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  1. DarKu
    Aune S7 PRO- Driving headphones to the next level
    Written by DarKu
    Published Jun 25, 2019
    5.0/5,
    Pros - Excellent acoustic transparency and airiness
    Great speed, impact and slam
    Linear frequency response with just a hint of warmness and naturalness
    Weightier and denser tone, moves a lot of air
    Among the widest and deepest sounding solid state amplifiers
    Lack of his, hum or any background noises
    Tons of control and grip over the headphone drivers
    Effortless and easy going
    Lacks distortion even at very high volume
    Paired well with IEMs, portable headphones, desktop dynamic and planar-magnetic designs
    Cons - Has a big volume gap between low and high gain (watch out with IEMs)


    At München High-End Show 2019 Aune Audio unveiled a bunch of interesting products such X1s PRO DAC/Headphone amp combo, X7s stand-alone headphone amp, X8 Magic dedicated DAC, X5s desktop digital music player, but to us the most interesting ones were their flagship series: S6 PRO DAC and S7 PRO balanced headphone amp.

    S6 PRO was covered by us about one month ago, I recommended checking the detailed review right here.

    So, today is the big day for the S7 PRO dedicated headphone amp that will be put through its paces.

    S7 PRO is an updated version of their older S7 design, on the outside both are looking the same, except the PRO badge on the newest device.

    If you are wondering what exactly was updated and improved upon, I reached to the manufacturer for a detailed answer:

    • S7 PRO uses a second-generation AMP-II module (4 modules) which increased power and decreases output impedance for a much better IEM compatibility
    • S7 PRO inherited the Titans Artemis headphone amp circuit but improved upon every aspect of it
    • S7 PRO uses a higher performance ultra-low-noise transformer
    • Few op-amps were swapped with higher performance ones
    • In total 26 components were changed for more stability at low frequencies, for a better ambiance, more naturalness and delicacy.
    Inside the box

    Unboxing experience is excellent, S7 PRO came double boxed for extra protection. The smaller box is made out of very thick card-board. Inside you will find: the S7 PRO, a power cable, a headphone adapter and a user manual. Just attach it to an analog or digital audio source and you are good to go.

    S7 PRO comes in two variants: in a very nice-looking silver or black aluminum case. I think it looks plain in black and more stylish in the silver color, everything just pops. Since we are having a silver S6 PRO, a silver S7 PRO on top of it was just mandatory.

    [​IMG]

    Design & Build Quality

    I was really impressed by the build quality of S6 PRO, S7 PRO looks as stunning but simpler since it is lacking an LCD screen. It is much bigger and heavier than typical headphone amps that we tested of late thus it left a great initial impression on us.

    Front panel is made out of milled thick CNC aluminum plate, it has a grainy sand-blasted like surface that should absorb a lot of use and abuse, typical metal headphones laid on top of it should not pose a problem. I’ll be honest with you, the unusual shape of it started growing on me since the S6 PRO found a place in my home. S7 PRO on top of S6 PRO looks impressive and quite handsome. My wife still didn’t ask what are those 2 big silver boxes so the WAF (wife acceptance factor) is really high with this one.

    I really like that the front, top and side panels do not have a single screw, you will find those on the back or underneath the device. As such, S6 PRO together with S7 PRO are really clean and minimalist looking devices.

    I’m glad to report that the rubber feet on both S6 PRO and S7 PRO are tall enough to be put on top of each other without touching the surface in the middle. I had my doubts first but there is actually some free space for the air to cool them down properly.

    The front panel houses a balanced 4-pin XLR output, a double 3-pin XLR balanced connection and a standard ¼” (6.35 mm) headphone output. There is also a single Select button that carries a double duty: a short press will change the analog input and a long press will switch between 2 gain settings (low and high). The volume pot works in the analog domain and I do like it a lot more than the stepped one in the S6 PRO.

    On the back there are two analog inputs (RCA in and XLR in), a power AC inlet and an On/Off button. As you can see S7 PRO is a very simple and straight to the point device with a sole purpose of driving high and low-sensitive IEMs and headphones.

    The shape seems a bit odd at first sight with an arc-shaped smooth design on top, but it grown on me as I think it looks quite unique and stands out from the crowd.

    [​IMG]

    Tech Specs & Detailed Information

    The S7 PRO headphone amplifier is based on the second generation custom AMP-II headphone amp modules, it has 4 of them for a 100% balanced operation, attach a headphone to the single ended output and you will be using only 2 of those modules. S7 PRO inherited the well-respected Titans Artemis amp circuit that in short terms is a balanced and ultra-low distortion amp circuit framework with an innovative multi-stage parallel driving mode followed by 4 custom Aune AMP-II modules that were further refined in their PRO version.

    I am happy to see high-performance metal-can capacitors, heat sinks for the buffer stages and a big ‘n heavy ultra-low-noise and high current toroidal transformer that should pump a lot of clean power to the AMP-II modules.

    The op-amps in the signal path are used as a buffer for the analog input signal, but the final output stage is op-amp free if that matters to you.

    When it comes to raw power, S7 PRO will offer up to 1050 mW of power into 32 Ω on the SE output and up to 3400mW of power into 32 Ω on the balanced outputs. I know some of you are thinking the S6 PRO with its 405mW on tap should be enough power wise for some dynamic headphones, and to some degree that is true…but S7 PRO is completely in another league when it comes to powering hard to drive headphones with absolute levels of dynamics and control.

    Since it has both a single ended RCA and a XLR balanced input, you can use basically with any analog or digital audio source.

    Having an impressive 4.1 uV of noise and a THD of just 0.0005% the S7 PRO should sound excellent even with very sensitive IEMs and I’m glad Aune put their minds at work acknowledging the importance of low noise and distortion.

    [​IMG]

    Sound Performance

    I. Using S7 PRO with sensitive IEMs

    My listening was done with a S6 PRO + S7 PRO

    Put it simply this way: S7 PRO is noise-free even on high-gain with very sensitive IEMs. FiiO FH7 and FA7, even the affordable KZ AS16 are notorious for picking the noise-floor of any desktop headphone amp.

    With all those three S7 PRO is simply noise free and offers a black and silent background. Noise floor is very low and that is great for all types of earphones or headphones. My former champ in terms of noise-floor was the Gilmore Lite mk2 but S7 PRO trounced that one especially with sensitive IEMs.

    If you are planning on using IEMs and full-sized headphones in a desktop rig, S7 PRO might just be the right prescription for you.

    The second thing that awe-struck me was how effortless and easy going S7 PRO is sounding. I might say this one, so far, is the most effortless sounding headphone amp I had the pleasure of testing at my place.

    Everything just sounds decompressed, expanded around me with a crazy feel of dynamics and control. S7 PRO has some very serious power under the hood and that will be explored in depth with my full-sized headphones.

    When I started listening to Opeth – Eternal Rains Will Come I could swear I had my planars on my head, but nope, FiiO FA7 IEMs were singing so big and wide that I never experienced them this way, even on portable balanced power they sounded tinier and more closed-in.

    That complex mix of musical instruments didn’t clutter and overcrowd the performance in any way. It’s important reminding myself that S7 PRO is doing that without rolling off the frequency extremes.

    [​IMG]

    Continuing my playlist with Opeth – Windowpane I started tapping my feet wildly as the musical performance is quite uplifting and leans towards a musical side than to a boring linear experience. Of course, a lot of this magic comes from the S6 PRO as well, with its natural performance and velvety smooth decay of the notes. If headphones amplifiers could be compared to Digital-to-Analog converters then S7 PRO would definitely be a R2R NOS design.

    Another thing that catches my attention is the soundstage size and depth. If I would guess from the start with the eyes closed what I am listening to, I would swear I am listening to a hybrid design with a vacuum-tube hidden somewhere inside, as S7 PRO leans towards an expansive and wide soundscape, it will never sound up-front or over-crowded.

    S7 PRO doesn’t posses a stridency up top, it is mostly linear with a mild warm tone, it sounds calm on blues and dynamic on hard kicking tracks. Older recording such as The Beatles and Led Zeppelin will sound meatier with a higher dose of naturalness. The hiss and grain of the recording is there but doesn’t scratch my ears. I observed that drums and guitars in particular are more natural sounding compared to my other headphone amps. Overall, the music carries more weight with it and decays in a natural way.

    [​IMG]

    II. Using S7 PRO with desktop full-sized headphones

    The openness I was writing about on IEMs it is even more pronounced especially with open-back headphones. The airiness S7 Pro is having is very apparent with instrumental music so every note will just float in its own air bubble with a clear leading edge and outline.

    Pin point imaging is great, but not super defined and clear since the notes are almost far away from the listener and I would detect the distance between me and a said note a little bit harder. All the headphone amps that have a smaller stage with have a clearer but tinier image.

    Listening to No Doubt – Hella Good the drums and bass notes are like hitting my whole body and not just my timpani, a very weird feeling. It’s quite interesting that when this tune becomes crowded, it doesn’t bottleneck the musical performance and manages putting those notes around me so naturally and believable, every note is floating again in its own space.

    Listening to Hans Zimmer – Interstellar OST there are a lot of moments of complete silence which immediately jumps to a high volume. The air pressure jumps instantly and kicks hardly, dynamics are on a high level with this one. I can hardly distinguish the borders of the soundstage on few tracks as the notes are flying to no end.

    Since the noise floor is really low and the SNR numbers are very high, S7 PRO will not block the micro-detail information sent by the audio source, so it will always sound clean, detailed and very precise.

    [​IMG]

    I consider that micro-detail information is not lost on it, add a crazy transparency and airiness and you could already presume that I just pick-up sounds from the air quite easily.

    Transient response is fast but not the fastest I’ve heard in the business. S7 PRO is almost never aggressive sounding, that is a trait for me since I can listen even to bad mastered music or overcrowded performances.

    Listening to faster tunes (basically 80% of my music) resulted in good kick and impact but again in a natural, smooth fashion without listening-fatigue whatsoever.

    Listening to folk and folk-rock was a real delight, it is slow and dynamic in the same time on some passages. S7 PRO can sound raw and hard kicking but also gentle and slow with the right music.

    It is worth mentioning that with the S6 PRO DAC+Headphone amp combo I was almost maxed volume wise with my planar-magnetics but on S7 PRO I never would pass the 12:00 o’clock position. If needed, S7 PRO can be very loud!

    There is one thing that bothered me a bit: the gain. The difference in loudness between low and high gain is really big, if you are listening to a pair of IEMs on the low gain, be careful changing the gain to high, lower the volume first before doing that. With full-sized headphones that issue is not as big but still bothers me a bit. On low gain I can easily max the volume and on high gain I can’t go higher than 50% volume wise. With a hoter audio source like the 4.5 Volt X-Sabre PRO or the uber-hot 9.7 Volt Mytek Brooklyn DAC+ I would not pass the 30% volume position, Crazy!

    If power is what you are craving for, S7 PRO has that in spades and some more.

    With great power comes great responsibility and this is where S7 PRO again shines: Control. S7 Pro has a mighty grip over the headphone drivers. There wasn’t a case when S7 PRO would sound loose or muddy.When it comes to headphone pairings and overall performance, I can’t seem to find obvious flaws.

    Since the S6 PRO has a very mild midrange boost and wider soundstage, the S7 PRO immediately shown that as well. Attaching it to the Mytek Brooklyn DAC+ revealed more treble information and a flatter performance. Changing the DAC with a Matrix X-Sabre Pro added a bit of bass thump and overall speed. So, all in all S7 PRO will mostly show the DAC sound signature without adding much in terms of frequency response.

    [​IMG]

    Comparisons

    I know that all Aune S6 and S6 PRO owners are probably wondering if adding the S7 PRO to their acoustic chain will make their headphone experience better, so here we go.

    Aune S7 PRO (599 USD) VS Aune S6 PRO (599 USD)

    I tested mostly on the balanced 4-pin XLR headphone amp to have a better idea.

    The general idea is that S6 PRO is quite fine with dynamic headphones and with all IEMs, dynamics and transients are there, layering and pin-point imaging is there as well. The biggest downgrade on the S6 PRO alone is the effortlessness, control, headphone drive and soundstage size.

    Adding S7 PRO to the chain the music starts playing in a bigger room, sounds are flying further away, headphone drivers will have a better grip and as a result everything just sound effortless, uncluttered and easy going. Even my 150 Ohm Sennheiser HD660S sounded livelier and faster on the S7 PRO.

    With IEMs the difference is close to zero but with hard to drive headphones is completely another story.

    Let’s not forget that the headphone output of S6 PRO was mostly put there for convenience. Do you own the S6 or the S6 PRO and consider yourself a headphone aficionado? Do yourself a favor and add the S7 PRO to the chain, your headphones and ears will thank you later.

    [​IMG]

    Aune S7 PRO (599 USD) VS Headamp Gilmore Lite Mk2 (499 USD)

    Gilmore Like Mk2 is my former reference single ended headphone amp. I like it a lot because it stays away from the musical performance and doesn’t add anything from itself. It however possesses some flaws: one is the power output; it is rated at maximum 1W with low-impedance headphones. By comparison S7 PRO offers 3.4W at the same impedance rating, it is just much more powerful.

    If demanding headphones are driven, then headroom is close to zero with Gilmore Lite, I am often at max volume with planar-magnetic headphones. S7 PRO by comparison has tons of headroom left, so much better dynamics at higher volume and on higher dynamic range tracks.

    Another issue is that Gilmore Lite Mk2 has a small-ish, almost 2D soundstage, with the wrong headphone it is quite pale and up-front sounding. Some like that, some don’t.

    S7 PRO is completely different offering a much wider and deeper sound, it is very 3D by comparison.

    Since Gilmore Lite Mk2 has an external but lower performance switching power supply, more residual noise enters inside the amp and it just has more hiss and hum with sensitive IEMs. By comparison S7 PRO blocks a lot more residual noise from the wall-wart and has among the lowest noise-floor.

    To me S7 PRO is a better device and Gilmore Lite Mk2 will soon search for a new home.

    [​IMG]

    Conclusion

    You probably guessed that S7 PRO impressed me dearly with every musical genre I thrown at it. It was impressive with sensitive IEMs and harder to drive headphones alike. There isn’t a headphone in my stable that would need more than 50% from it, having so much headroom left makes it ideal for headphone enthusiasts like myself.

    Since it has just a hint of warmness, an effortless natural presentation it paired extremely well not only with Aune’s own S6 PRO but with any digital sources I tested it with.

    It offers single ended inputs and outputs and can be a 100% balanced headphone amp, it is quite versatile and easy to use.

    So far, this is among the best headphone amplifier I put my hands-on and it is very recommended.

    S7 PRO can be purchased directly from Aune for 599 EUR (for EU residents) and for 599 USD (for USA and rest of the world)

    PROS:

    • Excellent acoustic transparency and airiness
    • Great speed, impact and slam
    • Linear frequency response with just a hint of warmness and naturalness
    • Weightier and denser tone, moves a lot of air
    • Among the widest and deepest sounding solid state amplifiers
    • Lack of his, hum or any background noises
    • Tons of control and grip over the headphone drivers
    • Effortless and easy going
    • Lacks distortion even at very high volume
    • Paired well with IEMs, portable headphones, desktop dynamic and planar-magnetic designs
    CONS:

    • Has a big volume gap between low and high gain (watch out with IEMs)
    ASSOCIATED EQUIPMENT:

    • DACs: Aune S6 PRO, Matrix Audio X-Sabre Pro, Mytek Brooklyn DAC+, Burson Swing & Playmate
    • Headphone amps: Aune S7 PRO, Headamp Gilmore Lite mk2, Erzetich Bacillus, Burson Playmate, xDuoo TA-10
    • IEMs: FiiO FH7, FA7, KZ AS16
    • Headphones: Audeze LCD-4Z, Sennheiser HD660S, Quad ERA-1
    • Cables: QED Reference XLR, Burson Cable+ PRO
      someyoungguy, Xinlisupreme and volly like this.
    1. View previous replies...
    2. DarKu
      I'm pretty sure CMA400i is a fine sounding DAC and amp, enjoy your music!
      DarKu, Jul 30, 2019
      Xinlisupreme likes this.
    3. Reactcore
      Thanks D, i sure will
      Reactcore, Jul 30, 2019
    4. Xinlisupreme
      Amazing review!
      I’d pair it with Chord Hugo and Focal clear, but I’m curious also about Drop THX789...
      Xinlisupreme, Aug 21, 2019