Musical Fidelity A1 stereo amplifier

Musical fidelity A1

In the world of Hi-Fi, the Musical Fidelity A1 is one of the most iconic amplifiers – both internally and externally. First released in 1985, the A1 quickly attracted attention for its incredible ability to drive the most demanding loudspeakers of its time, despite being a relatively low-power integrated amplifier. However, its secret lay in its pure Class A operation, carefully designed symmetrical discrete amplifier circuitry and high-quality components. The A1 proved that amplifiers are about more than just power.

Due to its success, A1 has received several re-releases and new versions over the years.

Now in 2023, for the first time since the original release, we have fully preserved the specifications, appearance and circuitry of the 1985 version for those who missed it the first time around. With an updated transformer, power supplies and modern low-noise components, we have brought this classic back to life and are proud to present the original, fresh and revamped – three decades later.

MUSICAL FIDELITY A1 EISA 2024-2025 Enthusiastic Amplifier

The jury writes the following:

"Musical Fidelity's A1 integrated amplifier takes music lovers back in time, reviving the signature slim body and much of the internals of the company's original model launched in the 1980s. This amplifier remains fully analogue, with an MM/MC turntable connection, line inputs and tape loop connection, but now benefits from carefully designed upgrades to the power supply and internal cooling. It also features a welcome Direct mode that bypasses the preamp gain.

Otherwise, this 2x25W Class A amplifier continues where its predecessor left off – known for its organic, almost tube-like soundstage that brings out music in an excitingly expansive and expressive way."

Technical details

The A1 is built around a fully discrete and symmetrical Class A topology. It is capable of delivering 25W of pure Class A power into an 8 ohm load and has a maximum current draw of 25A. While these figures may seem small, its ability to drive demanding loudspeakers is a minor miracle in itself. The amplifier's dynamic Class A design means that if the Class A quiescent current is exceeded, it automatically allows more current. It therefore "slips" (NOT "switches") smoothly into Class B-type operation, allowing for a temporary higher current draw.

Power supply

The new A1 features an updated transformer, moving from the original (1985) split design to a more efficient “dual mono split rail” coil. The amplifier stages are provided with fully independent left and right channel power supplies, improving power handling and stereo imaging. In addition, each power amplifier now has double the input capacity, reducing interference and noise.

Transformer noise and heat generation have been reduced thanks to improved efficiency and upgraded components. The main power supplies have been filtered for better regulation and lower inrush current.

Preamplifier

The low-noise preamplifier circuit remains the same as the original 1985 model and benefits from significantly improved, fully rectified and regulated power supplies.

One of the notable changes is the addition of a new "direct" switch to the preamplifier stage. This allows you to completely bypass the gain stage before adjusting the volume, reducing the gain by approximately 10 dB. This feature is particularly useful when using modern or high-output digital audio sources, as it allows for fine-tuning of the volume control and is suitable for use with sensitive speakers.

Additionally, a significant upgrade has been made to the volume potentiometer itself, which has now been replaced with a top-quality ALPS RK series potentiometer. This high-quality component ensures excellent performance and even more precise adjustment. In addition, the potentiometer is now motorized, allowing you to adjust the volume from the comfort of your couch using the included remote control.

Turntable preamplifier

The A1 uses a discrete current-mode input stage for the lowest possible noise amplification of MC and MM cartridges. In addition, a low-noise current-to-voltage conversion stage provides further amplification and RIAA correction. Automatic input impedance matching for the selected MC input and added gain enhance the versatility of the A1 turntable preamplifier.

A true Hi-Fi classic returns

The A1 has one secret. This secret is simple: it brings music to life. Its sound is smooth and soft, creating a beautiful atmosphere around natural instruments. Especially in small and medium-sized rooms, carefully placed together with high-quality two-way speakers, it shines. It is not a power hog, but music lovers will appreciate its unique abilities.

It's also not a product you'd want to hide. A perfect example of form following function. The oversized cooling fins are not only the A1's recognizable look, but they're also essential to its functionality. Truly unique, inside and out.

The A1's sound is sweet, warm, rich and exhilarating. No harshness. No graininess. Just pure music. It doesn't crackle, and despite its lower power, it drives demanding speakers effortlessly. It stays clean right up to the power limit. To hear what the A1 does is to hear what Hi-Fi should do: it simply plays music – cleanly and clearly.

A1 over time – Improvements to the original

• Updated transformer for more efficient "dual mono split rail" winding

• High-quality and updated ALPS RK series potentiometer as volume control

• IR remote control added for volume control

• Gain block before volume control completely bypassable with "direct" switch (-10 dB)

• All transistors, including the output stage components, are carefully selected modern equivalents

• All capacitors in the signal path are polypropylene (PP) type

• The resistors are modern, low-noise metal film resistors

• Care has been taken to ensure that the technical values ​​of the components have not been changed, but have been updated to modern, long-lasting versions.

• The circuit board faithfully follows the original wiring diagram in terms of circuit assemblies

• Circuit layout optimized especially for separate power supplies and power amplifiers

• Turntable preamp and preamplifier improved to reduce noise and hum

A1 Summary

• 25W of pure Class A power @ 8 Ohm

• Discrete symmetric topology

• Planar Audio transistors with 25A maximum output

• Dynamic Class A, smoothly slides (NOT switches) into Class B mode, allowing for more power when needed

• So let's take difficult speakers with ease

• Updated transformer to "dual mono split rail" coils

• Fully independent left and right power supplies

• Each power amplifier now with double the power supply capacity

• Transformer noise and heat dissipation reduced

• Filtered main power supplies

• Gain block before volume control completely bypassable with "direct" switch

• High quality and updated ALPS RK series potentiometer

• Low Noise TL071 JFET Preamplifier Circuit

• Discrete power-mode MM/MC turntable connection

• Low noise current-to-voltage converter for extra volume and RIAA equalization

• Automatic input impedance adjustment (1K nominal) for MC with additional gain

• Original (1985) A1 appearance and circuitry with modern improvements

• Remote control added for volume

• Modern, updated low-noise components

Specifications:

Amplifier

• Power: 25 watts per channel into 8 Ohms

• Voltage: 42.5 volts peak to peak

• Current: 25 amps peak to peak

• Damping factor: 150

• Volume gain (maximum): 32dB (Direct mode), 42dB (Normal mode)

• Output components: 2 per channel

• Signal to noise ratio: 82dB

• Channel separation: 85dB

• Frequency response: +0, –1dB, 10Hz – 40kHz

• Line level sensitivity: 300mV rms nominal, 8V rms maximum

• Line level input impedance: 25k Ohm

• Tape output impedance: 220 Ohm

• Pre-out impedance: 100 Ohm

Turntable preamplifier

• Phono RIAA response: +/- 1dB

• MM sensitivity: 5mV nominal

• MM capacitance / impedance / gain: 100pF / 50k Ohm / 40dB

• MM signal to noise ratio: 75dB

• MC sensitivity: 450µV nominal

• MC impedance/gain: 1k Ohm/60dB

• MC signal to noise ratio: 70dB

Revenue

• 1x phono RCA MM/MC

• 5x line input RCA

Departures

• 1x line output RCA fixed TAPE OUT

• 1x line output RCA adjustable PRE OUT

• 1x 4mm banana/mounting posts SPEAKER OUTPUT

General information

• Dimensions (WxHxD): 440 x 68.3 x 283.3 mm

• Mains voltages: 230V/115V internally set or 100V optional

• Maximum consumption: 130W, 0W in standby mode (=Power switch off)

• Weight: 10.5 kg