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Measurement and Review of FX-Audio DAC-X6 DAC (compared to Topping D30 and Fiio E10K)

amirm

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#1
This is a (very) detailed measurements of FX-Audio DAC-X6 audio DAC and headphone amplifier. It also includes my listening impressions as usual. The FX-Audio DAC-X6 retails for just $58 shipped from Amazon: https://www.amazon.com/gp/product/B01HERNVFM/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

upload_2017-11-28_12-27-34.png

Comparisons will be made against Fiio E10K which retails for $78 and Topping D30 DAC ($120). See my review and comparison of those products here: https://audiosciencereview.com/foru...dslabs-odac-rev-b-compared-to-fiio-e10k.2068/. For the second part of this review, I also include the comparison to Exasound E32 DAC ($3,400 retail): https://audiosciencereview.com/foru...xasound-e32-dac-review-and-measurements.1990/

Overview
When I was close to finishing the review, I was under the impression that this was a $120 DAC or more. Imagine my surprise where by accident I landed on its price on ebay and such and see it selling for just $58. There is no way looking at its enclosure and features that you would guess it would sell for so little money. The case is stout, heavy (for this class), and finished well. The volume control has a nice feel with notches thrown in there for good measure (kind of like a rotary encoder except that it is not).

The feature set is quite rich with USB, optical (toslink) and coax S/PDIF inputs. The unit is externally powered which is another unique thing in this low price rage. As such, power consumption from USB port is minimal at 50 milliamps.

Front panel buttons are old fashioned toggle switches but they have a solid, reassuring feel. There is an on/off switch which I like and a button for selecting one of the three inputs.

There are two analog outputs, one line level that is fixed and the other, on the front going through a headphone amplification stage. The knob controls the level of headphone output.

Software
As is common for me these days with the latest "Creators" version of Windows 10, I test these DACs by simply plugging them in and NOT installing any drivers. This unit was no exception and it nicely got recognized by Windows allowing me to use the exclusive mode WASAPI interface to bypass Windows audio stack in Roon. Speaking of Roon, it shows the following formats supported:

upload_2017-11-28_12-36-36.png


So darn good in that front too. Many low cost USB DACs are limited to 96 KHz, not so here.

Reliability was excellent under Roon without any failures using default settings. The only downfall it had was ignoring the volume control level in Roon. So if you rely on that for your volume level for your system, i.e. have no pre-amp, then you can't use this DAC. Hopefully this is a firmware limitation and can be fixed.

As cranky as I can be, I can't really find any faults here with the physical execution and overall functionality with the exception of volume control issue.

Measurements
I am going to present this in two parts. First part in this post is the usual set that you see from me. For the second part, since this DAC has S/PDIF input, I thought I use that on it, Topping D30 and Exasound E32 to run a full suite of measurements. This is made possible by my Audio Precision Analyzer controlling the source signal which is not (easily) possible using the USB port (newer versions of AP support PC control but only using ASIO and not WASAPI). To make sure the data is not overwhelming, I will put these extra measurements in follow on posts.

Let's dig right in with J-Test jitter and noise test:

FX-AUDIO DX-6 DAC J-Test Measurement.png


Nothing like bad news up front. As you see in red, the FX-Audio DAC-X6 has substantially higher noise floor than either Topping D30 (yellow) or its comparably priced Fiio E10K (green). The distortion spikes are at -110 db so not a bother in practice. The noise floor though once adjusted for the way the measurements are done, will land at 90 db or so and hence, is higher than CD playback dynamic range.

Next let's look at harmonic distortion using 1 Khz 44.1 Khz sampling signal:

1 Khz Comparison with Fiio E10k.png


Here we see declining harmonic distortion which is good (compared to Fiio E10k) but there is a rise in noise floor proportional to frequency after 16 Khz or so.

Our current champ of budget DACs, the Topping D30, delivers a big blow to DAC-X6 in this test:

1 Khz Comparison with Topping D30.png


We have lower harmonic distortion in D30 and flat noise floor.

Next let's look at ability to reproduce the lower two bits of 16-bit audio, attempting to approximate a sine wave:

FX-Audio DAC-X6 1 Khz -90 db linearity test.png


I don't know about you but to my eyes, there is no sine wave of any sort in the output of FX-Audio DAC-X6. It is dominated by noise and who knows what else (in red). The cyan one is from Topping D30 which takes the crown again as the best of the three.

So in summary, the Topping D30 continues to outperform other DACs including the FX-Audio DAC-X6. In the three way comparison, Fiio E10K lands in the middle and the DAC-X6 easily finishes last.

Story gets better though when we look at the headphone output:

upload_2017-11-29_0-9-46.png


As we see, courtesy of its external power supply, the FX-Audio DAC-X6 has higher output both unloaded and loaded. Here is what that translates into as far as output impedance:

upload_2017-11-29_0-9-15.png


So not too bad.

I should mention that the Fiio E10 was oscillating at its peak output into my 33 ohm load. I had to turn down the volume to "6" instead of max of "8" for the loaded measurement. The FX-Audio DAC-X6 on the other hand had no such problem so measurement is at its max output.

I also tested the frequency response of the headphone output:

headphone frequency response.png


That response is very poor in high frequencies, dropping from 5 Khz on by as much as 5 to 7 dB. We should see a rule flat output. So better pair this with rather bright headphones to compensate.

Listening Test
I listened to the line output of the DAC-X6 against the Topping D30 through my Stax SRM-007t headphone amp driving their "Pro" headphones. Going through my playlist, I could not detect any obvious differences. But if I squinted enough, I thought the Topping sounded better. See the frequency response measurements for possible reason.

I then switched to headphone listening and comparing the DAC-X6 against Fiio E10K. Without level matching, the DAC-X6 easily pulls ahead. Even with level matching, the DAC-X6 sounded noticeably better with the Sennheiser HD-650. There was more bass, more clarity, etc.

Switching to Hifiman HE-400i headphones, most of the differences went away. After listening for a while, I could still hear some improvement from the DAC-X6 but clearly this is a less demanding headphone than the HD-650 is. It is also more comfortable to wear.

Since the Topping D30 has no headphone output, it is out of the running.

Summary
Measured performance of the FX-Audio DAC-X6 is rather disappointing. It loses to similarly priced Fiio E10K and by a larger margin to Topping D30.

On the other hand, its physical build is far better than the Fiio E10 and even Topping D30. And its headphone output which never gets distorted regardless of its dial position, is able to drive difficult headphones like the Sennheiser HD650.

So if you want a DAC with headphone output for just pocket change, you have found it. The FX-Audio DAC-X6 provides a competent physical package, lots of inputs, and nice headphone amplifier.

As a pure DAC, my recommendation remains to buy the Topping D30. Yes, it costs more but just cut back on morning coffee for a few days and you can afford it! :)

EDIT: Hardware tear down here: https://www.audiosciencereview.com/...are-teardown-of-fx-audio-dac-x6-usb-dac.2115/
 

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amirm

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#2
As promised above, here are a set of new measurements I have not shown before. All are performed with the Audio Precision Analyzer producing the source signal from its coax S/PDIF output and being consumed the same way by the three DACs. These are automated measurements that are much quicker for me to run than the USB ones. So I can run them in the future. Please vote for the ones that you find useful by giving it a "like" and I will consider running them in the future with DACs that have S/PDIF inputs. Longer term I will try to replicate them using USB output but for now, they are limited to S/PDIF.

Let's start simple with the crosstalk test. This is as it sounds: it drives one channel and see how much of it bleeds into the other. This is plotted per frequency because crosstalk as a rule increases as frequencies go up (easier for capacitive coupling of one channel to the other):

Crosstalk vs Frequency FXAudio DAC-X6 vs Topping D30 vs Exasound E32.png


Ignore the Exasound E32 in yellow for a second. The red is FX-Audio DAC-X6 which has highest level of crosstalk in red.

The topping is the best as shown in Green.

The Exasound (in yellow) has some kind of strange problem in that the two channels act differently and crosstalk goes up and down. I have to believe there is some kind of resonance going on at some frequencies to cause those peaks. It is disappointing and should be something that Exasound resolves. Fortunately it is an exception among all of these measurements as you will see.
 

amirm

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#3
Now let's look at THD+N (harmonic distortion plus noise) with respect to digital level.


Exasound E32 THD+N vs Level compared to FX-Audio DAC-X6.png


The Exasound does serious damage to FX-Audio here, showing not only 20 db lower noise floor but also one that is very well behaved with just a smooth increase towards the end of the scale. The FX-Audio has a chewed up response which indicates noise plus other sources of spurious signals.

Looks like I have lost the comparison to D30. From memory, it finished in the middle. Well behaved but not as good as Exasound.
 

amirm

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#4
Here is a simple test of frequency response:

Topping D30 DAC vs FX-Audio DAC-X6 Frequency Response Measurement.png


The carrot goes to Topping D30 of course. It has flat response whereas the FX-Audio DAC-X6 droops at both ends.
 

amirm

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#5
Let's look at linearity test. Here measurement is made between output of the DAC and ideal value it should have. First the Topping D30:

SPDIF Linearity  Topping D30.png


I have put a market at 0.1db deviation from ideal which translates to -92 dbFS. From there on, deviation gets larger. Translating that to "bits," that says that we have about 15 bits of good resolution.

Here is the DAC-X6:

SPDIF Linearity DAC-X6.png


The deviation is around the same point as Topping D30 but then the error becomes wild and incorrect in a hurry, ending at some 8.2 db of error. So clearly a worse implementation than the Topping D30.

Here is what $3,400 buys you in the form of Exasound E32:

SPDIF Linearity Exasound E32.png


At the same 0.1 db of error, we are not up to a whooping -112 db which translates into 18.3 bits of effective resolution. Better yet, nothing crazy happens when we go to to -120 db.
 

amirm

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#6
This is yet another THD+N measurement versus frequency in stereo (pairs of lines for each):

THD+N vs Frequency Topping D30 Exasound E32 FX-Audio DAC-X6.png


What the heck is the FX-Audio doing there??? Your guess is as good as mine.

At the other extreme, the Exasound remains excellent but we see difference in channels. Wonder if the display/microprocessor/digital input is closer to one channel than the other to cause that differing output.

The Topping is well behaved.
 

Sal1950

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#8
I that is it. As you see, money seems to buy more happiness. You can print those graphs and put them on your wall to make you feel good about buying the Exasound E32.
From the Cheapskate's seat, pretty hard to justify the extra $3280 over the D30. The graphs on the wall and leftover cash in my pocket would make me smile more. ;)
 

Thomas savage

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#9
Topping do make a dac/headphone amp as well as stand alone headphone amp and other such variations.. be intresting to test the dac plus amp?
 

mindbomb

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#10
Is there something wrong with the thd+n x level graph? Shouldn't the curve rise with decreasing levels due to increased % noise?

And I didn't realize the e10k had such high output impedance. fiio spec says 1 ohm. is fiio cherry picking frequencies? Though it would make sense for both the e10k and dac x6 to have higher than usual output impedance since they use opamps with very high slew rate.
 
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Blumlein 88

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#11
I know it shouldn't, but if they supply drivers instead of letting Windows recognize it, I wonder if the performance would vary any?
 

amirm

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#12
Is there something wrong with the thd+n x level graph? Shouldn't the curve rise with decreasing levels due to increased % noise?
If you go back to the J-test, you see that we have spikes with full amplitude 12 Khz signal. If I then reduce that signal, anything proportional to it such as jitter and noise will drop to below intrinsic noise level of the DAC. I think that is what we are seeing.
 

amirm

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#13
I know it shouldn't, but if they supply drivers instead of letting Windows recognize it, I wonder if the performance would vary any?
Roon is reporting bit exact output so I don't see how the behavior would change, sans volume control possibly working.

Since I do all of these tests on my main laptop, I hate to keep installing drivers on it. :)
 

mindbomb

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#15
If you go back to the J-test, you see that we have spikes with full amplitude 12 Khz signal. If I then reduce that signal, anything proportional to it such as jitter and noise will drop to below intrinsic noise level of the DAC. I think that is what we are seeing.
Yes, but I would think there would be a more 'check mark' type shape, like this graph from ken rockwell's review of the cambridge audio dacmagic plus.
http://kenrockwell.com/audio/cambridge/dacmagic-plus/measurements/THD-LVL.gif
 

amirm

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Yes to both and welcome to the forum!
Thank you! I look forward to seeing the results.

Glad to be here, I've been meaning to make an account for a while. One question, do you prefer that members of trade be marked here, and if so how do I do that?
 

amirm

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Yes, but I would think there would be a more 'check mark' type shape, like this graph from ken rockwell's review of the cambridge audio dacmagic plus.
http://kenrockwell.com/audio/cambridge/dacmagic-plus/measurements/THD-LVL.gif
I think that is a function of the higher noise level of R&S measurement gear he is using. See his loopback tests showing the same: http://www.kenrockwell.com/audio/rohde-schwarz/upl.htm



Here is data from Audio Precision an another DAC they tested: http://nihtila.com/2017/01/08/understanding-audio-measurements-thdn-vs-amplitude-and-frequency/



And the explanation they give:

"Noise and SNR
On the left side, when signal level is very small, we see the noise floor of the system. In this case it is -113 dBV so SNR is 6 dBV-(-113 dBV) = 119 dB (non-weighted).

THD+N
On the right side of the plot we have THD+N, dominated by distortion. In this case we have clear differences between channels but THD+N ratio would be -107 dB for left channel and -103 dB for right channel (again the ratio of signal level and THD+N level). Or 0.00045 % and 0.00071 %, respectively. I like decibels more."

So completely consistent with the data I have although it is possible to have a DAC that has much higher noise floor.
 

amirm

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#19
Glad to be here, I've been meaning to make an account for a while. One question, do you prefer that members of trade be marked here, and if so how do I do that?
Just create a signature and put association/title/name of the company there as you see in mine.
 

mindbomb

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#20
Ok, I think the reason I had trouble with that graph is that i didn't realize the units were dbv or some absolute type of unit, explaining why the noise would stay about the same even though signal was really low.
 
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