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Ciúnas DAC USB DAC Review

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amirm

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#1
This is a review and detailed measurements of the Ciúnas USB DAC. It is on kind loan from a member who sent it to me following my teardown of a non-functioning Ciúnas ISO-DAC. The DAC costs Eruo $400 (I think). I believe the company has moved away from this specific unit which uses a battery to one that uses super-capacitors. I will do a teardown on this unit later to find out which is which.

EDIT: the original version of this review referred to this product as "ISO-DAC." The company owner provided feedback that it is just called Ciúnas DAC. I have corrected the text of the review to reflect that. Modifying the graphs takes a lot more time.

The enclosure for DAC is as ordinary as it gets:

Ciúnas ISO-DAC Audio Review.jpg

There are no indications of sample rate, etc. on the unit. For this kind of money, I would have hoped for something more substantial than a hobby box.

The back button shows lack of any input other than USB:

Ciúnas ISO-DAC back panel Audio Review.jpg

An external 7.5 volt, 1 amp little switching adapter is provided. It doesn't have a brand name on it but searching for part number, it shows that it is from a Chinese company with a safety certification. So the fact that the grommet that is on it is lose, can be forgiven. Maybe....

I could not get the DAC to work reliably with ASIO4ALL wrapper but fortunately, a driver is provided and that worked fine.

As far as design,it is claimed that the unit runs on internal battery and that is supposed to improve the performance. We will see about this.

DAC Audio Measurements
Nothing like having such a low expectation that anything above failing grade impresses:

Ciúnas ISO-DAC Audio Measurements.png


It was a relief really that the SINAD (THD+N inverted) wasn't at the bottom of all DAC tested:
Best USB DAC 2019 Reviewed.png


Notice the spike at 120 Hz and its harmonic at 240 Hz. These spikes are generated when AC mains at 60 Hz is rectified (converted to double positive AC waveform). This would be in the external switcher and it is happily travelling through the DAC and coming out the other end. This, despite what is said about the design:

1573257212979.png


There are many sources of such ground currents from the charger, to USB and because balanced XLR outputs are not used, through interconnection to downstream audio devices. And I can tell you that there are no capacitors right at the DC input to the device.

The unit is rather quiet:
Ciúnas ISO-DAC Dynamic Range Audio Measurements.png


Frequency response is flat so let's not have discussion of it sounding "warm:"
Ciúnas ISO-DAC Frequency Response Audio Measurements.png


Filter response is not that great:
Ciúnas ISO-DAC Filter Response Audio Measurements.png


A lot of DACs ship with rather slow filter response which truncates around 24 kHz. So that is not a problem here. What I would like to see there though is much better attenuation than 53 dB.

As is typical, there is talk of clean clock with nary a measurement proving the same:

1573257656973.png


So let's measure it ourselves:
Ciúnas ISO-DAC Jitter Audio Measurements.png


Wow, what is this? Those side shoulders should be all the way down at or below the "audiosciencereview" logo for the device to be low noise. Instead, they are so high that make the typical random noise jitter around the main 12 kHz tone, look low.

Besides random noise/jitter, we also have clear pulses which could be jitter, or just plain interference rising up to -96 dB or so. Good desktop DACs achieve levels that are below -115 dB or better.

People who don't really understand mixed-signal electronic design with the level of fidelity we require in audio, make a mistake of not realizing that the output of the DAC gets polluted by many factors, not just how clean the output of some oscillator is. So to get the DAC to have very low noise and "jitter" you need to have an end-to-end clean design. Clearly that is lacking here.

Here is an example of that in recently reviewed SMSL M500 DAC and Headphone Amplifier:



You really have to suspend reality to think that the DAC is "low jitter and noise" design.

The noise gets worse when we look at intermodulation distortion versus input level:
Ciúnas ISO-DAC IMD Audio Measurements.png


It starts "OK" but then suddenly one channel and then the other start to produce lots of intermodulation distortion. With a -20 dBFS signal, the distortion is at -72 dB, only 52 dB separating them. This is probably low enough to not be audible to most people but come on, why generate distortion all of a sudden? One run of this test would have pointed out this problem which can be measured even on a sound card and a PC.

Surprisingly I did not see the same problem with 32 tone test:
Ciúnas ISO-DAC Multitone Audio Measurements.png


The next test, THD+N versus frequency response presented a horrific picture:
Ciúnas ISO-DAC THD+N vs Freq Audio Measurements.png


This test can misfire though in including ultrasonic noise that is not normally audible. So I fed the DAC a 1 and 10 kHz (separate runs) and see the spectrum:

Ciúnas ISO-DAC 1 kHz and 10 kHz FFT Spectrum Audio Measurements.png


The harmonic distortions of the 10 kHz tone (20, 30, etc.) are definitely taller than that of 1 kHz so non-linearity is increasing with frequency. The slow roll off the reconstruction filter is also contributing to some extra spikes.

Finally here is our linearity test:
Ciúnas ISO-DAC Linearity Audio Measurements.png


We lose level accuracy below -90 dB or so. As such, anything at CD resolution or better will not be reproduced with accuracy.

Listening Tests
To see if I can hear these measured problems I connected the Topping DX3 Pro DAC and Ciúnas DAC to dual inputs of my Stax SRM-007t headphone amplifier. The SRM-007t has a nice toggle switch in the front which allows rapid switching between the two inputs. Matching levels was hard because the DAC has higher output. I enabled DSP volume in Roon and knocked it down by 1 dB (did the same for DX3 Pro but set it to 0 dB). This got me within 0.5 dB which is not ideal but was better than not doing it.

I put the two DACs in the same zone and hit play. While I could detect tiny differences, nothing was reliable either immediately or across a full hour of listening. To wit, none of this is true as claimed by the manufacturer:

1573258769289.png


What I heard was the function of what I played. No more, no less.

Again, this is in a controlled, level matched setup. Test the unit by itself and you can easily read any and all such things into the sound you hear. Not just because you are biased by above writing but because you focus more, so you hear more detail.

The measurements back the fact that there is no ability in DAC to bring out more detail. Its linearity test for example clearly show error in what it produces as we get down to 16 bits or better. Jitter shows that performance is worse than vast majority of DACs we test.

Conclusions
The heart of the Ciúnas DAC from measured performance point of view seems like some cheap $30 DAC part you can buy from China. Not totally broken, but not remotely competitive with properly designed $99 DACs. Heck the venerable $9 Apple USB-C dongle matches or beats its performance.

And it is not like you get pride of ownership in having this unit. It comes in a non-descriptive and cheap box and power supply which gives you no joy. After the initial false conclusion wears off that "it sounds better" you are left with an ugly black box and hundreds of dollars out of your pocketbook.

To be bluntly clear, there is not one area of performance here that shows excellent engineering. All the paper talk on their website is just that: talk. Not one measurement are provided for things like noise and jitter which we can readily measure. As far as I can tell, it is an exercise to lego-build mythical ideas in audiophile world by non-technical people of this and that mattering. In reality the DAC actually performs worse, not better.

Please stay away from such products. I don't know how to say it more simply. Save money by buying transparent DACs that don't add a heap of distortion on top of your music. And use the rest of the savings for good food, music or other useful things in life with your loved ones.

EDIT: see the tear down here: https://www.audiosciencereview.com/forum/index.php?threads/ciúnas-iso-dac-usb-dac-teardown-2.9809/

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

I was tempted to use the headless panther for this review but opted for "I don't know" panther instead. Well, the headless panther just put me on notice that I must be discriminating against him so I should expect a letter from his attorney soon. I am going to need money to defend myself. So I appreciate you all donating what you can using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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KMN

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#8
If the testing ^^^ was run without the power supply plugged in, ie off the batteries, where is the 120Hz coming from? A low cost switcher would presumably be presenting ripple at a much higher frequency than that. Not too bad of results. I can't wait for the under the hood photos.
 

MediumRare

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#9
I put the two DACs in the same zone and hit play. While I could detect tiny differences, nothing was reliable either immediately or across a full hour of listening.
Is it a fair conclusion that, even though other products test better, measures of SINAD -85, SNR -107, IMD -72, Jitter -96 are all essentially "transparent"?
 

Tater Tot

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#10
Why is the "shoulder" from the 12khz tone under the noise floor? I have never seen that before.
 

Blumlein 88

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#13
Actually this might confirm or not if the previously tear-down was for an original or modded product.
I'd lay pretty heavy odds the previous teardown and this one will show the same construction quality.

BTW, I said this unit was Schrodinger's cat of DACs, because it only failed and had shoddy construction when the box was opened. Today I see where some new science can tell if the cat is alive or dead without opening the box. Oh well, irrelevant really, I believe this box when opened will confirm the first box was a normal production unit.
 

Kane1972

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#14
Quick question. When doing the listening comparison tests @amirm, what source are you using and how do you connect to both DAC's simultaneously?
 
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#16
Quick question. When doing the listening comparison tests @amirm, what source are you using and how do you connect to both DAC's simultaneously?
I would guess as he is using roon, 2 separate USB cables out of computer, one to each DAC and (as he says) Roon allows you to group multiple outputs to play the same track.
 

Eirikur

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#17
I find this a very interesting result and cannot wait for the tear-down, let's see if this is a fire hazard too.

If anything, these measurements may be proof that audio (production) technology is already to the state you can flop some of-the-shelf made in China components together, do a poor soldering job, throw caution to the wind when it comes to component placement, do a soldering job that makes a grown man cry, and still get an acceptable audio result!

[Edit] Did I mention the soldering?
 
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Killingbeans

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#18
If anything, these measurements may be proof that audio (production) technology is already to the state you can flop some of-the-shelf made in China components together, do a poor soldering job, throw caution to the wind when it comes to component placement, do a soldering job that makes a grown man cry, and still get an acceptable audio result!
I was going to write something, but that pretty much sums it up :D

If this doesn't point to built quality and features as being 99% of what you should pay for in a DAC, I don't know what does.
 

audio_tony

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#20
These spikes are generated when AC mains at 60 Hz is rectified (converted to double positive AC waveform). This would be in the external switcher and it is happily travelling through the DAC and coming out the other end.
If it has an internal battery for power, surely it doesn't need the mains adaptor in use?

@amirm Could you try testing it just on battery power alone?
 
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