Aune Audio S17 Pro EVO Headphone Amplifier

The Aune S17 Pro EVO is a fully discrete, fully balanced Class A headphone amplifier that delivers up to 7.5 watts into 32 ohms with a measured noise floor of about 3.6 microvolts. Those two numbers are the story in miniature: enough power for the most demanding planar magnetic headphones made, and a background quiet enough for sensitive in-ear monitors.

The S17 Pro EVO is the amplifier half of a serious desktop system. There is no DAC inside, by design: connect any DAC or streamer through RCA or balanced XLR and it handles everything downstream, driving headphones from three front-panel outputs or acting as the preamp for powered speakers. It replaces the S17 Pro at the top of Aune's amplifier line, keeping the same Class A circuit and adding the usability the original lacked.

Class A, and Why It Runs Warm

Class A means the output transistors conduct at full current all the time, whether music is playing or not. Because the transistors never switch off, the design avoids crossover distortion entirely and stays in its most linear operating region at every volume. The sound this topology is known for is warm, smooth, and dense, with low-level detail that stays refined as the level climbs.

Constant current means constant heat, and the S17 Pro EVO manages it honestly. Two selectable current modes set the character: A-L runs 100mA per channel for everyday listening, while A-H doubles it to 200mA for maximum current reserve and the fullest presentation. Heatsinks, a bottom heat plate, and the chassis itself form one integrated cooling structure vented through the rear panel, and if the internal temperature reaches 69C the amplifier steps itself back to A-L automatically. It is built to run warm; give it some breathing room and it will hold stable Class A operation all day.

Twin JFETs In, 16 Transistors Out

Aune builds the input stage around matched twin JFET transistors. JFETs combine very high input impedance with a naturally smooth transfer characteristic, which is why their sound is so often compared to vacuum tubes. Using two thermally matched devices keeps the circuit's midpoint voltage stable as the amplifier warms up, so the tube-like richness stays consistent from cold start to hour three.

The output stage uses two parallel pairs of transistors per channel, 16 output transistors in total across the balanced circuit, fed by a 50 watt low-ripple toroidal transformer and a 19,200uF capacitor bank. Power for the digital control circuitry is kept separate from the analog supply so the audio path stays free of interference. The measured result is 0.00024% THD+N at 1kHz, vanishingly low distortion for a high-current Class A design.

Power for the Hardest Headphones on the Wall

Inefficient planar magnetic headphones like the HIFIMAN Susvara are the reason amplifiers like this exist. The S17 Pro EVO delivers 7,500mW into 32 ohms and nearly 3 watts into 90 ohms from its balanced outputs, real current reserves for headphones that starve on smaller desktop amps. High-impedance dynamics are covered too: 908mW into 300 ohms is far more than a Sennheiser HD 800 S will ever ask for. You can check your own headphones against these numbers with our headphone power calculator.

Two gain levels make that power usable across the whole range. Low gain pairs finer volume steps with the roughly 3.6uV noise floor so IEMs and efficient headphones stay hiss-free, while high gain opens up the full 7.5 watts. Headphones connect through 4-pin XLR balanced, 4.4mm balanced, or 6.35mm single-ended outputs on the front panel.

Volume You Can Trust at Whisper Levels

Volume is handled by a four-way balanced R2R resistor network built around a JRC volume chip with dedicated op-amps. Unlike a conventional potentiometer, which drifts out of balance at the bottom of its range, the R2R control keeps left and right channels matched at exactly the low levels where late-night listening happens, and it preserves staging and image placement while doing it.

Day-to-day control is simple: one multifunction knob adjusts volume, gain, and current mode, and a 4-inch display shows input, gain, mode, volume, and internal temperature at a glance. The interface shifts between blue for A-L and red for A-H so you always know how hard the amp is running, an automatic screen-off option keeps the desk dark, and the all-aluminum remote handles everything from the couch.

A Preamp When the Headphones Come Off

The S17 Pro EVO doubles as a proper analog preamp. Headphone and preamp operation are selected independently, and each mode remembers its own volume setting, so switching from headphones to powered speakers does not start with a lunge for the knob. Balanced XLR and RCA preamp outputs feed active monitors or a power amplifier, and two line inputs let a balanced DAC and a second source stay connected at once.

In an all-Aune stack it is the natural partner for the AR9000 flagship open-back, with the balanced power and Class A control to show what that 50mm carbon fiber driver can do. It fits just as naturally under any DAC you already own.

What EVO Changes, and What It Keeps

Compared with the original S17 Pro, the EVO adds the operational polish the platform deserved: independent switching between headphone and preamp output, separately stored volume for each mode, and the automatic screen-off function. The component count rises from 635 to 657, while the fully discrete Class A architecture, twin JFET input, and 7.5 watt balanced output stage carry over intact.

At $799, the S17 Pro EVO makes a simple case: genuine high-current Class A sound, enough clean power for any headphone in the store, and preamp flexibility that lets one box anchor both your headphone and speaker listening.

Key Features

• Fully discrete, fully balanced Class A headphone amplifier and preamp
• Up to 7.5W balanced output into 32 ohms
• Matched twin JFET input stage for a smooth, tube-like character
• 16 output transistors, two parallel pairs per channel
• Selectable Class A current: A-L 100mA or A-H 200mA per channel
• Automatic step-down from A-H to A-L at 69C for thermal protection
• Four-way balanced R2R volume control with precise low-level channel matching
• Two gain levels covering sensitive IEMs to demanding planars
• Approx. 3.6uV output noise in high gain; 0.00024% THD+N
• 4-pin XLR, 4.4mm balanced, and 6.35mm headphone outputs
• Balanced XLR and RCA inputs; XLR and RCA preamp outputs
• Independent headphone and preamp modes with separate volume memory
• 50W low-ripple toroidal transformer with 19,200uF capacitor array
• Integrated three-dimensional cooling structure for stable Class A operation
• 4-inch color display with two-color current-mode UI and temperature readout
• Multifunction knob and all-aluminum remote control
• Hi-Res Audio certification

Technical Specs

Headphone Output Power