Musical Fidelity A1 - Class-A Integrated Amplifier

The Musical Fidelity A1 Integrated Amplifier is a piece of hi-fi history. First produced in the 1980s, its pure Class A electrical design was famous not just for its ability to work with a wide variety of equipment of the day, but for its ability to deliver a sound performance like nothing else. The new generation of A1, released in 2023, stays true to the original design in almost every way, only making changes to improve certain technical characteristics and suit modern requirements.

Class-A and Class-B Topology

The electrical layout of the A1 features completely discrete, fully symmetrical pure Class A technology. Delivering 25W of power (to an 8Ω load), it can also handle 25A of maximum current output. Though these numbers may seem low compared to some modern amplifiers, the A1 is still able to drive more complex speakers thanks to its ability to slide (not “switch”) into Class B operation when further current draw is temporarily needed.

Re-designed Power Supply

The A1’s transformer design is directly inspired by the 1988 design but has been updated with more efficient dual-mono split-rail windings and better components for improved stability and better heat management. The amplifier stages are now powered by fully independent supplies for left and right channel allowing for better power handling and stereo imaging. Each power amplifier also now has double the supply capacity, resulting in reduced ripple and noise artefacts.

Pre-Amplification Stage

The low-noise pre-amplifier circuitry is the same as the original A1, though this area also benefits from new modern touches. First, the DIRECT switch on the front panel allows users to bypass the Gain stage before the musical signal reaches the volume dial. By switching this button on, the pre-amplifier stage will apply roughly 10dB less gain, suiting it to more modern, high-gain source devices that may benefit from a wider volume dial range.

Second, the use of a new ALPS RK series motorised potentiometer for the volume dial not only allows greater accuracy and reliability, but it means the 2023 A1 amplifier can also make use of a remote control for volume adjustments.

Built-In Phono Stage

Alongside five RCA stereo inputs, a fixed level output and a variable output, the A1 also features a high-quality built-in phono stage. The phono input allows for direct connection to a turntable, whether it has a moving magnet (MM) or a moving coil (MC) cartridge. The low-noise design and automatic impedance-matching for MC cartridges make this a viable solution, and a great convenience for vinyl record lovers.

Chassis Construction

The industrial design of the A1 is the same as the original from the 1980s, with its angular front panel, full-length top-mounted heatsink and side-mounted ventilation panels. The only minor modifications are intended to help enhance the user experience and manage the heat output from the pure Class A technology employed within. The result, when combined with the intricate workings, is an amplifier that takes you right back to the original design brief for the A1: to enjoy music.

Technical Specifications

Amplifier Section

• Power: 25 Watts per channel into 8 Ohms
• Voltage: 42.5 Volts peak to peak
• Current: 25 Amps peak to peak
• Damping Factor: 150
• Gain (volume max): 32dB (Direct Mode), 42dB (Normal Mode)
• Output devices: 2 per channel
• Signal / noise ratio: 82dB
• Channel separation: 85dB
• Frequency response: + 0, –1dB, 10Hz to 40 kHz
• Line level sensitivity: 300mV rms nominal, 8V rms max
• Line level inputs impedance: 25k Ohms
• Tape Out impedance: 220 Ohms
• Pre Out impedance: 100 Ohms

Phono Preamp

• Phono RIAA response: +/- 1dB
• MM sensitivity: 5mV nominal
• MM capacitance / impedance / gain: 100pF / 50k Ohms / 40dB
• MM signal / noise ratio: 75dB
• MC sensitivity: 450μV nominal
• MC impedance / gain: 1k Ohm / 60dB
• MC signal / noise ratio: 70dB

Inputs / Outputs

• 1 x phono RCA MM/MC, 5x line RCA
• 1 x line level RCA fix TAPE OUT
• 1 x line level RCA var PRE OUT
• 1 x 4mm banana/binding posts SPEAKER OUT

General Information

• Dimensions (WxHxD): 440 x 68.3 x 283.3 mm
• Main voltages: 230V/115V Internally set or 100V optional
• Max. Consumption: 130W, 0W in standby (=Power Switch OFF)
• Weight: 10.5kg

Further Information

Musical Fidelity A1 - User Manual (PDF)