FiiO CLASS A Fully Discrete Class A Desktop Headphone Amplifier & Preamplifier

The FiiO CLASS A is a fully discrete Class A transistor headphone amplifier and preamplifier, and the heart of FiiO’s retro-style desktop hi-fi system. Built from individually selected audio transistors, resistors and capacitors, matched for each channel and tuned by hand, it recreates a pure, warm, natural and distinctly analogue sound, with up to 4,000mW per channel into 32Ω balanced from a custom 60W toroidal transformer and a 20,000µF capacitor reservoir. Five gain levels and independent bass and treble controls let you tailor it to any headphones.

Two transistor types, one union

FiiO pairs two types of audio transistor. Toshiba complementary pairs and twin transistors bring warmth and smoothness, a relaxed low end and sweet, engaging vocals; Sanken audio transistors add precision, speed, incisive dynamics and strong control, for composure and authority with large-scale orchestral and rock music. The quiescent current of every unit is calibrated by hand.

Carefully selected audio components

Eight WIMA film capacitors, twenty ELNA audio capacitors and twenty high-precision MELF resistors give the CLASS A exceptional resolution with a warm, engaging musical character, so it performs superbly yet stays easy to listen to for hours.

A split power supply with 20,000µF in reserve

A split power-supply design gives the amplification stages their own independent regulated power. The 20,000µF of Nichicon audio filter capacitors smooth the current after rectification and store energy for sudden peaks, suppressing mains ripple for a deep, black background. When drums or a full orchestra hit, they release that energy quickly, so the dynamics stay controlled and the bass tight and powerful.

A custom 60W toroidal transformer

Built for the high quiescent current a Class A amplifier needs, the transformer is wound through several complex processes for efficient, low-interference, clean power. A continuous silicon-steel strip core gives high magnetic flux density and low losses, all-copper enamelled windings give low internal resistance and high current, copper foil between the primary and secondary windings and an outer silicon-steel shield reduce interference, and a built-in resettable thermal switch protects against overheating.

Fully balanced, with a DC servo

The fully balanced differential circuit gives strong interference rejection, low distortion, a spacious soundstage and plenty of drive: up to 4,000mW + 4,000mW into 32Ω from the balanced outputs. A high-precision DC servo continuously monitors the output and corrects any DC offset, keeping it at zero. That protects your headphones and improves the bass and transparency, for clearer sound and better low-frequency control.

Five gain levels and tone controls

Low, medium, high, super high and ultra high gain make it easy to find the right setting for each pair of headphones, from efficient models to demanding full-size designs. Independent bass and treble knobs, each with up to ±10dB, add low-frequency weight or treble clarity without software EQ.

Connections for a whole system

Four inputs (3.5mm and RCA single-ended, 4.4mm and XLR balanced) take any analogue source. Headphones plug into 6.35mm, 4.4mm balanced or 4-pin XLR outputs, and RCA and XLR line outputs feed a power amplifier or active speakers, with the CLASS A as a preamp. A bidirectional 12V trigger (in and out) switches your whole system on and off together, and a USB-C port is for firmware updates.

Protection for your amplifier and headphones

Built-in protection monitors the CLASS A in real time and steps in automatically: DC output protection, power-input overcurrent protection, headphone-amplifier temperature protection, overvoltage protection, output overload detection and transformer thermal protection.

FiiO’s retro desktop hi-fi system

FiiO designed its desktop system with one size and design language from source to DAC to headphone amplifier, so components match without effort: for example, the DP11 CD player, the WARMER R2R tube DAC and the CLASS A.

Good to know

• The CLASS A is an amplifier only, with no DAC: connect a DAC or other analogue source, such as the FiiO K11 R2R from its RCA line outputs.
• In the box: CLASS A, AC power cord, RCA cable, quick start guide, warranty card, dust cap and spare fuse.