxial or Optical Digital Inputs
USB is the M5si's only built-in digital input. A television, CD transport or streamer providing only coaxial or optical output requires an external DAC with an analogue RCA connection to the amplifier.
The M5si also has no HDMI ARC or eARC input. Television integration should therefore be planned around an external DAC, analogue television output or a suitable home-cinema processor.
Fixed Line Output
The Line Out sockets carry the currently selected analogue signal at a constant level unaffected by the M5si volume control.
This output can feed a recorder, monitoring device or separate headphone amplifier with its own volume control.
Do not use the fixed Line Out to drive a power amplifier or active loudspeakers unless the connected equipment provides a suitable independent volume control.
Variable Pre-Amplifier Output
The Pre Out sockets follow the M5si's volume control and provide the correct output for a compatible external power amplifier, bi-amplified system or active subwoofer requiring a variable line-level signal.
The pre-output is full-range rather than a dedicated filtered subwoofer connection. Crossover frequency, phase and level must therefore be set on the subwoofer itself.
When bi-amplifying passive loudspeakers, follow the loudspeaker manufacturer's instructions and remove terminal linking plates where required before switching on the system.
Single Pair of Speaker Outputs
One stereo pair of binding posts connects the left and right passive loudspeakers and accepts compatible 4mm banana plugs or suitably prepared bare cable.
The M5si does not provide selectable Speaker A and Speaker B zones. Bi-wiring must be arranged from the single pair of amplifier terminals where the speaker manufacturer supports it.
Observe consistent polarity at both ends and check that no loose conductor strands can short adjacent terminals.
System Trigger Connections
Trigger input and output connections allow compatible Musical Fidelity and system-control equipment to coordinate power and standby operation.
Trigger connections carry control voltage rather than audio and should only be used with compatible equipment and the correct cable type.
Remote Control
The supplied M5s system remote controls amplifier volume, mute and input selection.
It also contains controls for compatible Musical Fidelity CD players, allowing a matching source and amplifier to share one handset.
The amplifier's mute function is remote-controlled, while the front-panel buttons provide direct source selection and the central control adjusts volume.
Installation and Ventilation
Position the 14.6kg amplifier on a stable, level support capable of carrying its weight.
The top and bottom ventilation openings must remain clear. Musical Fidelity does not recommend enclosing the amplifier in a cabinet or placing it where airflow is obstructed.
Switch the system off before changing source, speaker, pre-output or home-theatre connections. After switch-on, the speaker outputs remain muted for approximately six seconds while the amplifier settles.
Black or Silver Finish
The M5si is available with a black or silver fascia, subject to current stock and availability.
Both versions use the same internal amplifier, connection layout and supplied functionality, so the choice is cosmetic.
Key Features
- Class A/B integrated amplifier
- 150 watts per channel into 8 ohms
- Separate pre-amplifier and dual-mono power-amplifier sections
- Four stereo RCA line inputs
- Switchable AUX1 and fixed-gain home-theatre bypass
- Moving-magnet phono stage
- Suitable for selected high-output moving-coil cartridges
- Asynchronous USB Type B input up to 24-bit/96kHz
- Fixed Line Out for recording or a headphone amplifier
- Variable Pre Out for a power amplifier or active subwoofer
- One stereo pair of speaker binding posts
- System trigger input and output
- Remote volume, mute and source selection
- Black or silver finish
Frequently Asked Questions
How powerful is the M5si?
Musical Fidelity rates it at 150 watts per channel into 8 ohms. Speaker impedance, sensitivity and room size should still be considered when assessing compatibility.
Does it have a built-in phono stage?
Yes. The Phono input is designed for moving-magnet and suitable high-output moving-coil cartridges producing approximately 1.5mV or more.
Can I use a low-output moving-coil cartridge?
Not directly. A conventional low-output MC cartridge requires a suitable external moving-coil phono stage or step-up device connected to a line input.
Does it have a built-in DAC?
It includes USB digital-to-analogue conversion for a compatible computer at up to 24-bit/96kHz. It does not provide coaxial, optical or HDMI digital inputs.
Can I connect a USB memory stick?
No. The USB Type B socket is a computer-audio input and does not browse or play files directly from USB storage.
Can I connect a television?
A television with an adjustable analogue output can use a normal line input. Optical, coaxial or HDMI-only televisions require a suitable external DAC or home-cinema processor.
What is the difference between Line Out and Pre Out?
Line Out is fixed and unaffected by the M5si volume control. Pre Out is variable and follows the amplifier's volume setting.
Can I connect an active subwoofer?
Yes. Use the variable Pre Out with a subwoofer that provides a line-level input and its own crossover, level and phase controls.
What does HT mode do?
It bypasses the M5si volume control for the AUX1 input so a home-cinema processor can control level. Never use HT mode with an uncontrolled fixed-output source.
Does it have a headphone socket?
No. A separate headphone amplifier with its own volume control can be connected to the fixed Line Out.
Why Buy From Audio T?
- Independent amplifier and loudspeaker matching advice
- Moving-magnet and moving-coil cartridge compatibility checks
- Home-theatre bypass setup guidance
- USB computer-audio assistance
- Subwoofer, pre-output and bi-amplification advice
- In-store demonstrations through participating branches
- Part-exchange options on suitable equipment
- Home demonstration support where available
- Ongoing system setup and servicing advice
Contact your local Audio T store
to discuss availability, arrange a demonstration and confirm compatibility with your loudspeakers and sources.