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Singxer SDA-2 DAC and Headphone Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Singxer SDA-2 DAC and balanced headphone amplifier. It was kindly sent to me by shenzhenaudio online store. The SDA-2 costs US $580 from them.

The SDA-2 is a rather serious looking DAC with a professional feel:

Singxer-SDA-2-DAC-DAC-and-Headphone-Amplifier-Review.jpg
I like the yellow dot matrix display showing me everything at a glance. And the buttons to directly select what you want rather than going into menus. I do wish that if you are trying to change the volume for it to show that in large fonts so that you can see it from across the room. For desktop use it is not an issue.

I did not take a picture of the remote but it is a step above in what comes from competitors with an ergonomic back and properly labeled buttons.

The back panel sports nice connectors and usual set of inputs and outputs:

Singxer-SDA-2-DAC-DAC-and-Headphone-Amplifier-Back-Panel-Connectors-Review.jpg

No Bluetooth though which increasingly becoming standard in desktop DACs.

The SDA-2 is plug and play with Windows as are just about every DAC these days. It barely gets warm on one side. So really, nothing to complain about and a lot to like.

DAC Audio Measurements
Let's start with our dashboard using XLR output which is used in all of the tests that follow:

Singxer SDA-2 DAC DAC and Headphone Amplifier Measurements.png


Nice to see right on the money frequency and 4 volt output. Distortion products are near -120 dB so utterly inaudible although not class leading:

Audio DAC 2019.png


Dynamic range is excellent, easily exceeding anything content you may throw at it:

Singxer SDA-2 DAC DAC and Headphone Amplifier Dynamic Range Measurements.png


Use of an AKM DAC chip and lower noise implementation easily bests Topping DX3 Pro using the same (but at less than half the price);

Singxer SDA-2 DAC DAC and Headphone Amplifier IMD Measurements.png


The rising distortion above -15 dB seems to be typical of AKM DACs. They have low noise and no mid-level intermodulation distortion like ESS DACs may have but lose at the max level. You choose your trade off.

Jitter and spurious tone performance was excellent:
Singxer SDA-2 DAC DAC and Headphone Amplifier jitter Measurements.png


Linearity showed superb accuracy down to -120 dB/20 bits that I normally measure:
Singxer SDA-2 DAC DAC and Headphone Amplifier Linearity Measurements.png


For grins, I lowed the threshold to -130 dB to see if it aces that too and it indeed did:

SDA-2 Linearity -130 dB.png


Someone paid attention to make sure what comes out of the DAC has precisely the level it needs to have.

Note that this test filters everything but the original tone being fed to the DAC. In use you would not have such a filter so the output would be swamped by noise so don't think you will be able to actually play -130 dB/22 bit content. You cannot.

So far the results have been great but I noticed a sign of some issue when running our 32-tone to resemble music:
Singxer SDA-2 DAC DAC and Headphone Amplifier Multitone Measurements.png


We see more intermodulation distortion at low frequencies. Same showed up in wideband test of frequency versus THD+N:
Singxer SDA-2 DAC DAC and Headphone Amplifier THD+N vs Frequency Measurements.png


Strangely the Singxer supplied measurement doesn't show this behavior. To dig in, I ran an FFT of a 50 Hz tone and got this:

Singxer SDA-2 DAC DAC and Headphone Amplifier 50 Hz FFT Measurements.png


We see clear harmonics at 100, 150, 200 Hz and beyond. Fortunately our hearing threshold for low frequencies is very high so none of this is audible.

Here is the response of various filters and what they call it on the display:
Singxer SDA-2 DAC DAC and Headphone Amplifier Filter Measurements.png


Wish there was an ultra-sharp filter that truncated at 22.05 kHz or thereabouts.

Headphone Output Measurements
The SDA-2 has a discrete headphone amplifier which seemingly has a lot more headroom than what the DAC portion can drive. This is seen in our power versus input level in that we don't see any clipping:

Singxer SDA-2 DAC DAC and Headphone Amplifier Power into 300 ohm Measurements.png


We do have elevated noise level but good amount of power, clearly my threshold of 0.1 watt or 100 milliwatts.

Same with 33 ohm load:

Singxer SDA-2 DAC DAC and Headphone Amplifier Power into 33 ohm Measurements.png


Testing with 50 ohm load both from 1/4 inch and XLR we see the higher power output of the latter:

Singxer SDA-2 DAC DAC and Headphone Amplifier Power into 50 ohm Measurements.png


With 2.6 watts on tap from front XLR connection, you should not have issues driving just about any headphone to ear bleeding levels.

The higher noise level translates to less than optimal signal to noise ratio to drive ultra sensitive IEMs:

Singxer SDA-2 DAC DAC and Headphone Amplifier SNR Range Measurements.png


headphone amplifier noise performance measurement.png


It is a shame that the baseline noise level is higher in the headphone amp than the DAC.

Having looked at the specs from Singxer indicating 10 ohm output impedance, I was worried going into this test as that would be too high in this day and age. To my pleasant surprise, the output impedance was far lower at just 2.5 ohm:

Headphone Amplifier Output Impedance Measurement Table.png


I measured this a few times and it was indeed this low. Their webpage says it is less than 10 Ohm but this is far less. Anyway, it is good news so we take it. :)

Headphone Listening Tests
The high power and very low distortion of the SDA-2 predicts great listening performance and that is what it delivers. It had plenty of power, able to drive both my Sennheiser HD-650 and Ether CX headphone to exceptionally high levels. The sound was dynamic, detailed and reflected the fidelity of my recordings. Subjectively there was no fault I could find.

Conclusions
There is a battle brewing in the US $600 range balanced DAC and headphone amplifier. The companies are doing well have one thing in common: they post proper audio precision measurements and the Singxer SDA-2 is no exception. No wonder then that it did so well on my tests in general.

As with its competitors, it is a hair off from perfection. The increased distortion in low frequencies is odd and should be investigated. Perhaps my model is different than the version they tested since its headphone amplifier section clearly has lower and better output impedance.

In practice, the SDA-2 is a pleasure to operate, gives a feeling of professionalism by its looks, and sounds fantastic with ample amount of power. As such, it is my pleasure to add the Singxer SDA-2 to my recommended list.

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

We have a mountain of apples and pears form our orchard that we need to can so we eat well in winter. Need money for supplies to can them all. Appreciate you all donating money using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

JohnYang1997

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#6
Is it time to use the DX7 Pro as the reference on the charts? Also seems more relevant at this price point as well. The differences between these two are intriguing.
It's better to get something good but not best for reference. So that we can see where we are in the performance. If you choose best performance then all new measurements are going to be on par or worse. The choice of the reference is less of the pricing but a good reference to see where we are.
 

anmpr1

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#8
I am happy to see a mid-priced options that are close to SOA. I think these products could do a lot to turn the general perception of Chinese gear around. Reminds me of mid level hi-fi gear from Japan in the '60s and '70s (Sony, Yamaha, Pioneer, Teac, Kenwood, Sansui and the others). Those changed some long held perceptions of that country's electronics. Especially since many of those are no longer in the serious consumer hi-fi business.
 

amirm

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#9
BTW, one feature this DAC has is galvanic isolation on its input. So it should not be susceptible to ground loops nearly as much.
 

Labjr

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#11
Galvanic isolation is nice to have. If it's optional, he'd have to test that version of the DAC before recommending it. There's always that one new feature that makes you wonder what the next DAC is going to add?
 

Patrick1958

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#12
Was reading the specs some time ago for the SDA-2 and was put of because of the headphone output impedance saying : 22 Ohm SE, 44 Ohm Balanced. Did Singxer upgraded the unit's hardware (that Amir measured) or are webshops giving wrong specifications?
 

Wombat

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#13
Confusing supply voltage labelling and different rear panels.

Singxer-SDA-2-DAC-DAC-and-Headphone-Amplifier-Back-Panel-Connectors-Review.jpg




singxer-sda-1-dac-ak4490-i2s-xmos-32bit-384khz-dsd512-dop.jpg
 
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amirm

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#14
Was reading the specs some time ago for the SDA-2 and was put of because of the headphone output impedance saying : 22 Ohm SE, 44 Ohm Balanced. Did Singxer upgraded the unit's hardware (that Amir measured) or are webshops giving wrong specifications?
I included the verbiage from their website on my graph. It says "less than 10 ohm" for 1/4 inch and "less than 20 ohm for XLR" now.
 

Fred Jacquot

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#17
@amirm, ref comparison with DX3 pro, DX3 pro uses AK4493, SDA-2 uses AK4497. Not exactly the same chip (even if anecdotical).
 
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Jimster480

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#19
This looks nice, but it would be a hard sell over the DX7 Pro which is 15% cheaper and performs better.
I guess if you want to have the lower output impedance?
 
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