Musical Fidelity Fx: Power Amplifier

Modern Class D amplifiers now boast 90% efficiency and 0.0001% distortion, yet many listeners still hunt for the FX. Why? Because the FX reminds us that high fidelity is not a number. It is the illusion of a live performance. By sacrificing power for purity, and features for focus, Musical Fidelity created an amplifier that does not just reproduce music—it understands the importance of the first watt.

However, the FX has a fatal flaw for the careless user: it demands sympathetic partners. With 50 watts, it is useless on power-hungry electrostatic speakers or large floor-standers with impedance dips below 4 ohms. But pair it with high-efficiency (90dB+) stand-mount monitors—a classic Spendor, a Harbeth, or an old pair of Klipsch Heresy—and the FX becomes a window, not a wall. In 2024, the Musical Fidelity FX is a cult classic, frequently changing hands on the used market for a fraction of its original price. It serves as a philosophical totem for a specific kind of audiophile: one who values musical engagement over specifications. musical fidelity fx power amplifier

The FX is, in fact, a "Class A" amplifier for the first critical 10 to 15 watts. Only when pushed harder does it slide gracefully into Class B. This is not a marketing gimmick; it is a sonic philosophy. By keeping the output devices constantly biased “on,” the FX eliminates crossover distortion—the tiny notch of discontinuity that occurs when transistors switch on and off. This grants the amplifier an almost tube-like liquidity in the midrange, but with the grip and speed of solid-state. Open the lid of an FX, and a minimalist gasps with joy; a maximalist weeps. Where other amplifiers looked like circuit boards suffering from acne—covered in capacitors, relays, and protection circuits—the FX is spartan. Its signal path is vanishingly short. Modern Class D amplifiers now boast 90% efficiency and 0

In the high-fidelity industry, there is an unspoken hierarchy of glamour. Turntables have the romance of mechanical precision; tube amplifiers glow with nostalgic warmth; and loudspeakers, with their exotic drivers and wooden veneers, are the furniture of dreams. The power amplifier, by contrast, is often treated as the mule of the system—ugly, utilitarian, and expected only to deliver current without complaint. It is the illusion of a live performance

Musical Fidelity employed a fetishistically simple dual-mono design. Two toroidal transformers (one for each channel) sit at the front, isolated from a remarkably small number of gain stages. There are no tone controls, no headphone jacks, no "processor loops." This is a machine with a single purpose: to amplify the input signal without adding or subtracting anything but amplitude.