Audio T Verdict
The Rega Aos MC is a serious moving-coil phono stage positioned between the compact Fono MC Mk4 and the flagship Aura Reference MC.
Its two-stage, fully analogue circuit is based heavily on the Aura, using carefully matched low-noise FETs, symmetrical Class A amplification and separate passive and active sections for the RIAA equalisation.
Four resistance settings, two capacitance settings and two gain levels make it compatible with a broad range of conventional low-output moving-coil cartridges. It is factory configured for Rega's Ania, Ania Pro, Apheta 3 and Aphelion 2 cartridges.
The Aos MC is more substantial than the Fono MC Mk4, with an internal linear power supply, full aluminium half-width case and greater circuit sophistication. It remains simpler than the Aura, with RCA connections only and no front-panel loading, mute or mono controls.
Rega Aos MC Moving Coil Phono Stage
The Rega Aos MC is a dedicated external phono pre-amplifier designed for low-output moving-coil cartridges.
Its circuit is based heavily on Rega's Aura Reference MC phono stage and uses two symmetrical Class A amplification stages to provide the gain and RIAA equalisation required for vinyl playback.
The Aos MC is housed in a custom Rega half-width aluminium case with an internal mains power supply, selectable cartridge loading, two gain settings and automatic standby.
It is a purely analogue component and contains no digital signal processing, software control, USB connection or wireless circuitry.
What Does a Moving-Coil Phono Stage Do?
A low-output moving-coil cartridge generates an extremely small electrical signal, usually measured in fractions of a millivolt.
This signal is far below the level required by a conventional amplifier line input and is also recorded using the standard RIAA frequency curve.
The Aos MC therefore performs two essential tasks:
- It amplifies the low-level cartridge signal to a usable line level
- It applies the inverse RIAA curve to restore the correct frequency balance
A moving-coil phono stage must perform this amplification while adding as little noise and distortion as possible, which is why circuit design, earthing, power supply and physical positioning are particularly important.
Dedicated Low-Output Moving-Coil Design
The Aos MC has been designed for conventional low-output moving-coil cartridges.
It provides much more gain than a moving magnet stage and allows the input resistance, capacitance and gain to be adjusted for different cartridge requirements.
It is not intended for moving magnet cartridges such as the Rega Carbon, Nd3, Nd5, Nd7 or Nd9.
Some high-output moving-coil cartridges are designed to operate through a moving magnet input, so the cartridge manufacturer's recommendation should always be checked before connection.
Low-Output Moving Coil
- Suitable for the Rega Aos MC
- Requires substantial phono-stage gain
- Loading should be matched to the cartridge
- Includes Rega Ania, Ania Pro, Apheta 3 and Aphelion 2
Moving Magnet
- Not suitable for the Rega Aos MC
- Normally requires 47 kO loading
- Produces a considerably higher output
- Consider the Rega Fono MM Mk5 instead
Purely Analogue Circuit
The Aos MC is a two-stage analogue amplifier without digital control circuitry in the signal path.
Rega has deliberately avoided adding functions that are not required for moving-coil playback.
Gain and loading are selected using physical switches on the rear panel rather than a microprocessor, display or application.
The aluminium enclosure helps screen the sensitive high-gain circuitry from radio-frequency interference generated by nearby electronic equipment.
- Two-stage analogue amplifier
- No digital signal processing
- No analogue-to-digital conversion
- No display or software interface
- Physical rear-panel loading controls
- Full aluminium enclosure
Aura-Derived Circuit Design
The core circuit principles used by the Aos MC are based heavily on the Rega Aura Reference MC phono stage.
The first and second amplification stages follow the same broad topology, although the Aura adds a third stage, more loading options, balanced outputs and a considerably larger power supply and enclosure.
The Aos brings many of the fundamental Aura design ideas into a more compact and accessible product.
First Symmetrical Class A Stage
The first stage is a symmetrical complementary Class A amplifier using Linear Systems ultra-low-noise FET transistors.
The FETs are carefully graded and matched before being configured as a compound input pair.
FET devices have an extremely high input impedance and do not require bias current to flow through the cartridge coil.
This helps avoid disturbing the delicate magnetic arrangement within the moving-coil cartridge.
The input configuration also avoids placing coupling components between the cartridge output and the first FET amplification stage.
- Symmetrical complementary Class A input stage
- Linear Systems ultra-low-noise FET transistors
- Carefully graded and matched devices
- Compound input-pair configuration
- No cartridge-coil bias current
- No coupling component between the cartridge and first stage
Passive High-Frequency RIAA Equalisation
The first amplification stage drives the passive high-frequency part of the RIAA equalisation network.
Separating this section from the active low-frequency correction allows each part of the equalisation curve to be handled by the most appropriate circuit.
Rega specifies RIAA accuracy better than plus or minus 0.2 dB between 65 Hz and 70 kHz when used with a 100 kO output load.
Second Symmetrical Class A Stage
The second stage is a symmetrical Class A differential amplifier with a common-base driver section.
This stage provides further amplification and also forms the active low-frequency part of the RIAA equalisation.
Using separate passive and active equalisation sections helps maintain accuracy while avoiding the compromises of applying the complete RIAA curve within one feedback network.
Self-Adjusting Servo Control
The Aos MC includes a self-adjusting servo circuit which compensates for changes caused by ambient and internal operating temperature.
This helps maintain the required operating conditions as the circuit warms up and as the room temperature changes.
The servo operates automatically and does not require user adjustment.
Adjustable Cartridge Loading
Rear-panel DIP switches allow the input resistance, capacitance and gain to be matched to the connected moving-coil cartridge.
Begin with the cartridge manufacturer's recommended loading and change only one setting at a time.
Switch Off Before Changing Settings
Always switch off the Aos MC and partnering amplifier before changing the rear-panel gain or loading switches.
Changing the gain while the system is operating can cause the input circuit to readjust and may produce a loud thump through the loudspeakers.
Four Resistance Settings
Resistive loading affects the electrical damping applied to the cartridge generator.
The Aos MC provides four selectable values:
400 O
Set resistance switches 1 and 2 to Off.
This is the lightest available resistance loading and may suit cartridges specifying a comparatively high load value.
150 O
Set switch 1 to Off and switch 2 to On.
100 O
Set switch 1 to On and switch 2 to Off.
This is the factory resistance setting for Rega moving-coil cartridges.
70 O
Set resistance switches 1 and 2 to On.
This provides the heaviest available resistance loading.
Two Capacitance Settings
Input capacitance is selected using rear-panel switch 3.
1000 pF
Set switch 3 to Off.
This is the factory setting for Rega moving-coil cartridges.
4300 pF
Set switch 3 to On.
This alternative may suit cartridges whose manufacturer recommends additional capacitive loading.
Two Gain Settings
Rear-panel switch 4 selects the amount of amplification applied to the cartridge signal.
69 dB High Gain
Set switch 4 to On.
This is the factory setting for Rega moving-coil cartridges.
Input sensitivity is 75 µV for a rated 200 mV output.
63 dB Low Gain
Set switch 4 to Off.
This provides greater input headroom and may suit cartridges with a comparatively higher output.
Input sensitivity is 145 µV for a rated 200 mV output.
The highest gain setting is not automatically the best choice. Excessive gain can reduce input headroom, make the volume control more sensitive and increase the audibility of background noise.
Factory Settings for Rega MC Cartridges
The Aos MC is supplied configured for Rega's current low-output moving-coil cartridges.
- Input resistance: 100 O
- Input capacitance: 1000 pF
- Gain: 69 dB high gain
- Resistance switch 1: On
- Resistance switch 2: Off
- Capacitance switch 3: Off
- Gain switch 4: On
These settings are suitable for the Rega Ania, Ania Pro, Apheta 3 and Aphelion 2.
Rega Cartridge Compatibility
Rega Ania
The
Rega Ania
is Rega's most accessible handmade moving-coil cartridge.
It is compatible with the factory Aos MC settings, although the more affordable Fono MC Mk4 should also be considered when balancing the overall system budget.
Rega Ania Pro
The
Rega Ania Pro
uses a Vital-profile nude diamond stylus and is a particularly natural partner for the Aos MC.
The combination is well suited to a suitably revealing Planar 6 or Planar 8 system.
Rega Apheta 3
The
Rega Apheta 3
uses a fine-line nude diamond stylus and is an excellent system match for the Aos MC.
It is commonly partnered with the Planar 8 or Planar 10 and can reveal the increased resolution of the Aura-derived circuitry.
Rega Aphelion 2
The
Rega Aphelion 2
is electrically compatible with the factory Aos MC settings.
As Rega's reference production cartridge, it should also be demonstrated with the Aura Reference MC to establish which stage best suits the wider system.
Compatible Third-Party Cartridges
The Aos MC can also be used with many conventional low-output moving-coil cartridges from other manufacturers.
Before setting the rear switches, check the cartridge manufacturer's recommendations for:
- Nominal cartridge output
- Internal cartridge impedance
- Recommended load resistance
- Recommended input capacitance
- Recommended phono-stage gain
Not every cartridge recommendation will match one of the available settings exactly. Audio T can check compatibility and suggest the most appropriate starting point.
Suitable Rega Turntables
Rega Planar 6
The
Rega Planar 6
with Ania Pro provides a natural entry point for an Aos MC system.
The Aos offers a substantial phono-stage upgrade while allowing the turntable and cartridge to be improved separately later.
Rega Planar 8
The
Rega Planar 8
can be specified with an Ania Pro or Apheta 3.
The Planar 8 with Apheta 3 is an especially well-balanced source for the Aos MC.
Rega Planar 10
The
Rega Planar 10
is available with the Apheta 3 or Aphelion 2.
The Aos provides an appropriate high-performance option, although the Aura should also be compared in a suitably revealing system.
Rega Naia
The
Rega Naia
is normally partnered with the Aphelion 2.
The Aos is compatible and provides a more compact alternative to the Aura, while the Aura remains Rega's intended reference-level partner.
How to Connect the Aos MC
- Check the cartridge manufacturer's recommended loading and gain.
- Switch off the Aos MC, amplifier and turntable power supply.
- Set the rear loading and gain switches to the required positions.
- Connect the turntable RCA leads to the Aos MC input.
- Connect the turntable earth wire if the tonearm provides one.
- Connect a stereo RCA interconnect from the Aos MC output to a normal amplifier line input.
- Connect the supplied Rega mains lead.
- Reduce the amplifier volume fully.
- Switch on the Aos MC before switching on the amplifier.
- Select the amplifier input used by the Aos MC and gradually raise the volume.
Connect the Output to a Line Input
Connect the Aos MC output to an amplifier input marked AUX, CD, Line, Tuner or another conventional line-level input.
Do not connect it to a moving magnet or moving-coil phono input. This would apply excessive gain and RIAA equalisation twice, causing severe overload and distortion.
Turntable Earthing
The rear panel includes a signal-earth terminal for turntables and tonearms with a separate earth wire.
Connect the earth wire securely if one is supplied with the tonearm.
Rega tonearms normally earth through the signal cable and do not require a separate earth connection.
If hum is present, check the RCA plugs, earth arrangement, cable routing and proximity to nearby power supplies or amplifier transformers.
Power-Up and Switch-Off Sequence
Rega recommends switching on the Aos MC before the partnering amplifier or power amplifier.
When switching the system off, turn off the amplifier or power amplifier before switching off the Aos MC.
Following this order reduces the risk of a start-up or shutdown transient being reproduced through the loudspeakers.
Keep the amplifier volume low whenever the phono stage is being switched, connected or adjusted.
Automatic Standby
Automatic standby is enabled by default.
After approximately one hour without an input signal, the Aos MC enters its low-power standby state.
Pressing the front-panel power and standby button returns the phono stage to operation.
Automatic standby can be disabled by moving both rear auto-standby switches to their downward positions.
Disabling automatic standby increases electricity consumption when the product is left switched on.
Automatic Standby Enabled
- Both standby switches in the upward position
- Factory default configuration
- Enters standby after approximately one hour without signal
- Standby consumption approximately 0.4 W
Automatic Standby Disabled
- Both standby switches in the downward position
- Unit remains operating until switched manually
- May be preferred in some systems
- Increases energy consumption
Positioning and Reducing Hum
Moving-coil cartridge signals are extremely small and can be affected by electromagnetic fields from nearby equipment.
Position the Aos MC as far from the turntable as the tonearm cable reasonably allows.
Keep it away from power amplifiers, large transformers, mains distribution blocks, wireless routers and motor power supplies where possible.
Avoid stacking other Hi-Fi components directly above or below the Aos MC.
Keep turntable signal cables away from mains leads and speaker cables. Where the cables must cross, arranging them at approximately a right angle may help reduce induced hum.
If low-level noise remains intrusive, try the lower gain setting and move the phono stage further from possible electrical interference.
Ventilation and Installation
Place the Aos MC on a strong, stable and level equipment shelf.
Rega recommends maintaining at least 10 cm of open space around the product for ventilation.
Do not place the unit on thick carpet, fabric or another soft surface that could restrict airflow.
The mains socket should remain easily accessible because the mains lead also acts as the disconnection device.
Retain the original packaging in case the product needs to be returned for inspection or servicing.
Fono MC, Aos MC or Aura?
Rega Fono MC Mk4
The
Rega Fono MC Mk4
is the most affordable dedicated Rega moving-coil phono stage.
- Compact case
- External 24 V power supply
- Four resistance settings
- Two capacitance settings
- Two gain settings
- Natural partner for Ania and Ania Pro
Rega Aos MC
- Aura-derived two-stage circuit
- Symmetrical Class A amplification
- Internal mains power supply
- Full aluminium half-width enclosure
- Automatic standby
- Natural partner for Ania Pro and Apheta 3
Rega Aura Reference MC
The
Rega Aura Reference MC
is Rega's flagship moving-coil phono stage.
- Three-stage symmetrical circuit
- More resistance and capacitance settings
- Balanced and unbalanced outputs
- Front-panel gain, mute and mono controls
- Substantial reference power supply
- Natural partner for Apheta 3 and Aphelion 2
The most appropriate phono stage depends on the cartridge, turntable, amplifier and overall resolution of the system. A direct demonstration is the best way to establish whether the Aos or Aura provides a worthwhile improvement.
What the Rega Aos MC Does Not Include
No Moving Magnet Input
- Moving-coil input only
- No 47 kO moving magnet setting
- Not suitable for Rega Carbon or Nd cartridges
- Use a compatible MM stage instead
No Digital Connections
- No USB input or output
- No optical connection
- No coaxial digital connection
- No analogue-to-digital conversion
- No computer recording interface
No Balanced Connections
- Stereo RCA input
- Stereo RCA output
- No balanced XLR input
- No balanced XLR output
No Volume or Headphone Control
- Not a conventional pre-amplifier
- No listening-volume adjustment
- No headphone socket
- Requires a line input on an amplifier or pre-amplifier
No Front Loading Controls
- Loading is selected on the rear panel
- Settings should be changed with the unit switched off
- No front-panel mute switch
- No front-panel mono switch
No Remote or App Control
- No remote handset
- No network connection
- No Bluetooth
- No application
- Automatic standby can be configured manually
Who Is the Rega Aos MC For?
A Good Choice If You:
- Use a conventional low-output moving-coil cartridge
- Own a Rega Ania Pro, Apheta 3 or Aphelion 2
- Want a substantial upgrade from the Rega Fono MC Mk4
- Want Aura-derived circuit technology in a smaller case
- Need adjustable resistance, capacitance and gain
- Want an internal mains power supply
- Prefer a purely analogue signal path
- Need automatic standby
- Own a Planar 6, Planar 8, Planar 10 or Naia
- Want a phono stage that can remain as the cartridge is upgraded
Consider Another Option If You:
- Use a moving magnet cartridge
- Use a high-output moving coil designed for an MM input
- Need balanced XLR outputs
- Want front-panel loading controls
- Need a mono or mute switch
- Want USB recording or digital outputs
- Need a headphone amplifier or volume control
- Want the full reference performance and flexibility of the Aura
- Need a smaller and more affordable phono stage
Key Features
- Dedicated low-output moving-coil phono stage
- Designed and assembled in the UK
- Circuit based heavily on the Rega Aura Reference MC
- Two-stage all-analogue amplifier
- Symmetrical complementary Class A first stage
- Linear Systems ultra-low-noise FET transistors
- Carefully graded and matched input devices
- Compound FET input-pair arrangement
- No bias current through the cartridge coil
- No input coupling component between cartridge and FET stage
- Passive high-frequency RIAA equalisation
- Symmetrical Class A differential second stage
- Common-base driver stage
- Active low-frequency RIAA equalisation
- Self-adjusting temperature-compensation servo
- Four selectable resistance settings
- 70 O, 100 O, 150 O and 400 O loading
- Two selectable capacitance settings
- 1000 pF and 4300 pF capacitance
- Two selectable gain settings
- 69 dB and 63 dB gain
- Factory configured for all Rega moving-coil cartridges
- Stereo RCA input
- Stereo RCA output
- Separate turntable earth terminal
- Automatic standby after approximately one hour
- User-defeatable automatic standby
- Custom aluminium half-width case
- Internal mains power supply
- Rega mains lead supplied
- Lifetime limited warranty against confirmed manufacturing defects
Included Accessories
- Rega Aos MC Phono Stage
- Rega mains lead
- User documentation
A separate stereo RCA interconnect is required between the Aos MC output and the amplifier unless a suitable cable is already available.
Frequently Asked Questions
What does the Rega Aos MC do?
It amplifies the extremely low-level signal from a moving-coil cartridge and applies the required RIAA equalisation before passing the signal to a normal amplifier line input.
Is the Aos MC suitable for moving magnet cartridges?
No. Moving magnet cartridges require a dedicated moving magnet stage such as the Rega Fono MM Mk5.
Can it be used with a high-output moving-coil cartridge?
Some high-output moving-coil cartridges are designed for a moving magnet input rather than a high-gain MC stage. Check the cartridge manufacturer's recommendation before connection.
Which Rega cartridges are compatible?
The factory settings are suitable for the Rega Ania, Ania Pro, Apheta 3 and Aphelion 2.
What are the Rega factory settings?
Rega configures the Aos MC for 100 O resistance, 1000 pF capacitance and 69 dB high gain.
Can it be used with third-party cartridges?
Yes. It can be used with many conventional low-output moving-coil cartridges whose gain and loading requirements fall within the available settings.
Which resistance settings are available?
The available input resistance values are 70 O, 100 O, 150 O and 400 O.
Which capacitance settings are available?
The Aos MC provides 1000 pF and 4300 pF settings.
How much gain does it provide?
The two gain settings are 69 dB and 63 dB at 1 kHz.
Should I always use high gain?
No. Use the gain appropriate for the cartridge output. Excessive gain can reduce headroom and increase the audibility of background noise.
Can the settings be changed while it is operating?
No. Switch off the Aos MC and amplifier before changing the loading or gain switches.
Where does the turntable connect?
Connect the turntable's RCA plugs to the input sockets on the rear of the Aos MC.
Where does the Aos MC output connect?
Connect it to a normal amplifier line input marked AUX, CD, Line, Tuner or similar.
Can it connect to the Phono or MC input on my amplifier?
No. The Aos MC is already a complete phono stage. Its output must connect to a conventional line input.
Can I use it if my amplifier already has a phono stage?
Yes. Connect the Aos MC to a spare line input and compare it with the amplifier's internal moving-coil stage.
Do I need to use the earth terminal?
Use it if the turntable or tonearm has a separate earth wire. Rega tonearms normally earth through the signal cable and do not require one.
What should I do if the system hums?
Check the RCA plugs, earth connection, cable routing and distance from nearby mains supplies, motors and amplifier transformers.
Which component should be switched on first?
Rega recommends switching on the Aos MC before the amplifier. When switching off, turn off the amplifier before the Aos MC.
Does it have automatic standby?
Yes. It enters standby after approximately one hour without an input signal.
Can automatic standby be disabled?
Yes. Move both rear standby switches to their downward positions. Disabling standby increases power consumption.
Does it contain digital circuitry?
The signal amplification and loading controls are purely analogue. There is no USB connection, digital audio processing or analogue-to-digital conversion.
Does it have balanced XLR outputs?
No. The Aos MC uses stereo RCA input and output connections.
Does it have a mute or mono switch?
No. These front-panel functions are available on the higher-level Rega Aura Reference MC.
Does it have a headphone output?
No. Headphones must connect to the amplifier, pre-amplifier or a separate headphone amplifier.
Is an output interconnect included?
A stereo RCA output cable is not listed among the standard accessories, so a suitable interconnect is normally required.
Should I choose the Fono MC, Aos MC or Aura?
The Fono MC is the most affordable option, the Aos adds more sophisticated Aura-derived circuitry and an internal power supply, while the Aura is Rega's full reference phono stage. A demonstration is the best way to establish the right level for your system.
Can Audio T configure the Aos MC for my cartridge?
Yes. Provide the cartridge make and model and our store teams can check the recommended resistance, capacitance and gain settings.
Why Buy From Audio T?
- Specialist moving-coil cartridge and phono-stage advice
- Help confirming cartridge output and loading requirements
- Rear DIP-switch configuration support
- Demonstrations with Rega Ania Pro, Apheta 3 and Aphelion 2 cartridges
- Comparisons with the Rega Fono MC Mk4 and Aura Reference MC
- Planar 6, Planar 8, Planar 10 and Naia system matching
- Turntable setup, cartridge alignment and tracking-force guidance
- Advice on earthing, cable routing and reducing hum
- Help matching the phono stage to your amplifier and wider system
- Home demonstrations may be available depending on location and system requirements
- Part exchange available on suitable equipment
- Ongoing support from the UK's oldest independent specialist Hi-Fi retailer
Contact your local Audio T store
to arrange a demonstration or discuss the correct Aos MC settings for your moving-coil cartridge.