description

Musical Fidelity A1 Integrated Amplifier

A 25 Wpc pure class-A with sliding bias based on a near-perfect 1985 circuit design but with better power supplies and components. Also with MM/MC phonostage and remote control.

First released in 1985, the Musical Fidelity A1 made waves for being an absolute beast when it came down to driving some of the most difficult speakers of that time, even though it was actually a rather low-powered integrated amplifier. The magic came from its pure class-A design and expertly laid out discrete symmetrical circuitry topology and using only highest quality components. 

Based on its huge success, the A1 has gone through multiple reissues and new versions over the years.

Now for 2023, Musical Fidelity has preserved the specifications, appearance, and circuits of the 1985 rendition for those who missed out the first time. Inside, though, it has been updated with new transformer, power supplies, and modern low-noise components

Pure Class A 

The A1 is built around a completely discrete and symmetrical Class A topology, offering 25 Wpc with 25 A of maximum output. Fans of class-A designs will know that 25 W is a lot of power, and when needed for hard-to-drive speakers, it slides into class-B operation

The new A1 has a dual mono split rail transformer. The amp stages are supplied by fully independent left and right power supplies for better power handling and stereo imaging and each power amplifier now has double supply capacity resulting in reduced ripple and noise.

The transformer‘s noise and heat dissipation are reduced due to better efficiency and updated components. The main supplies are filtered for better regulation and reduced switch-on surge.

Small-Signal Wins

The low noise preamplifier circuitry is the same as the excellent original 1985 design but greatly benefits from the improved, fully smoothed, and regulated power supplies. A "direct" switch bypasses the pre-gain before the attenuator, allowing for more knob travel with high-level digital sources, or for sensitive speakers.

The volume potentiometer is a premium ALPS RK series, a high-quality component that ensures superior performance and enhanced precision. And, in a usability upgrade since 1985, the volume pot is motorized, allowing for the use of the new remote control.

The A1 has a discrete current-mode phonostage for moving coil and moving magnet cartridges. A low noise current to voltage conversion stage is used for further amplification and RIAA equalization. Automatic input impedance matching for the selected MC input, along with increased gain increases the versatility of the A1‘s phonostage.