Aune S6 PRO review - a Maestro in disciple clothes

Overall Score 92/100
Sandu Vitalie Sources

Disclaimer: Aune S6 PRO was sent to us free of charge in exchange for our honest opinion. We thank team Aune Audio for this opportunity.

My video review is right here:

At München High-End Show 2019 that was held just few days ago Aune Audio unveiled few updated audio components, to us the most interesting ones were the S6 PRO High-performance DAC and headphone amp combo and the S7 PRO balanced headphone amp. Both are currently their flagships in a desktop-fi environment where headphone listening is crucial.

We will be testing their quite interesting S6 PRO DAC and headphone amp combo as a DAC alone and as a combo with two balanced headphones and few IEMs.

S6 PRO is an updated version to their older S6 design, both look basically the same except the PRO badge on the newest device.

So, what exactly was changed and improved?

  • S6 used an AKM 4495S DAC chip, S6 PRO is using a much more advanced AKM 4497EQ chip for a higher dynamic range and SNR.
  • S6 was doing DSD128 only via USB, S6 PRO can decode DSD512
  • S6 offered 72 mW into 300 Ohms, S6 PRO has 120 mW on the SE headphone out, on balanced S6 has 246 mW and S6 PRO offers a much beefier 405 mW into 300 Ohms!

Probably the biggest improvement is in the headphone amp section where power output almost doubled on both SE and 4-pin XLR balanced headphone output.

I suspect improvements were made on the volume wheel as well; volume wise newest device is offering a very convenient 100 digital steps.

Inside the box

Unboxing experience was really good, S6 PRO came double boxed with lots of foam for extra protection.

Inside the smaller black box you’ll find: the S6 PRO, a high quality USB cable, a power cable, a 6.35 mm to 3.5 mm (1/4” to 1/8”) headphone adapter, a user manual, a business card, an USB Flash drive that contains the drivers, the user manual and a photo gallery - basically everything you need to start your listening session. S6 PRO comes in two variants: in a beautiful white case or in a black case. I think it looks better in white as it looks somehow more premium this way.

Design & Build Quality

Fit and finish is excellent and it looks stunning too. It is on the bigger and heavier side compared to other DAC/Amp units we had in the past for review, as such it is quite imposing and left a great initial impression on us.

The aluminum case is quite thick, it looks sandblasted to absorb scratches and accidental drops, so far it looks very well put together with great tolerance numbers. On the bottom there are four rubber feet to absorb micro-vibrations. The front panel is very clean and houses a big and beautiful LCD screen, a 4-pin XLR balanced headphone out, a SE 6.35mm (1/4”) headphone out and a digital volume knob that has few tricks under its sleeve. Pressing once the knob will change the digital input, pressing twice will change the output (HP out or Line-Out) and a long 5-sec press will turn it Off or On.

That big and really easy to read LCD screen will show important information as the selected digital input, the analog output, the material it is being played (PCM or DSD), the bitrate and the volume level.

On the back there is an AC Power in, a power switch, 4 digital inputs! (USB, Optical, Coaxial and AES) and two clean line-outs: a SE RCA out and a balanced XLR output. Since both line-outs can be volume controlled, S6 PRO can be used as a digital preamp as well.

Some might find the shape a little odd, since the top is slightly rounded, if you want to put something on top of it, say the S7 PRO you will need deeper feet, at least 1.5cm (0.6”) long to avoid the curvature or scratching the surface. I’m fine with it as it looks quite unique, I didn’t encounter nothing like it so far.

Tech Specs & Detailed information

Aune Audio did the right thing choosing the best AKM chip for their most advanced offering of the moment, S6 PRO is using the venerable AK4497EQ DAC Chip in detriment of an older but still good AK4495S. AK4497EQ is part of the Verita Velvet Sound architecture for a very natural sound performance and fatigue-free listening experience.

The USB input is handled by a high-performance XMOS (2-nd generation) interface for a very low-noise and low-distortion performance.

Headphone amplification is handled by two TPA 6120A2 chips, this is a stereo chip, so just one is needed for a single ended HP out and two for a true balanced HP out. Japan made Nexem relays are everywhere, WIMA capacitors, as well as Nichion audio grade electrolytic capacitors – that is a really good sign. For a clean power delivery Aune opted for a high-quality toroidal transformer, we love this one.

S6 PRO is using a low noise clock system and multiple sets of low noise power supplies to have everything in check.

On the USB input S6 PRO will decode PCM material up to 32 bit / 768 kHz and up to DSD512. THD is a very low 0.0005% with an impressive channel crosstalk of -132dB! The line-outs are following the international standard of 2 Vrms on RCA and 4 Vrms on XLR.

Headphone amplifier will deliver up to 405mW in 300 Ohms on balanced and 120mW on single ended, that is enough for majority of headphones but not really enough for hard to drive headphones, we encountered only two cases when our headphones under-performed on two high dynamic tracks.

S6 PRO doesn’t have a gain switch, but I didn’t feel the need for one as first 50 digital volume steps worked wonderful with our very sensitive In-Ear-Monitors (IEMs for short) and the rest 50 steps worked nice with the bigger and hungrier headphones.

Sound Performance

I. Using S6 PRO as a DAC/headphone amp combo is a desktop setup

A. Using S6 PRO with sensitive In-Ear-Monitors

There is a saying in the audiophile circles that still comes to my mind sometimes:

Q: What is high-end audio? A: You’ll know it when you hear it!

When I listen to the S6 PRO to some degree this is true, everything just clicks into place when I am listening to it. It has the perfect dose of naturalness and technical prowess and will impress both types of audiophiles: tech specs freaks or techno-philes as I call them and just normal music lovers that care only about sound and I am honestly thinking S6 PRO will please both camps.

I plugged in my very sensitive FiiO FA7 and FH7, pushed volume to max setting and was awestruck to find out that it has the lowest noise and blackest background I ever heard in a pair of super-sensitive IEMs. This means it just bested my reference Gilmore Lite MK2, the Burson Playmate, the Loxjie D20 and even FiiO’s own very high performance THX AAA module!

Seriously, for IEM users S6 PRO is a dream come true, any other desktop DAC or DAC/Amp I have tested until now has higher noise floor and a bit of hum, S6 PRO is free of any of that! Even battery powered amps have more noise than this…Aune is quoting me an uber-low 2.3 uV noise and a total harmonic distortion of just 0.0005% and I am believing them, seeing is believing as they say.

Listening to S6 Pro made me think it has an exact dose of naturalness and precision, an excellent tonal balance across the board. On my favorite tracks it never appeared as boring and dry sounding, on the contrary it always sounded true to life with impressive dynamics with great speed and impact carrying a quite linear frequency response.

I fired up Queen – The Prophet’s Song and jumped to min 3:30 (please do the same) and was mesmerized by the impressive play with my imagination, musical notes would just jump left to right and back, closing my eyes I just transported myself into a binaural world, an incredible performance thanks to the S6 PRO. There is just a single drawback of this song, it has a DR 13 rating - it means it was recorded at -20 dB and for harder to drive headphones you could be maxxed out even on the balanced output.

A close friend visited me, he plays drums as a hobby and uses custom made IEMs when he plays, he asked what is this beautiful white box on the table, I explained everything and invited for a listen, he sat down and fired a song by SOAD and maaan I remember just the look on his face. Words were simply unnecessary as the joy, the wide smile on his face and the headbanging were enough for me to know what he is feeling. He told in the end that he never experienced SOAD like this, so natural, so visceral and hard hitting. I think I just converted a normal man into an audiophile, poor man, he doesn’t know the dangerous perils of this journey yet 😊

I resumed my listening with few tracks from Pink Martini and could just swear that I upgraded soundstage levels of my headphones, it sounded much more decompressed, wider that usual and especially deep. That deepness was almost eerie as my IEMs never sounded as open and deep, I don’t want to sound overly positive, but for IEM users I didn’t find a flaw, nothing!

B. Using S6 PRO with full-sized headphones (Balanced and SE)

My favorite headphones at the moment are the amazing and really affordable Quad ERA-1 headphones, the fun factor with these is unbeatable, I’m sure about that.

I’m very fond of some local folk-rock bands that are blending rock jams with folk instruments in such an interesting way, I can please both of my fetishes at the same time.

I connected the Quad ERA-1 to the balanced XLR output and resumed my listening and I had the same feeling of a very impressive depth, layering and soundstage to a degree that I started questioning if my home reference DAC (the Matrix X-Sabre Pro – a 1800 USD DAC only device) can do the same and to the Matrix shame and to my surprise S6 PRO sounded deeper with incredible pin-point imaging. Soundstage wise both sounded on the same level, very wide and expanded in all directions. This is the biggest compliment I can give to Aune Audio, a 600 USD device playing in the same ball park as a 1800 USD device is not something that can be said on a daily basis.

So far, in terms of pin point imaging and depth S6 PRO is very, I mean very impressive.

There is also something interesting going on, like very small dynamic swings that move just a tiny bit of air and I do not mean micro-details, it’s something else that ESS Sabre designs are not doing properly. On just few tracks I felt that more air is hitting my eardrums in places never occurred on my own DAC, those weren’t new sounds or tiny details, just air bubbles hitting my eardrums here in there, so far this is my first feeling of this type. Impressive is not the right word here, I’m a bit speechless.

S6 PRO had an impressive flow and most of the time sounded so effortlessly that I wanted to open it again and search for a vacuum tube or for a R-2R Non-Oversampling DAC chip inside hidden somewhere.

In my previous review (Loxjie D20) I felt almost the same level of easiness, great flow and naturalness but S6 PRO is offering that at a much higher degree. S6 Pro is also not suffering from weak transients and slam that D20 is having.

I will discuss the entire frequency area listening to speakers but want to add that with headphones S6 PRO offers an incredible slam especially in the bass area and moves air like a very high-performance headphone amp is doing.

In absolute terms comparing to the best out there, S6 PRO headphone amp section can still be improved. There were very few occasions when even on the balanced headphone out with my planar-magnetics I was still craving for just a higher volume, otherwise there is nothing to complaint about its HP out.

At 100% volume it doesn’t clip, doesn’t distort and it is as clean as at 1% volume, from IEMs to full-sized headphones, I’m already imaging myself how much better the S7 PRO must be?! We shall find about that at a later date.

In balanced mode S6 PRO is clearly pumping more power and is offering a wider volume range for harder to drive headphones. In Single Ended mode it worked best with IEMs and only OK-ish with big cans. If you are a serious headphone listener, go with the balanced connection, it is just much better in terms of power and dynamics.

II. Using S6 PRO as a DAC only in my stereo setup

My active KEF LS50W loudspeakers are having an internal Hi-Res DAC but offer the possibility of using an external DAC and voila! A white S6 PRO was already sitting very comfortably near my white speakers (white walkers?!)

Thanks God my KEFs have a remote as sadly S6 PRO doesn’t have one and it is probably the biggest con so far.

I started listening to some Pink Floyd – Hey You and was quite shocked by how much improvement in depth and imaging S6 Pro brought to the table compared to the built-in Hi-Res DAC of LS50W. So far this is the deepest sound coming from my speakers, as pin-point imaging becomes a child’s play really.

Soundstage is just a tad wider than the on-board Hi-Res DAC, this could just the limitation of my speakers that have just a single coaxial driver. Maybe a multi-driver speaker will see even a bigger change, I can only guess.

In terms in frequency response S6 Pro is flat as a ruler with just a tiny treble roll-off for a very natural and life-like performance.

Sub-bas has an impressive slam and kick in the chest, it is also impressively fast and layered. It is a detailed bass that has multiple layers on few electronica tracks. Mid-bass is mostly on the same level and is not overdone. It is flatter than my home DAC in this regard with a linear sub to mid-bass performance.

Midrange is as flat as the rest of the spectrum, but thanks to the Velvet Sound architecture it sounds very natural and just always catches your attention, add that crazy pin-point imaging and singers are like whispering directly into your brain. It is scary real at times, listening at late night I was turning my head very often.

S6 PRO has an impressive meaty tone and timbre, probably among the best timbre I’ve heard in a long time, my home DAC doesn’t have these traits and I’m a bit jealous.

Treble is extraordinarily clean and grain-free, it is very extended with a gently roll-off in the upper treble. It is also extremely transparent and detailed so every cymbal and every bell have a right amount of impact, rise and decline. The more I listen to it the more I am impressed by its fatigue-free and accurate treble.

Since the transparency and airiness are top-level, detail retrieval is at a high level as well and will extract every bit of information from your favorite tunes, it is good on a macro and on a micro scale as well.

S6 Pro is also the fastest AK4497 based DAC I’ve heard so far, it is almost as fast as my ES9038 based DAC, not quite there but it is catching up nicely.

Comparison

I decided to do just a single comparison, otherwise it will outperform a lot of DAC/Amps I covered recently.

This comparison with be a tough one, here it goes.

Matrix X-Sabre PRO (1800 USD) vs Aune S6 PRO (600 USD)

As you can see from the pics, both have about the same size. X-Sabre Pro is using a much thicker aluminum case, it is basically a one piece CNC-ed aluminum block, so it is much heavier. X-Sabre Pro is using a more advanced clock system (best Crystek clocks) and probably the highest performance Noratel R-Core transformer. X-Sabre Pro is based on a single ES9038PRO DAC chip and it is only a DAC or a DAC+Digital preamp, it doesn’t have a headphone amp section.

S6 PRO is obviously AK4497EQ based, and also uses high-peformance analogue parts, just not as high-grade as Matrix does.

Sound-wise this is where it gets interesting, I tested both with my speakers using the RCA outs of both devices.

In terms of detail retrieval X-Sabre wins by just a notch only because it will show more information in the treble area, otherwise S6 PRO is approaching very closely.

In terms of transparency and airiness both are on the same level and I can easily walk thought the recording and dissect any track with ease.

When it comes to depth and imaging, S6 PRO takes the lead, it is just deeper sounding and possess a very precise image around the listener, S6 PRO is very 3D sounding it is almost binaural. X-Sabre Pro is good but not as good at those, that came as a big surprise to me.

Soundstage size is about on the same level and sounds just a hair wider on the S6 PRO, it is really wide spread around the listener, both are champs in this department and are very impressive.

In terms of frequency response both are quite linear and true to the recording, X-Sabre PRO is again just a hair more extended up-top and will playback both frequency extremes (lower-bass and upper treble) better.

In terms of transient response and slam, again X-Sabre wins by just a hair, as the S6 PRO shown impressive kick and slam into my eardrums, I almost couldn’t believe it.

When it comes to naturalness and smoothness S6 PRO is far ahead and will always sound alive and very life-like, X-Sabre Pro presents just a bit of digitus that can’t be avoided in an ESS Sabre design, it is always there to a smaller or a higher degree.

When it comes to headphones, with X-Sabre Pro you will need an extra headphone amp that will add to the cost.

As you can see S6 PRO stood the ground extremely well at 13 of the price versus the X-Sabre Pro and that my friends is really impressive.

Conclusions

This is my first contact with Aune, but I can tell you for sure it will not be my last. S6 PRO impressed me immensely and I am looking forward to their future designs.

Build quality wise it is built to last and looks quite unique, few might be put off by that curved top but it can be resolved with a longer 1.5cm (0.6”) feet for the device that will stay on top.

Sonically as a DAC only device I liked everything about it, I just wish it came with two AK4497 chips for a 100% true balanced output and with a remote control for us, speaker users. I would pay premium for that.

As a DAC/Headphone amp combo it is a head-fier dream as it will have the blackest background even for IEM users and a lot of control and slam with planar-magnetic headphones, with big cans just stay on the balanced 4-pin output and you will be safe. It will not drive heavy-duty headphones as HifiMan HE-6/6SE, Susvara, Audeze LCD-4 and Abyss AB-1266, for that ones a S7 PRO will nicely complement its brother.

So far, this is the best DAC/Headphone amp combo I’ve heard so far, at only 599 USD, it’s the best kept secret of the audiophile world!

S6 PRO can be purchased directly from Aune for 599 USD or for 549 EUR.

PROS:

  • Impressive detail retrieval and transparency level
  • Great speed, impact and slam
  • Very linear frequency response
  • Awesome naturalness, tone and timbre
  • The best depth and pin-point imaging in a DAC of this caliber
  • Open wide soundstage
  • Lack of background noise and distortion even at full volume
  • Great price to performance ratio

CONS:

  • Not a true 100% balanced design
  • Will not drive your shiny 3K headphones
  • Lacks a remote control

ASSOCIATED EQUIPMENT:

  • DACs: Aune S6 PRO, Matrix X-Sabre Pro, Loxjie D20, Burson Swing & Playmate
  • Headphone Amps: HeadAmp Gilmore Lite Mk2, Erzitech Bacillus, Burson Playmate, xDuoo TA-10
  • Speakers: KEF LS50W
  • Headphones: Quad ERA-1, Sennheiser HD660S, Sennheiser Momentum 2, FiiO FA7, FH7
  • Cables: QED Reference XLR, Burson Cable+ PRO, Audioquest & Kimber interconnects, PS Audio power cables

Overall score 92/100

Features & Settings 95/100
Background Noise 96/100
Power Output 85/100
Resolution 90/100
Dynamics 92/100
Frequency Response 94/100
Stage Size 91/100
Build Quality 94/100
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