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Review and Measurements of Aune X1S DAC & Amp

amirm

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#1
This is a review and detailed measurements of Aune X1S DAC and headphone amplifier. It is a kind loan from a member who has waiting for its review since last fall! The X1S seems to be have been out for a while, having found a review of it going back to 2015. It is still available though and costs USD $259 from Amazon including prime shipping. This is nice since US customers at least don't have to wait for it to arrive from China and early customer support issues can be resolved by just returning it to Amazon.

Aune has its own "design language" which I like. It shouts "high-end" even though the price is in budget category:

Aune X1S DAC and Headphone Amplifier Review.psd.jpg

The unit has the matt/fine textured finish that is popular these days and picks up smudges easily. I had to touch up the above in photoshop fair bit even though I cleaned the unit prior to taking the picture with a microfiber.

As you see, the input is rather plain with an analog volume control and an input button. If you hold that button down for a bit you enter the setup and you get to decode morse code to figure out how to change settings. Fortunately there are not that many things you can change so you can get through it.

Somewhat unusual in this price range is the ability to just use the headphone amplifier by itself using rear RCA inputs.

We also have our usual three digital inputs of USB, Toslink optical and S/PDIF coax. But in another nice twist, there is also coax output so you can use this as a USB to S/PDIF bridge if you don't like the rest of the unit.

Power is provided through an external, large transformer/linear that provides both positive and negative voltages (12 volts) through a multi-pin DIN connector. This makes the internal design simpler (and potentially better) because the negative supply does not need to be generated by a switching power supply. I don't recommend trying to replace it anyway but if you want to pair another power supply with it, your choices will be highly limited.

The power supply cabling is a bit of pain though. It has two 3 to 4 feet cables to AC and the DAC. The DAC side is too short to connect to the DAC if you leave it on the floor. And if you put it on the desk, you need to have an extension cord as it may not reach your AC outlet either. Given how ugly and big it is, it would have been nice to have a longer DC cord so that you could hide it on the floor.

The X1S is UAC2 compliant and I needed no drivers to get it working on Windows 10 Creators edition.

As I noted the volume control is analog so no remote control is provided.

The internal DAC chip uses is ESS 9018K2M.

Let's see how it does on the bench.

DAC Measurements
As usual with these combo units I start by testing the DAC portion alone. So I connected the RCA out which have a fixed output to my Audio Precision analyzer:
Aune X1S DAC and Headphone Amplifier Measurements.png


As we see the unit runs a bit "hot" with 2.2 volts instead of 2 volts (shouldn't be an issue though).

Distortion is quite low with the third harmonic being dominant at -112 dB or so which naturally sets the THD+N/SINAD value to 111 dB. This is a bit better than the specified 110 dB. Not surprising since the manual comes with a set of measurements performed with Audio Precision! This strong SINAD value puts the unit in the top tier of all DACs tested:
Aune X1S DAC and Headphone Amplifier SINAD Measurements.png


All DACs that do better than it are considerably more expensive. Yes, the slightly higher output voltage may be giving the X1S some advantage here so don't go nuts on this point. :)

Dynamic range is excellent too:

Aune X1S DAC and Headphone Amplifier dynamic Range Measurements.png


Would jitter test let us down or will the good news continue?
Aune X1S DAC and Headphone Amplifier Jitter Measurements.png


The noise floor is very low so it reveals tiny spikes but they are way, way below threshold of hearing at -135 dB and lower. There are some power supply related spikes visible on the left but again, levels are at -130 dB and lower. And I could have probably reduced them by messing with grounding but I did not bother.

How about linearity? Surely this budget DAC will do something wrong there, no?
Aune X1S DAC and Headphone Amplifier Linearity Measurements.png


Nope. It nails that too. How about multitone?
Aune X1S DAC and Headphone Amplifier Multitone Measurements.png


Nothing out of ordinary here either.

Come on, we need something to complain about! :) And this it:
Aune X1S DAC and Headphone Amplifier IMD Measurements.png


We have our classic "ESS Hump" where distortion rises at mid levels. The noise level is very low so it looks even more pronounced than previously tested ESS based DACs. The X1S makes up for it though by keeping its distortion below noise level until we get to absolute max level. In contrast, the Topping DX3 Pro which is its direct competitor starts to distort some (hence the reason its SINAD is not as good). Being based on AKM dac chip though, the Topping DX3 Pro has no mid-level distortion.

I tested the filter response using the first setting (sharp?) and got this:
Aune X1S DAC and Headphone Amplifier Filter Response Measurements.png


I like to see a sharper filter that truncates out of band frequencies (above 22.05 kHz for 44.1 kHz sampling) a lot more than this. This seems to be a typical choice these days.

Headphone Amp Measurements
The King of measurements here is distortion+noise relative to output power. So let's start there with 300 ohm load:
Aune X1S DAC and Headphone Amplifier Power at 300 Ohm Measurements.png


I like to see more than 100 milliwatts of power and the Aune X1S gets there easily with 140 milliwatts with no distortion! It bests the DX3 Pro in high gain in that regard but loses in overall noise level to DX3 Pro especially in low gain mode.

Let's switch to 33 ohm load and see how much current the unit has to drive such low impedance loads:
Aune X1S DAC and Headphone Amplifier Power at 33 Ohm Measurements.png


Here, the X1s falls behind DX3 Pro, starting to clip earlier at 270 milliwatts.

Channel balance unfortunately is off at low volume levels:
Aune X1S DAC and Headphone Amplifier channel imbalance Measurements.png


Given lack of low gain setting, this may be more of a problem with sensitive IEMs than it would be otherwise. The Topping DX3 Pro has digital volume control so has perfect channel matching.

Last bit of not so good news in this department is output impedance:
Aune X1S DAC and Headphone Amplifier Output Impedance Measurements.png


5.9 Ohm is not end of the world and should be good for many headphones but ideally we would want to see 2 ohms or less.

Listening Tests
As usual I started my listening tests using my Sennheiser HD-650 headphones. Here, there was plenty of power to drive it to thundering level. Not much margin was left though and I could detect some distortion at max volume.

Same situation existed with Hifiman HE-400i which sounded excellent through the Aune X1S. It however got distorted earlier and sounded more harsh during the last 20% of the volume range.

Really though, the performance was still excellent with both of these headphones which tells me you will have similar experience with a wide range of headphones.

Conclusions
Despite its age, the Aune X1S provides a very strong showing. You can tell it is well engineered with proper design verification as indicated by my measurements but also inclusion of measurements graphs right in the manual (much like Topping). What holds it back a bit are design choices such as ESS DAC chip, no digital volume control, and less than ideal output impedance.

The direct competitor to Aune X1S is the Topping DX3 Pro which has far more features (LED display, variable RCA out, Bluetooth). Alas, as of this writing the DX3 Pro there are reports of reliability issues causing many to turn away. For those people, and really in general for other preferences, the Aune X1S provides an excellent alternative.

Needless to say, I am happy to recommend Aune X1S as a well engineered DAC and headphone amplifier. It is proof yet again that going by such things as chip specs is a fool's path. What you want is excellence in execution Aune brings that in spades here.

------------
As always, questions, comments, recommendations, etc. are welcome.

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NTomokawa

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#2
Another relatively well-engineered yet affordable that puts countless "high-end" devices to shame.

I wonder why it uses a DIN power jack, though. The included PSU doesn't seem to be UL-certified either...
 
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#3
Did you at least do a quick check on the other digital inputs? Seems like execution on those is not always commiserate with whatever is going on with the USB input.

Similarly, I'd be interested in how it does with the line-in's. That's kind of a unique feature among these DAC-amp combos.
 

amirm

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#8
I felt sorry for owner every time I noticed it was still in the queue. Perhaps we can give him a special knighthood for service to the cause.
Problem was that I had put it in the pile of my own gear and hence, lower priority to review. I need a better filing system which is hard when you don't have any filing system! :D
 

Willem

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#9
I had been very interested in this unit until I discovered that unlike its predecessors it does not have a variable line output. So it will not work as a pre amp.
 

Willem

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#11
And my perennial complaint: only one optical and one coaxial input. That is not enough for a CCA, a tv and a disc player.
 

Veri

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#12
It's the K2M version. Scaled down for use in mobile devices (?). So far the hump has only been present in the non-full size chips?
In full size too but much harder to spot. Better parts variation or something.
 

Yuno

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#13
Very nice to see good results on my old DAC. Compared to dx3 pro, to me there is audibly no difference. The only difference really is in functionality. Aune feels like much more premium product on the other hand, and I never had any issues with it.

I wonder why it uses a DIN power jack, though
I could never figure out this choice too. Getting extender cable that fit was major pain. I disassembled power supply at one point and found out there are 2 wires going into 5 pin connector. What is the point of this?
 

confucius_zero

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#16
so... this or the EL DAC?
 

graz_lag

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#18
... I could never figure out this choice too. Getting extender cable that fit was major pain. I disassembled power supply at one point and found out there are 2 wires going into 5 pin connector. What is the point of this?
Apple's way ... You are forced to buy the extension cord from them ... Aune in this case ...
 
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#19
This was my first dac/amp combo unit and it's been great! As many have stated and your measurements stand behind this the dac portion is great and the headphone portion is the weaker link. The great thing is combining this dac with any one of the $100 amps yields great sounding results.
 

NTomokawa

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#20
I disassembled power supply at one point and found out there are 2 wires going into 5 pin connector. What is the point of this?
Well that should be a simple mod. Get a tip-ring power jack (one of these things) and replace the DIN jack with it.

Then buy a matching UL-certified wall wart. Of course, confirm polarity beforehand.

I hate proprietary connectors.
 
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