SMSL SU-1 Stereo DAC Review

[TNT]

Thanks.... AwdioNoob, maybe it is your PC actually? I'm planning to use it via Toslink so perhaps I may not run it to that problem that Took has...

//

 

[Tangband]

This is a review and detailed measurements of the SMSL SU-1 stereo USB DAC. It was arranged to be sent to me by shenzhenaudio from the company and costs US $79.99.
View attachment 280769
Despite its simplicity, the SU-1 manages to look elegant with nice fonts and LED indicators for different inputs. Back panel has the basically what you want:
View attachment 280770
My usual minor gripe applies here with right channel RCA not being red although in this case, it is easy to turn the unit around to plug in the cables. A USB-A to USB-C cable is provided. Note that you need to have a USB power supply even if you use non-USB input (it is the only source of power).

SMSL SU-1 Measurements
Let's start with our usual dashboard:
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Very nice performance with respect to noise and distortion, easily landing it in our "excellent" category of DACs:
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Zooming in:
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Full transparency is achieved not only for distortion but also noise:
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IMD distortion is basically non-existent with the performance limited by noise alone:
View attachment 280775

Jitter shows some negligible spikes of no audible concern at all:
View attachment 280776

Multitone shows extremely good performance:
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Linearity is almost perfect:
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Filter attenuation is very good:
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Resulting in good wideband noise+distortion measurement:
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Finally, frequency response is essentially flat in audible band:
View attachment 280781

Conclusions
SMSL cuts the functionality to minimum many need to have high quality conversion of digital to analog from multiple inputs. Performance is superb for the cost as it provides full transparency to the source. It proves that performance requires great engineering skill, and not a ton of money. A lesson that I hope one day high-end audio companies and their customers appreciate.

I am happy to recommend the SMSL SU-1. There is no more excuse for having bad DAC performance!

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

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Is there any dc on the output ?

 

[Toku]

In regards to the comments above with early problems ... my audio has stopped working 3 or 4 times in 2 weeks of daily use with the SU 1. Sometimes it stops after a song, other times when the PC goes to sleep. The only solution seems to be restarting the PC. Unplugging, powering off, or switching the audio source on the DAC has no effect.

The DAC is connected to a WiiM receiver via toslink. When the issue occurs, the OPTICAL indicator light on the DAC blinks.

What we can determine from the symptoms is that the Toslink signal has been interrupted and cannot be received by SU-1.
My guess is that the PC's USB selective suspend function worked.
No such symptoms occur on my two SU-1 Toslinks.

 

[radix]

I use the SU-1 via USB from a RPi 4 with Volumio 3 to an Anthem STR. I do not play DSD, only streaming services & internet radio and maybe a few local mp3/flac via roon. I've never had problems with the SU-1. The RPi 4 stays on pretty much all the time w/ the SU-1 powered up. Only the STR gets power off (standby).

P.S. I use this config because if I go Volumio 3 USB direct to the Anthem, it gets confused about the target going up/down and sometimes takes a while before it is ready to play.

 

[DSJR]

I reported that when I was continuously playing DSD files with the USU-1 connected to USB, the connection suddenly disconnected and playback stopped. Foober2000 displays the following message and stops playing.
"Unrecoverable playback error: Could not query channel counts"

Sorry to ask, why DSD?

 

[Toku]

Sorry to ask, why DSD?

I don't know why the symptoms only occur with DSD.
This is a common problem with DAC products, not just SMSL. I think the cause is probably the firmware of the XMOS chip. Firmware for XMOS such as the XU316 is not developed by manufacturers such as SMSL in-house, but is supplied by XMOS according to each company's specifications.
Therefore, manufacturers such as SMSL and Topping cannot pursue it deeply.

 

[AwdioNoob]

Thanks.... AwdioNoob, maybe it is your PC actually? I'm planning to use it via Toslink so perhaps I may not run it to that problem that Took has...

//

I have no idea. The rest of my setup is unchanged for many months/years. The audio issue only appeared after I added the DAC. And I only posted after I saw Toku's comment about playback stopping. Not here to rip SMSL ... I'd love to find a solution if the issues stems from my PC.

Next time the issue occurs, I will remove the DAC from the chain and see if that fixes it.

 

[Philipp]

Hello folks,
anyone knows if DC-offset is a problem with the SU-1? It appears to be a problem with some SMSL DACs but I did not come about any specific info about the SU-1.
Any help would be much appriciated!

 

[Toku]

Hello folks,
anyone knows if DC-offset is a problem with the SU-1? It appears to be a problem with some SMSL DACs but I did not come about any specific info about the SU-1.
Any help would be much appriciated!

Does DC-offset mean the DC potential of the RCA output?

 

[Philipp]

Yes.

 

[Toku]

The RCA output of SU-1 is directly connected to the output of the OP amplifier. Therefore, minute voltages can be detected as DC-offset. What offset voltage is your SU-1?

 

[IndieSynth]

Anyone know a way of stopping the annoying flashing light when no signal detected? I'd just like it to idle until I need it without it blinking at me

 

[radix]

Anyone know a way of stopping the annoying flashing light when no signal detected? I'd just like it to idle until I need it without it blinking at me

Electrical tape? I use that over all sorts of annoying LEDs.

Grey duct tape works as a significant brightness reducer, but you can still see the LED. Electrical tape is like a blackout curtain.

 

[Philipp]

@Toku
I measured it with a multimeter today, did not know how it has to be done, but thanks to ASR and JDSlabs I know now.
I hope I got it right, red probe to the inner pin, black probe to the sleeve.
Multimeter set to mV.

Results:
DC-offset does not to be an issue with the SU-1:
Unit off: 000,1 mV
Unit on but no music playing (no input): 000,1 mV
Turn on/off: 000,1 mV
while streaming music from Wiim Mini: up to 003,5 mV

Cheers!

 

[Toku]

@Toku
I measured it with a multimeter today, did not know how it has to be done, but thanks to ASR and JDSlabs I know now.
I hope I got it right, red probe to the inner pin, black probe to the sleeve.
Multimeter set to mV.

Results:
DC-offset does not to be an issue with the SU-1:
Unit off: 000,1 mV
Unit on but no music playing (no input): 000,1 mV
Turn on/off: 000,1 mV
while streaming music from Wiim Mini: up to 003,5 mV

Cheers!

That's an amazing number! There's no problem at all.

 

[Daviede]

Have you ever bought this compact DAC before? Does anyone like to directly connect their phone to SU1 using the TYPE C adapter cable? Mobile phone - SMSL SU1 Fosi audio V3

 

[Toku]

I previously reported that during continuous DSD playback tests on the SU-1, playback suddenly stopped and the connection to USB was disconnected.
For testing the DAC, I create a file that randomly arranges DSD64 to DSD512 and perform playback tests using it.
The files are arranged so that adjacent songs always have different sampling rates, but the SU-1 seems to occasionally make a mistake when switching the sampling rate.
However, I don't think there is any real harm because I don't think I would actually play a song file with this kind of arrangement.

 

[Toku]

Have you ever bought this compact DAC before? Does anyone like to directly connect their phone to SU1 using the TYPE C adapter cable? Mobile phone - SMSL SU1 Fosi audio V3

There is no problem with the connection, but the SU-1 probably won't work well when powered from a mobile phone. Also, connecting the SU-1 to a mobile phone will significantly drain the battery. There have been a number of reports that the SU-1 does not work properly even when connected to an iPhone or Android device, so it would be a good idea to investigate. It is better to consider connecting the SU-1 to a device with a reliable power supply, such as a PC's USB.

 

[Jazz]

Anyone know a way of stopping the annoying flashing light when no signal detected? I'd just like it to idle until I need it without it blinking at me

Black electrical tape. Harbor Freight has it cheap. If you have a hole punch, pop out a perfect circle. I just cut a little square.
I can’t imagine what caused the engineer to think users need to see a perpetual blinking light! Even for a dead signal. The lack of sound is the signal.

 

[Jazz]

I relented, and decided to ignore the MQA since, I never use it (and all audio gear eventually ends up partially or fully fossilized anyway with defunct gadgetry!) and bought one on sale.
It takes CD transports and lossless streaming to the next level. SMSL and AKM engineers and product leads deserve the high praise.