FIIO EA13 Class-A tube amplifier delivers 28W per channel

The FIIO EA13 is a pure Class-A push-pull vacuum tube power amplifier built around two SYLVANIA NOS PCF80 voltage-amplification tubes and four JJ ELECTRONIC EL34 power tubes. It delivers up to 28W + 28W into either 4Ω or 8Ω speaker loads, with dedicated transformer taps for each impedance, while a 6.35mm headphone output supports headphones from 16Ω to 300Ω. Four RCA analog inputs, custom EI output transformers, a 40-step analog volume control, mechanical VU meters, and 12V trigger control make the EA13 suitable for conventional speaker systems as well as multi-source desktop and full-size HiFi systems.

Six-tube Class-A push-pull circuit

The EA13 uses a pentode-mode, pure Class-A push-pull topology derived from established tube-amplifier circuit principles. Two SYLVANIA NOS PCF80 tubes handle voltage amplification, while four Czech-made JJ ELECTRONIC EL34 tubes form the power-output stage.

Speaker output reaches 28W + 28W into either 4Ω or 8Ω with THD+N below 5%. At a stricter THD+N threshold below 1%, rated output is at least 18W + 18W. Separate 4Ω and 8Ω binding-post connections allow the output transformer to operate with speaker loads matched to the appropriate secondary winding.

Custom EI output transformers

The output stage feeds custom EI silicon-steel transformers designed for wide bandwidth and low noise. In a tube amplifier, the output transformer provides the impedance conversion required to couple the high-voltage, relatively high-impedance tube output stage to low-impedance loudspeakers.

Each transformer is filled internally with epoxy resin and fine sand before being sealed inside a protective enclosure. The construction is intended to suppress mechanical vibration while adding electromagnetic shielding and protection against moisture.

40-step precision analog attenuation

Volume is controlled through a 40-position high-precision analog potentiometer using matched precision resistors at each increment. The stepped arrangement maintains more consistent left-to-right channel tracking across the adjustment range than a conventional continuously variable carbon-film potentiometer, particularly at lower volume settings where channel mismatch can become more apparent.

The resistor-based construction also reduces reliance on a conventional carbon-film contact track, addressing the channel-balance variation and mechanical wear that can develop in standard analog volume controls over extended use.

Power-supply and signal-path components

FIIO uses axial metal-film coupling capacitors in the EA13 signal path, selected for low loss, low distortion, and stable electrical characteristics. Large-capacity Japanese NCC filter electrolytic capacitors are used in the power-supply section to smooth the supply rails and reduce residual power-supply noise reaching the amplification circuitry.

The amplifier is housed in a unibody chassis with a CNC-machined aviation-grade aluminum front panel. The enclosure adds structural rigidity and electromagnetic shielding, while recessed tube mounting, an integrated protective cover, side ventilation grilles, and vibration-damping feet support heat management and stable operation around the exposed tube stage.

Four analog inputs and dedicated speaker taps

Four RCA line-level inputs allow the EA13 to accept sources including DACs, CD players, streamers, and turntables connected through a suitable external phono stage. A four-position front-panel selector provides direct mechanical input selection.

Gold-plated binding posts provide dedicated 4Ω and 8Ω speaker outputs, while the front-panel 6.35mm headphone connection supports headphones rated from 16Ω to 300Ω. A 12V Trigger In port allows power control to be synchronized with compatible upstream components in a multi-component system.

Mechanical VU meters and front-panel control

Dual mechanical VU meters display the left- and right-channel signal levels using needles driven by the incoming music signal. Warm LED backlighting is controlled by a dedicated IC, retaining the behavior of an analog meter while separating illumination control from the audio signal path.

The left front-panel control also manages knob illumination and VU-meter lighting through single- and double-press commands. Adjustable RGB illumination around the two control knobs can be configured to suit the surrounding system or switched off entirely.

Automatic low-power standby

A precision signal-detection circuit monitors the selected input during operation. If no input signal is detected for 30 minutes, the EA13 automatically enters a low-power standby state, reducing energy consumption and limiting unnecessary operating time on the vacuum tubes.

Availability

The FIIO EA13 is available now at apos.audio.