Audio T Verdict
The Sugden Masterclass PA-4 is a serious phono amplifier designed for vinyl systems using moving-magnet, moving-coil or multiple cartridges.
It provides two dedicated moving-coil inputs and a separate moving-magnet input, allowing compatible turntables or tonearm and cartridge combinations to remain connected. Standard MC loading options of 100 and 470 ohms are provided, while Sugden can factory-configure the amplifier to match the requirements of a particular cartridge.
Separate Class A circuits are used for the MM and MC stages, supported by a carefully regulated current-shunt power supply. The PA-4 is an excellent choice for listeners who want a flexible, purpose-built analogue front end without digital processing or unnecessary features.
Sugden Masterclass PA-4 Phono Amplifier
The Sugden Masterclass PA-4 is a handmade British phono amplifier designed to extract the low-level musical signal produced by a turntable cartridge.
It provides dedicated amplification and RIAA equalisation for both moving-magnet and moving-coil cartridges, raising their output to a level suitable for connection to a conventional line input on an integrated amplifier or preamplifier.
The PA-4 combines three cartridge inputs, two line-level outputs and factory-configurable loading with separate Class A circuit designs optimised for MM and MC operation.
Designed for Serious Vinyl Systems
A phono cartridge produces a much lower output than a conventional CD player, streamer or DAC. Its signal also requires specific equalisation to reverse the frequency curve applied when a record is cut.
The PA-4 performs both tasks within a dedicated component, providing the gain and RIAA correction required before the signal reaches the main amplifier.
Separating the phono stage from an integrated amplifier also gives Sugden greater freedom to optimise the circuit, power supply and cartridge-loading arrangements specifically for vinyl reproduction.
Three Dedicated Cartridge Inputs
The PA-4 provides three stereo phono inputs:
- Moving-coil input MC1
- Moving-coil input MC2
- Moving-magnet input MM
The required input can be selected from the front panel, allowing compatible turntables, tonearms or cartridge combinations to remain connected.
This can be particularly useful in a system containing more than one turntable, a turntable with multiple tonearms or a removable-headshell arrangement using different cartridges.
Two Moving-Coil Inputs
Two dedicated inputs are provided for compatible moving-coil cartridges.
Sugden publishes an MC input sensitivity of 0.15mV, making the PA-4 suitable for many low-output moving-coil designs.
Moving-coil cartridges vary considerably in output voltage, internal impedance and recommended loading, so compatibility should always be confirmed before connection.
Dedicated Moving-Magnet Input
A separate moving-magnet input is provided with a published sensitivity of 3.5mV.
The MM input uses the conventional 47k-ohm loading specified by Sugden and is suitable for many established moving-magnet cartridge designs.
Some high-output moving-coil cartridges may also be compatible with an MM input, although their output and recommended loading should be checked individually.
100 and 470-Ohm MC Loading
Sugden publishes moving-coil loading options of 100 and 470 ohms.
Cartridge loading influences the electrical relationship between the moving-coil cartridge and phono amplifier. Different load values can affect tonal balance, high-frequency behaviour, dynamics and perceived openness.
The correct setting should be selected using the cartridge manufacturer’s recommendations as a starting point, followed by careful listening where appropriate.
Check Cartridge Compatibility
Moving-coil cartridges do not all require the same input impedance.
Before connecting a cartridge, check its output voltage and recommended load against the PA-4’s sensitivity and loading configuration.
Contact your local Audio T store for help matching your cartridge to the PA-4.
Factory-Configured Cartridge Loading
In addition to its published loading options, Sugden states that the PA-4 can be factory-set to match the requirements of a specific cartridge.
This allows the electrical loading to be tailored more closely when a cartridge requires a value other than the standard 100 or 470 ohms.
The required cartridge model and manufacturer specifications should be confirmed before ordering a custom-configured unit.
Factory Loading Is Not a Front-Panel Adjustment
The front-panel controls select between MC1, MC2 and MM. Sugden does not describe the PA-4 as having a continuously adjustable front-panel loading control.
Any non-standard cartridge matching should therefore be discussed with Audio T before the amplifier is ordered.
Class A Moving-Coil Stage
The moving-coil section uses a Class A current-feedback amplifier circuit.
Class A operation keeps the active devices continuously conducting, avoiding the switching between operating states found in some alternative amplifier designs.
The current-feedback arrangement has been selected specifically for the extremely low-level signal generated by a moving-coil cartridge.
Class A Moving-Magnet Stage
The moving-magnet section uses a separate Class A voltage-feedback circuit.
This allows the MM stage to be optimised around the higher output voltage and different electrical requirements of a moving-magnet cartridge rather than simply applying additional gain to the MC circuit.
Providing dedicated MM and MC topologies allows each cartridge type to be handled by an appropriate amplifier design.
RIAA Equalisation in the Feedback Loop
The moving-magnet amplifier incorporates RIAA correction within its negative-feedback loop.
RIAA equalisation restores the frequency balance altered during the record-cutting process. Without it, vinyl playback would sound thin, quiet and severely lacking in bass.
Sugden publishes a frequency response accuracy of ±0.3dB between 10Hz and 30kHz.
Direct-Coupled Moving-Coil Signal Path
DC servo circuits allow the musical signal to remain directly coupled from the moving-coil input through to the PA-4’s final output.
This avoids the need for conventional coupling capacitors at several points within the MC signal path.
The servo circuit controls unwanted DC conditions while allowing the low-level audio signal to pass through the amplifier stages directly.
Current-Shunt Power Supply
Sugden considers the power supply to be an integral part of the PA-4’s amplifier circuitry.
The unit uses a current-shunt power-supply design together with a specially developed voltage regulator.
The regulator is intended to prevent the supply impedance from rising as frequency increases, helping the phono circuit remain stable while responding to fast changes within the music signal.
Gold-Plated Circuit Boards
The PA-4 is assembled using gold-plated circuit boards selected for long-term stability.
High-quality components are hand fitted and assembled as part of Sugden’s traditional British manufacturing process.
The amplifier is designed and produced at Sugden’s factory in Heckmondwike, West Yorkshire.
Two Line-Level Outputs
Two line-level outputs are provided for connection to compatible analogue equipment.
The selected and amplified cartridge signal is available at line level, allowing the PA-4 to be connected to a normal auxiliary, line, CD, tuner or similarly labelled input on an integrated amplifier or preamplifier.
Sugden publishes an output level of 360mV under its stated test conditions.
Use a Line-Level Amplifier Input
Connect the PA-4’s output to a conventional line input on your amplifier.
Do not connect it to another phono input. Passing the signal through two phono stages would apply excessive gain and RIAA equalisation twice, causing severe distortion and incorrect tonal balance.
Front-Panel Input Selection
The front panel provides direct selection between MC1, MC2 and MM.
An input indicator confirms which cartridge input is currently active.
This arrangement allows different connected record-playing sources to be selected without moving cables behind the system.
Standby Control
A standby control is provided on the front panel.
This allows the PA-4’s operating state to be controlled without using a rear-mounted mains switch during normal listening.
Sugden does not list remote-control operation for the PA-4.
System Positioning
Phono cartridge signals are extremely small and can be affected by electrical noise, mains transformers and poorly routed cables.
Place the PA-4 on a stable equipment support and avoid positioning it directly beside or on top of components containing large power transformers where practical.
Keep phono cables away from mains leads and power supplies, and avoid coiling excess signal cable beside mains equipment.
Turntable Earthing
Turntable earthing arrangements vary between manufacturers and models.
Follow the instructions supplied with the turntable, tonearm and cartridge. If a separate earth lead is provided, connect it to the appropriate grounding point specified for the system.
An incorrect or incomplete earth connection can cause audible hum, while creating unnecessary additional earth paths can also introduce noise.
Compact Masterclass Casework
The PA-4 measures 430mm wide, 110mm high and 330mm deep.
Its full-width casework matches other products within Sugden’s Masterclass range while remaining easier to accommodate than the company’s larger power amplifiers.
Sugden publishes a gross packed weight of 6kg.
Key Features
- Dedicated MM and MC phono amplifier
- Part of the Sugden Masterclass range
- Handmade in Heckmondwike, West Yorkshire
- Two dedicated moving-coil inputs
- One dedicated moving-magnet input
- Front-panel MC1, MC2 and MM selection
- Front-panel input indicator
- Front-panel standby control
- Class A current-feedback moving-coil stage
- Class A voltage-feedback moving-magnet stage
- RIAA correction within the MM negative-feedback loop
- DC servo-controlled moving-coil circuit
- Direct-coupled MC signal path
- Current-shunt power supply
- Specially designed voltage regulator
- Gold-plated circuit boards
- High-quality internal components
- Moving-magnet sensitivity of 3.5mV
- Moving-coil sensitivity of 0.15mV
- 47k-ohm moving-magnet loading
- 100 and 470-ohm moving-coil loading
- Factory-configurable cartridge loading
- Two line-level outputs
- 360mV published output
- 10Hz to 30kHz frequency response, ±0.3dB
- Greater than 70dB signal-to-noise ratio
Frequently Asked Questions
What is the Sugden PA-4?
It is a dedicated phono amplifier that provides the gain and RIAA equalisation required to connect compatible turntable cartridges to a conventional line-level amplifier input.
Does the PA-4 support moving-magnet cartridges?
Yes. It provides one dedicated MM input with 3.5mV sensitivity and 47k-ohm loading.
Does it support moving-coil cartridges?
Yes. It provides two dedicated MC inputs with a published input sensitivity of 0.15mV.
How many turntables can be connected?
The PA-4 provides three stereo cartridge inputs: two moving-coil and one moving-magnet. This can accommodate up to three compatible phono sources.
Can I connect two moving-coil cartridges?
Yes. Separate MC1 and MC2 inputs are provided.
Can I switch between MM and MC from the front panel?
Yes. Front-panel controls select MC1, MC2 or MM, with an indicator showing the active input.
Which moving-coil load settings are available?
Sugden publishes standard moving-coil loading values of 100 and 470 ohms.
Can the MC loading be matched to another value?
Sugden states that the PA-4 can be factory-set to match a cartridge exactly. Non-standard loading requirements should be confirmed when ordering.
Is the loading continuously adjustable from the front panel?
No continuously adjustable loading control is listed. Factory configuration should be discussed before purchase when a cartridge requires a non-standard value.
What is the moving-magnet input sensitivity?
Sugden publishes an MM input sensitivity of 3.5mV.
What is the moving-coil input sensitivity?
Sugden publishes an MC input sensitivity of 0.15mV.
Will it work with every moving-coil cartridge?
Not necessarily. Cartridge output, internal impedance and recommended loading must be checked for compatibility.
Can a high-output moving-coil cartridge be used?
Potentially, but the cartridge output and recommended loading should be checked to determine whether the MM or MC input is the better match.
Are the MM and MC circuits the same?
No. The MC stage uses a Class A current-feedback circuit, while the MM stage uses a Class A voltage-feedback circuit.
Does the PA-4 use RIAA equalisation?
Yes. The MM amplifier incorporates RIAA correction within its negative-feedback loop.
Is the moving-coil signal path directly coupled?
Yes. Sugden uses DC servo circuits to allow direct coupling from the MC input to the final output.
What type of power supply does it use?
It uses a current-shunt power supply with a specially designed voltage regulator.
How many outputs are provided?
Two line-level outputs are listed.
Can both line outputs be used simultaneously?
Sugden’s published product information does not confirm whether there are any restrictions on simultaneous use. Check with Audio T if this is required for your system.
Which amplifier input should I use?
Connect the PA-4 to a normal line-level input such as AUX, CD, tuner or line.
Should I connect it to another phono input?
No. The PA-4’s output has already been amplified and equalised, so it should be connected to a line-level input.
Does the PA-4 have balanced outputs?
Sugden lists two line-level outputs but does not specify balanced outputs.
Does it include remote control?
No remote-control facility is listed. Input and standby controls are located on the front panel.
What is the published output level?
Sugden publishes an output of 360mV.
What is the frequency response?
Sugden publishes a frequency response of 10Hz to 30kHz within ±0.3dB.
What is the signal-to-noise ratio?
Sugden publishes a signal-to-noise ratio greater than 70dB.
Where is the PA-4 manufactured?
It is handmade at Sugden’s factory in Heckmondwike, West Yorkshire.
How large is the Sugden PA-4?
It measures 430mm wide, 110mm high and 330mm deep.
How much does the PA-4 weigh?
Sugden publishes a gross packed weight of 6kg.
Related Products and Audio T Guides
Why Buy From Audio T?
- Independent advice from experienced Hi-Fi specialists
- Moving-magnet and moving-coil cartridge matching
- Help selecting the correct cartridge loading
- Factory-loading enquiries for compatible cartridges
- Turntable, tonearm and cartridge setup assistance
- Cartridge alignment and tracking-force adjustment
- Advice on phono earthing and system noise
- In-store demonstrations at participating branches
- Cable and equipment-support recommendations
- Home demonstrations and product loans where available
- Click and Reserve from participating stores
- Nationwide UK delivery on eligible products
- Ongoing after-sales support
Contact your local Audio T store to discuss matching the Sugden Masterclass PA-4 to your turntable, cartridge and amplifier.