Aune S17 Pro Review

The Aune S17 Pro review sample was kindly provided free of charge in exchange for an honest review. I didn’t receive monetary or any other kind of compensation and I don’t use affiliate links. The price of the Aune S17 Pro is $699 and you can buy it either from the official Aune store or Amazon USA or your local distributors.

Aune Audio

Aune Audio is a well established brand that has been devoted to developing desktop and portable audio products such as DACs, digital transports, music players, headphone amplifiers and earphones. They are committed to the pursuit of superb sound and great user experience while at the same time keeping their prices as friendly as possible. The brand has been extensively covered by ichos-reviews where you can read reviews for most of their highly acclaimed products like the AUNE X1s GT, X8 XVIII, Flamingo and Aune S9c Pro or even the Jasper.

Aune S17 Pro Review 

The Aune S17 Pro is a fully discrete, pure Class A, fully balanced headphone amplifier. It uses twin JFET, a transistor that has high input impedance and is distinguished by its rich and mellow sound like a vacuum tube thus making it the ideal input transistor for a headphone amp. The S17 Pro final output stage uses two pairs of output transistors per phase in parallel arrangement. The whole device has as many as 16 output transistors reaching a 7.5W per channel of maximum power output.

Additionally, the S17 Pro uses an R2R electronic volume chip from JRC and dedicated op-amps to build a 64 steps, 4-way balanced R2R volume control for high control precision and great channel balance.

The S17 Pro is equipped with a high quality linear power supply built around a 50W low-ripple toroidal transformer and a total of 19200uF of rectifying capacitance. It is a dual-power design where digital control and analog sections are independent from each other, so the analog part can be free from interference.

The components used for the S17 Pro are only high-quality ones that are carefully selected, such as HiFi electrolytic capacitors, ceramic capacitors, organic thin-film capacitors, communication-grade PCB etc, all from well known and established brands.

Two levels of quiescent current

The Aune S17 Pro has a specially designed feature that allows the user to select between two levels of quiescent current. You can either select 50mA or 100mA per transistor and as each channel of the S17 Pro has two pairs of transistors in parallel, the actual quiescent current of each channel is as high as 100mA or 200mA respectively.

In Class A working mode, the amplifiers output transistors remain conducting all the time, whether there’s an input signal or not. They have their currents equal to the AC peak and the maximum AC signals flow to the load so the open-loop distortion is extremely low, therefore it is regarded as the ideal amplifying circuit design.

The drawback of Class A is the considerably increased power consumption and intense heat generation but this is something that the Aune S17 Pro can handle without issues thanks to the complex cooler structure that includes specially designed heat-sinks.

Let’s talk about temperature

The Aune S17 Pro has a unique feature that constantly measures the temperature of the amplifier at the heat-sinks and displays it in the lower right corner of the LCD display. The embedded auto protection circuit will auto switch the bias current from 100mA to 50mA when the temperature reaches 69⁰C.

Thermal stability of the output transistors is essential for the optimal performance of the Aune S17 Pro and the best sound quality. Upon powering the amplifier the temperature will be equal to the environmental one, like 22⁰C, and then it will slowly rise. It needs about half an hour to stabilize at about 45⁰C for the 50mA bias and 55⁰C for the 100mA. After this point the temperature will remain almost stable and will further rise only when you start playing music.

The amplifier is ready to perform at its best only after the temperature is stabilized to the above values so it is highly recommended to power it on and wait at least half an hour before you start listening to music.

Appearance and build quality

The S17 Pro features the Aune’s trademark ark design with the curved top surface that is beautiful, yet classic and minimalistic, looking but it has the disadvantage of leaving visible gaps at the sides when you place two similar devices, the one at the top of the other.

The chassis is entirely made from CNC machined aluminum that effectively shields the amplifier from EMI. It has a smooth finish which is available in silver and black. The multifunctional knob is also made from aluminum and has a nice working feeling without wobble. There is really nothing else to note other than that the Aune is a luxurious looking and extremely well made product with an overall quality that far exceeds its price.

The front panel is plain and simplistic, the LCD display is positioned at the center, the headphone outputs at the left side and the multifunction knob at the right. At the back there are the line inputs and outputs, both available in XLR and RCA plugs, the AC mains input and the power switch.

Connectivity and operation

The Aune S17 Pro is both a headphone amplifier and a preamplifier with three headphone outputs (4-pin XLR, 4.4mm and 6.35mm) and a pair of line level inputs/outputs (XLR and RCA).

You can control the device with the multifunctional knob or the supplied remote control which is slim and made from aluminum. The large LCD screen displays all the useful information at once and has excellent visibility but the colors are somewhat washed out, especially the red one that lits when you enable the 100mA bias operation. Additionally there is no option to dim or switch it off.

The available functions are to select XLR or RCA line inputs, set the gain to high or low and select bias current.

The preamplifier output is always active and doesn’t mute when you plug the headphones. The volume control is always active for both outputs so someone must be careful not to fry his headphones. Additionally this is not very practical when you frequently switch between headphones or active monitors.

Power output and associated gear

The Aune S17 Pro is really powerful as it can provide 2W/32Ω and 7.5W/32Ω from its single ended and balanced outputs respectively. It is also very effective in driving higher Z loads as it can supply 900mW/300Ω from the balanced output. To get a rough idea about the power reserves of the Aune S17 Pro, with the Focal Clear Mg I never exceeded 30-35 in the low gain and with the notoriously difficult to drive HIFIMAN Susvara, 55 at the high gain was more than enough to drive them at their full potential. BTW, the S17 Pro is an excellent sonic match with the HIFIMAN Susvara, an absolutely fantastic sounding combination.

The output impedance is 1Ω for both outputs thus making the amplifier also suitable for driving low Z, sensitive earphones, especially if we consider that the background noise is barely audible, something miraculous for such a beast. There is always the risk of getting loud too early with some very efficient loads but then again I don’t see many of you buying this amplifier for running such earphones. 

The Aune S17 Pro scales incredibly well and will reward you if you mate it with a high quality source. I started with the Aune X8 and S9c Pro but eventually I ended up using the, four times more expensive, Lab 12 dac1 reference. All headphone and power cables are made by Lavricables.

Traditionalists vs modernists

Readers familiar with my previous Aune reviews will know that this is a brand that I greatly admire because they have departed from the latest “Chi-Fi” trend which values absolute scientific measurements more than actual music realism. Various brands that design audio devices without much inspiration with their only aim to make them measure better and better but in the end they tend to sound more or less the same, lifeless and sterile.

Instead, Aune Audio follows more traditional “HiFi” methods with a painstaking tuning made by the ear and by carefully testing and hand picking the right audio components, among hundreds of them, until the final product meets their needs for the most realistic sound, despite the subjectivity of such a decision.

Listening impressions

The Aune S17 Pro is a great example of an audio component that is tuned like a real instrument. A device made for playing actual music rather than merely reproducing sounds to end sounding clinical and sterile. You don’t have to listen a lot in order to realize how effortlessly the music is flowing from this excellent sounding amplifier. Pure music, full of emotions and deep engagement that bonds the listener and never lets him go. An addicting amplifier that is going to consume all of your free time but thankfully for a good reason, for feeding your soul and brain with exhilarating music.

Stellar sound quality that combines excellent technicalities and transparency with the most natural timbre. Timbre is the keyword for describing the audio performance of the Aune S17 Pro. This is a headphone amplifier with an extremely analogue and organic timbre that makes music to sound as lifelike as possible, especially when combined with high quality sources and headphones, like the Meze Elite. Yes, the $4K Meze Elite, that good is the $700 Aune S17 Pro, a mid-priced amplifier that can do full justice to high-end sources and headphones.

The sound is rich, full and harmonious from the lowest octave to the highest treble. The frequency response is actually linear with an extended bass that is weighty, visceral and impactful. It has great dynamic contrast and excellent control, it sounds fast but not hurried, well defined and layered with plenty of clarity and resolution.

The mid-range is sweet and organic with an unbelievable realism that is usually achieved only with vacuum tubes. It is warm but not mellow, nor dark, veiled or hazy sounding. This is a well designed solid state amplifier that offers a great dose of magic without lacking in clarity, resolution and definition. Instruments and voices are reproduced with a lifelike manner, they are full sounding with a solid harmonic foundation and plenty of colorful overtones. The mid-range feels robust and well articulated, spacious and refined, it plays well with all kinds of music but especially with everything that involves acoustic instruments and human voices.

The treble is full bodied, smooth and polite but without lacking in extension and clarity. Energetic but not nervous, luminous but not too brilliant, this is the kind of treble that is never going to sound harsh or fatiguing even after endless hours of listening. It is pure and realistic without a single trace of artificiality or digital ringing and with the most natural and effortless decay. Detail retrieval is excellent, the amplifier can reveal all the hidden nuances of the recording but it knows when to stop in order to avoid sounding analytical or mechanical.

The soundstage is wide and spacious with great positioning accuracy and plenty of depth layering but nothing really better than other competing amplifiers. However the greatest strength of the Aune S17 Pro is that it sounds grand, immersive and holographic, with large, well sculptured images that can reach out of the listeners head.

The Aune S17 Pro pairs well with all kinds of sources and headphones and while there are no limits when it comes to music selection, it is absolutely phenomenal with classical music.

50mA vs 100mA

These two modes will not yield dramatically different sound signatures but mostly subtle variations on the same theme. 50mA offers slightly faster transients and the sound is a bit cleaner but in 100mA it becomes more diffuse and naturally flowing with a greater sense of realism and musicality. Your mileage may vary and the outcome is also headphone and source dependent.

Preamplifier

The Aune S17 Pro has an excellent preamplifier output that retains all the sound qualities as described above. It is suitable for use with active monitors but also a great option for driving stereo power amplifiers with the added easiness of the remote control.

Compared to the Violectric V222 (€1199)

The Violectric V222 is a solid state amplifier made by a company that shares the same way of thinking with Aune Audio as they also design and painstakingly fine-tune their products to make them sound as realistic as possible.

The Violectric V222 is one of my favorite solid state headphone amplifiers because it combines excellent technicalities with a very natural timbre. The V222 is a mildly warm sounding amplifier with a sound character that reminds a lot of vacuum tubes so imagine my surprise when I found that the Aune S17 Pro is more “tubey” and warmer sounding than the V222.

Comparing the two of them yielded some key differences in their sound characteristics despite them sharing the same audio philosophy. In short, the Violectric V222 is cleaner sounding with somewhat better transparency and more openness. It is more impactful and dynamic, definitely faster and hits harder but it has a leaner, drier texture so it is not as visceral and full sounding as the Aune S17 Pro.

The Violectric V222 has faster transient response and a slightly sharper, more energetic treble with a touch of extra luminosity. It is still a smooth and fatigue free sounding amplifier but comparably, it sounds more aggressive than the Aune S17 Pro which is more polite and smoother on the treble.

Both offer plenty of emotional depth and engagement while they share the same kind of timbre realism but the Aune S17 Pro is just a touch more organic and analogue sounding with more colorful and varied harmonies.

A final difference has to do with the soundstage which is wider, more open and spacious with better positioning accuracy in the V222 while it places the listener a half step closer to the center of the stage. The Aune S17 Pro might be a bit narrower and less accurate but it manages to sound grander and more holographic.

The Violectric V222 is still my favorite solid state headphone amplifier but now I must confess that half of my heart belongs to the Aune S17 Pro.

In the end

Simply put, the Aune S17 Pro is a hell of a surprise, this is a headphone amplifier that combines all the technical competency that a modern solid state amplifier should have with tones of musicality and realism. Amazing sound that is going to make your headphones shine and let your music flow as never before.

And don’t let the price fool you, the Aune S17 Pro is one of the best solid state headphone amplifiers your money can buy and can only be bettered by rivals costing at least two and three times more. Actually it can easily rank as an end-game amplifier, no matter how expensive your sources and headphones are. A miraculous achievement by Aune Audio that points to a brilliant future but also raises a high quality bar that will need plenty of hard work in order to get surpassed.

Test playlist

Copyright – Petros Laskis 2023.

+ Stellar sound quality
+ Excellent technicalities
+ Musical and natural timbre
+ Smooth and fatigue free
+ Complete absence of artificiality
+ Grand and holographic
+ Super powerful
+ Temperature monitoring
+ Barely audible noise floor
+ High quality preamplifier
+ Multi connectivity
+ Large LCD display
+ Excellent build quality
+ Remote control

- Can't mute the volume
- LCD display can't be dimmed or switched OFF
- Gets warm during use
- Line output is always active and will not mute when you plug your headphones 
- Too much power for sensitive loads