Musical Fidelity Fx: Power Amplifier

The FX is built on a robust steel chassis with a distinctive Musical Fidelity aesthetic: a plain black or silver front panel with a single blue (or sometimes red) LED indicator. The rear panel features:

Internally, the PCB is laid out for short signal paths, with careful grounding to avoid hum loops. Components are through-hole (typical of the era), making the amplifier relatively serviceable today.

This amplifier is a masterclass in "right-sizing" your system. musical fidelity fx power amplifier

Ideal User 1: The Desktop Connoisseur You have a DAC (like a Schiit Modius or Topping E70) that acts as your volume control. You sit 3 feet from speakers like the Vanatoo or Elac Uni-Fi. The FX sits on your desk, driving near-field monitors with zero fan noise and high-end warmth.

Ideal User 2: The Second System Builder You have a big, expensive main rig in the basement. You need something for the bedroom or office. You pair the FX with a Wiim Pro Plus streamer (which has a basic volume control) and some vintage bookshelf speakers. Total cost: under $500. Total enjoyment: Priceless. The FX is built on a robust steel

Ideal User 3: The Vinyl Purist You own the Musical Fidelity FX-LPS phono preamp. You want a direct, signal-path-short chain: Turntable -> FX-LPS -> FX Power Amp -> Speakers. No tone controls, no digital conversion. Just pure analog gain.

| Component | Specification | |-----------|----------------| | Output stage | Complementary bipolar (e.g., 4 pairs of Sanken MT-200 per channel) | | Bias sensing | Microcontroller (STM32) reading: input signal envelope, heat sink thermistors (<0.5°C resolution), output current via Hall sensor | | Bias control | Digitally controlled variable current source feeding Vbe multiplier | | Modes | Low bias (25 mA idle) – 50W Class-AB; Medium bias (200 mA) – first 5W Class-A; High bias (1.2A) – first 35W Class-A | Internally, the PCB is laid out for short

Transition logic:

When enthusiasts search for the Musical Fidelity FX Power Amplifier, they are usually referring to one of three specific models, though the design philosophy is identical across the board.