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Review and Measurements of SMSL SU-8 DAC

amirm

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#1
This is a review and detailed measurement/comparison of SMSL SU-8 DAC and Topping D50. It is on a kind loan from a member who had it drop shipped to me from Massdrop. Since there has been so much interest in this product, I decided to test it immediately.

Overall, the first impression is quite positive. Package is very nice and the unit has quite a heft and quality feel to it. It is a far more substantial unit than the Topping D50 due to inclusion of mains power supply and balanced outputs:

SMSL SU-8 vs Topping D50 Review and Measurements.jpg


The display is kind of tiny but does the job. It came with a remote which is a great bonus (I did not unpack it). The only minor gripe is the very short AC cable. I think it is 2 feet or something as opposed to typical 6 foot. So like me, you may need to supply your own.

The retail price is $249 with free shipping on US Amazon right now. I am assuming Massdrop price was lower. The Topping D50 is also $249 so if the SMSL SU-8 matches its performance, it is quite a bargain. Let's see how it did in measurements (all done with default filter setting).

Measurements
Let's start with Topping D50 so we have a good reference:
Topping D50 Dashboard Measurement.png


As noted, I powered the D50 using a Samsung charger I had laying around. Let's compare that to SMSL SU-8 using its unbalanced output:
SMSL SU-8 Unbalanced Dashboard Measurement.png


We see fair bit of power supply noise at 120 Hz and other harmonics of mains 60 Hz. We take a 4 to 5 dB hit in SINAD (signal above distortion+noise). Still, this is respectable performance with healthy output of over 2.1 volts.

There is fair bit of interest in balanced outputs of the unit so let's see how that did:

SMSL SU-8 Balanced Dashboard Measurement.png


Distortion climbs unfortunately reducing SINAD to 86 dB. As you see in this IMD graph, this is due to the output stage saturating:

SMSL SU-8 vs Topping D50 IMD Measurement.png


The balanced output in red clearly starts to saturate the output stage with distortion climbing past -7 dB or so. I guess if you keep the volume control down, you can reduce the impact of that.

Other than that, the performance of SMSL-8 SU-8 unbalanced output is pretty similar to Topping D50, both suffering from that mid-level "hump" courtesy of the ESS DAC chip used. Topping has slightly lower noise and distortion which we had seen in better SINAD numbers before.

Here is the spectrum of THD+N versus frequency:

SMSL SU-8 versus Topping D50 THD+N Measurement.png


This is done at 0 dBFS like the dashboard so obviously the balanced output does poorly with tons of distortion that gets worse with higher frequencies. I ran it again (not shown) at -5 dB and it was still worse than unbalanced (in red) but much more manageable.

The topping in green is well behaved with again, showing a bit less noise and distortion.

Here is a fun little graph/table I have started to show where each device lands with SINAD at 1 kHz:
Audio THD Measurement Table.png


We see a bucket of state-of-the-art on the left, then a mid-tier, and then the bottom on the right. Please remember that THD is not a very good measure of audibility so don't worry about small differences.

Finally, everyone's favorite measurement, linearity:

SMSL SU-8 Linearity versus Topping D50 Measurement.png


Here, tables turn and the balanced output of SMSL SU-8 (green) does much better than unbalanced (red). The Topping D50 as with other Topping products nails this test with perfect score.

Finally, here is the jitter and noise test:
SMSL SU-8 versus Topping D50 Noise and Jitter Measurement.png


Not much to note other than power supply noise in SMSL SU-8 on the left in red. And some USB packet noise in Topping D50 at multiples of 1 kHz and a couple of tones at 16 and 16.5 kHz. All inaudible due to their low level and our very high threshold of hearing at low and high frequencies.

Conclusions
The SMSL SU-8 seems to be a competently design DAC with superb feature set at an amazing price of $250. Some lack of hygiene exists which brings its measurements slightly below Topping D50. The other issue is the saturation of balanced output.

Overall, I am recommending this SMSL SU-8 to anyone who needs balanced output and in-built volume control with remote. It would make an excellent pairing with a couple of powered speakers like JBL 305.

-------------

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

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SIY

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#2
You already know my question;)- is the deviation from "linearity" because of actual deviation from linearity or is it from noise?
 

mi-fu

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#3
Thanks for the review, Amir.

I guess the biggest selling points of this are having a remote control and balanced output. How would you compare SU-8 to Topping DX7s, which I believe to be the closest, while more pricey, competitor?
 

amirm

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#4
Topping has headphone output which this one doesn't. It also has front-panel rotary control. So different functionality. If you don't need either, I am Ok with someone buying the SU-8. :)
 

gvl

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#5
Hmm, looks like one who's using a balanced pre/amp with its own volume control should not bother.
 

mindbomb

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#9
It looks like it has the same unbalanced linearity issue that the dac 3 had.

This dac has a 230v input switch iirc. Would people in that region be less affected by the clipping on balanced?
 
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amirm

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#10
This dac has a 230v input switch iirc. Would people in that region be less affected by the clipping on balanced?
No because internal voltage is regulated DC at much lower voltage and is independent of the AC input voltage.
 

Ron Texas

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#11
Another great set of measurements. Many make a big deal about balanced outputs. My take is they only offer resistance to noise on really long interconnects, 25' or more.
 
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#12
Great review and measurements, and just a day after I register here!

Unfortunetly, the device is pretty large compared to the D50 (and a bit less atractive than the Topping too, IMO), so I think my purchase decision is easiler now...

Anyway, I would like to ask if the balanced outputs have a tangible benefit for a normal user (who mostly uses headphones at close range) that I'm ignoring right now or it's fine to go just with the unbalanced ones in the D50.
 

Jimster480

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#13
Great review and measurements, and just a day after I register here!

Unfortunetly, the device is pretty large compared to the D50 (and a bit less atractive than the Topping too, IMO), so I think my purchase decision is easiler now...

Anyway, I would like to ask if the balanced outputs have a tangible benefit for a normal user (who mostly uses headphones at close range) that I'm ignoring right now or it's fine to go just with the unbalanced ones in the D50.
Balanced offers no benefit to headphones.
They are made to be used in long cables for pro speaker setups, and not used for headphones.
 

amirm

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#14
If you have a headphone amplifier with balanced inputs, then it may help with ground loops and such. Otherwise it is not needed.
 

gvl

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#15
If you have a headphone amplifier with balanced inputs, then it may help with ground loops and such. Otherwise it is not needed.
Helps to reduce mains leakage too, the graphs show it clearly.
 
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#16
Balanced offers no benefit to headphones.
They are made to be used in long cables for pro speaker setups, and not used for headphones.
That's what I've been read (and understood).

If you have a headphone amplifier with balanced inputs, then it may help with ground loops and such. Otherwise it is not needed.
Interesting.

But how much concern involves the ground loops in an unbalanced set-up (like the D50 with regular amplifier like my Magni 3) vs a balanced DAC and a proper amplifier with balanced inputs? Is there an audible difference?
 

amirm

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#17
But how much concern involves the ground loops in an unbalanced set-up (like the D50 with regular amplifier like my Magni 3) vs a balanced DAC and a proper amplifier with balanced inputs? Is there an audible difference?
The complications come from connection to the computer and long chain of ground from the computer to DAC and amplifier. To the extent your setup is quiet when you pause the music, then you are good to go and you don't need balance.
 

gvl

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#18
Balanced can in theory improve SnR due to higher voltage and reduction of mains hum from less than ideal power supply implementations. If the su-8 wasn't clipping over balanced you'd get higher SINAD over balanced than single-ended.
 
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#19
The complications come from connection to the computer and long chain of ground from the computer to DAC and amplifier. To the extent your setup is quiet when you pause the music, then you are good to go and you don't need balance.
So, it's basically what @Jimster480 says, right?

Crystal clear explanation for a newbie, many thanks. :)
 
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#20
Balanced can in theory improve SnR due to higher voltage and reduction of mains hum from less than ideal power supply implementations. If the su-8 wasn't clipping over balanced you'd get higher SINAD over balanced than single-ended.
Yeah, seems that way.

Although even in balanced, it cannot match the D50 performance...
 

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