Power amplifiers stereo — Sugden Audio SAPPHIRE FBA-800

The Sapphire FBA-800 is a pure Class A stereo power amplifier from Sugden Audio, built with a distinctive Floating Bridge design combining four 20-watt Class A amplifiers within a single stereo chassis. Sugden Audio has been designing and manufacturing amplifiers in West Yorkshire, England for 59 years, and the FBA-800 is described by the brand as its most advanced power amplifier to date, drawing on decades of accumulated Class A expertise.

Key specs that matter

Balanced XLR and phono/asymmetric RCA inputs are both provided as stereo pairs, with front-panel push-button input selection and an optional -6dB sensitivity reduction step for matching balance across a specific amplifier chain. Input sensitivity is 735mV for full output. Power output is 40W per channel into 8 ohms with both channels working, delivered through the floating bridge architecture where each channel uses two voltage amplifiers driving bridged output transistors with the output earth floating - this distinctive topology delivers a lower noise floor, effectively double the power output relative to the voltage rails, and better load tolerance thanks to fixed Class A current. Frequency response is 0dB across 20Hz-80kHz, with bandwidth extending to 6Hz-113kHz at -3dB. Signal-to-noise exceeds 96dB, with distortion under 0.05% at 1W, 1kHz. Four multi-emitter power transistors per channel each deliver up to 26 amps. The power supply uses a single custom-made bifilar-wound transformer with four separate windings, feeding smoothing capacitors specially developed for professional audio applications. At 206 x 430 x 460mm and 25kg, construction uses gold-plated circuit boards and high-quality internal silver wiring, with through-hole rather than surface-mount components specifically chosen to enhance long-term life and reliability.

Sound and use context

Expect immense resolution and soundstage with genuine quickness and "aliveness" in the overall presentation - one reviewer specifically noted the FBA-800 effortlessly drove five different loudspeakers spanning very different efficiencies and impedance loads, from Rosso Fiorentino and Tekton Design to Sonus Faber, without strain.

Pairing

The dual balanced and single-ended input pairs with switchable sensitivity give genuine flexibility matching this amplifier to a wide range of preamplifiers, and the amplifier's tolerance for varied impedances suits both efficient and more demanding loudspeaker designs.

Alternatives

Sugden Audio's broader Class A amplifier catalogue, including integrated models drawing on the same core engineering philosophy, offers alternatives for buyers wanting Sugden's characteristic sound in a different configuration, worth comparing directly with a dealer given the considerable investment this flagship power amplifier represents.