I have the Liquid Spark and the JDS Atom. I also have the SMSL sAp-1 “Class A” headphone amp. It’s like 75$, and you do get a taste of “Class A” smoothness… But a subtle one. I got this Aune X7S for like 150USD shipped and I say, if you can get it for this price, please don’t bother about the sAp-1. Yes, going from any of these (Liquid Spark, JDS Atom, SMSL sAp-1) to the Aune X7S is a heccin huge upgrade.
This review has been done using an SMSL Sanskrit 10th DAC and the X7S’s 1/4" out (I don’t have XLR cables). Headphones used: Sennheiser 6XX, Fostex T50RP, Nad HP50.
Soundstage
Soundstage is a weird thing. It gives you the impression the sound comes from X ft away from you when, obviously, you’re just wearing headphones. What’s even weirder is when you get to “tridimensionality” of sound, but it’s what you get from this amp: Depth plus soundstage. The Aune X7S can add an enormous amount of depth to your audio.
By comparison, the Liquid Spark, the Atom, the sAp-1, all sound like “a headphone amp, for two headphone drivers, making sound for your left and your right ears”… and that’s it. Yes it’s crisp, it’s clear, the boundaries of music are crisp and clear, and the singer is in your face (…or a bit too much “in your head”, sometimes). With the X7S, you’ll press “play” and sometimes wonder if you left your speakers on. If you want headphones to get rid of your stereo system, this is the headphone amp to get.
Ironically, this means I still prefer the Liquid Spark for one thing: It sounds less wide, so the “stage” positioning is more believable (as in, you know, the place where the musicians play, outside). Energetic music sounds way more “in your face” with the Liquid Spark too. Electronic music hits, hard. The Aune X7S soundstage is way larger. Again, “speaker-like”. But for all the following reasons, my “daily driver” Liquid Spark is now in a box.
Soundstage is good, but you don’t buy this amp for the soundstage. You buy it because it’s a Class A amp.
Class A: Harder, better… smoother.
Most headphone amplifiers are “Class D”. Which basically means “This is silence, don’t send me power – okay now I need X watts of power for this drum kick, send it to me”. Most speaker amplifiers and AVRs are trying to do the same using “class AB”. All this to save power. Class A was the “original” way to do amplifiers. And it’s “all the power, all the time if your music needs it”. So… you understand why they don’t make 500W class A “AVRs/heaters” now. But headphone amplifiers don’t need that much power anyways. Some purists will say Class A is the only way to go. Because if there’s anything playing, any little detail to hear somewhere, the powah will always be there for it. In theory, your music will sound fuller, smoother, and more detailed… and that’s what you get with the X7S (…and heat, because unused power is “wasted” as heat).
Gain switches: Available in 2 flavors.
On the bottom of the amp, there’s gain switches allowing you to go from +0dB to +12dB to +20dB gain (oddly enough, for the left and right channels separately). I thought the gain switches would only affect volume, so I didn’t bother. After a few days, I tried the switches and was shocked: The sound completely changed. This is 2 amps in one.
+20dB Gain: The “over-the-top” Class A experience flavor.
Like this, the bass and mids are oh so thick and full, and with the amount of depth it gives you, you’ll have a taste of what some people here with X000$+ DACs and amps call “holographic” sound. But be aware (at +20dB gain) the treble is recessed. THX amps are often labeled as “effortless detail monster amps”, but some people say they’re “soulless” with “sharp treble”. With my Sennheiser 6XX and my Nad HP50’s, the Aune X7S at +20dB gain is the complete opposite: It’s the “effortless detail monster amp” for people who like their music to sound analog, smooth, full, and don’t like treble. You will still hear everything. The treble will just never be as annoying – or exciting – as the other options. Actually, the bass and mids either: Hell, with this switch at +20dB gain my T50RPs don’t even sound like planars anymore: Compressed AF. But… listen to Miles Davis - Blue or Green, grab a glass of whiskey, and enjoy the show.
And the +20dB gain thiccness might make you think the sound is just “muddy”… until you realize you’ve never heard that much detail in songs you thought you knew.
+12dB gain: The “critical listening” flavor… never sounded so life-like.
There, the bass-mids-treble are all there. And the transients and attack and energy is all there. Your planars will still sound like planars. Smooth jazz will also still sound like smooth jazz. Electronic music will also sound as fast, precise and “mechanical” as ever. So… The power is there, the speed is there, the detail is there. Which means, when you find well-recorded music… Welcome to "uncanny valley". It’s not right at all to compare the Liquid Spark and JDS Atom to this one. Maybe not right at all to even compare Class D amps to this one. The life-like sounds coming from this headphone amplifier will make you believe Class A is the only way to go. Sense of depth is diminished compared to +20dB but, lol, diminished to a decent level. Finally, because the treble is back, you’ll notice there’s even more detail… Perfect.
Finally, the 0dB gain is just more of the same +12dB “flavor”, but for IEMs. (it’s probably ~250mW). That’s why I said the Aune X7S is “2.5 amps in one” : One ~250mW version for IEMs (0dB gain), more of the same in ~1 watt version for “Class A analytical-ness: Neutral but smooth, critical listening-worthy and studio worthy” (+12dB gain), and one for “Class A smoothness: After-work relaxation and scotch-worthy” (+20dB gain).
Is the Aune X7S worth the full price of 300$? I’d say no (…but I have the 2018 version, and I don’t know about the upgraded 2021 version – same name, different year). But is the Aune X7S 2018 worth 150$ used? Definitely.