• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

SMSL SU-1 Stereo DAC Review

Rate this DAC:

  • 1. Poor (headless panther)

    Votes: 8 1.8%
  • 2. Not terrible (postman panther)

    Votes: 9 2.0%
  • 3. Fine (happy panther)

    Votes: 56 12.3%
  • 4. Great (golfing panther)

    Votes: 381 83.9%

  • Total voters
    454

ManniX

Active Member
Forum Donor
Joined
May 13, 2023
Messages
120
Likes
52
Location
Germany/Italy
Although the THD is still excellent I just wonder why I have so much noise ? The noise cannot comme from the ADC nor the computer because it was good on optical with the same other connections, I mean USB powered on the desktop on the SU1 and USB powered by laptop on the ADC.

AFAIK Optical SPDIF is immune to grounding noise, while USB isn't.
Do you have another USB DAC to compare against with a THD+N supposedly below -95 dB?
I see you brought the USB-C splitter cable but mind that it will only remove grounding noise coming from the power pins.
If your computer is not properly grounded or there's AC noise it will still end up in the SU-1 via the data pins.
 

Abrise

Member
Joined
Apr 25, 2023
Messages
61
Likes
89
Location
French Expat in Bangkok
AFAIK Optical SPDIF is immune to grounding noise, while USB isn't.
Do you have another USB DAC to compare against with a THD+N supposedly below -95 dB?
I see you brought the USB-C splitter cable but mind that it will only remove grounding noise coming from the power pins.
If your computer is not properly grounded or there's AC noise it will still end up in the SU-1 via the data pins.
I have nothing that good. My old dacs of 10 to 15 years old are 85dB and 75db THD+N. The 3 DAC curioulsy have the same noise of 100 to 102dB. I was expecting that a modern DAC would filter this noise.
 

Abrise

Member
Joined
Apr 25, 2023
Messages
61
Likes
89
Location
French Expat in Bangkok
I have nothing that good. My old dacs of 10 to 15 years old are 85dB and 75db THD+N. The 3 DAC curioulsy have the same noise of 100 to 102dB. I was expecting that a modern DAC would filter this noise.
I forgot that I also have a Focusrite solo. I just measure it and it is much better. Its noise is only 112db although it is also a USB dac.
So why the others are not doing as well as Focusrite ?
1684677962790.jpeg
 

ManniX

Active Member
Forum Donor
Joined
May 13, 2023
Messages
120
Likes
52
Location
Germany/Italy
I forgot that I also have a Focusrite solo. I just measure it and it is much better. Its noise is only 112db although it is also a USB dac.
So why the others are not doing as well as Focusrite ?

My guess is the Focusrite is just better isolated internally.
And a good design doesn't matter if it's old or new.

Did you try grounding the PC and/or the DAC?
If you have a radiator nearby you can connect the PC case and the DAC chassis to it.

Otherwise you may need a decent power conditioner but if you go that way it's better something you can return.
Very often even the good ones are totally ineffective. Depends on the kind of noise.
 

Abrise

Member
Joined
Apr 25, 2023
Messages
61
Likes
89
Location
French Expat in Bangkok
My guess is the Focusrite is just better isolated internally.
And a good design doesn't matter if it's old or new.

Did you try grounding the PC and/or the DAC?
If you have a radiator nearby you can connect the PC case and the DAC chassis to it.

Otherwise you may need a decent power conditioner but if you go that way it's better something you can return.
Very often even the good ones are totally ineffective. Depends on the kind of noise.
Thank you for your suggestions. I think that I have anyway enough usb to spdif devices that are solving the problem anyway.
This morning I tested again on USB and get very good results with -122dbfs of noise for my SU1 but 1 hour later tested again and I was back to -99 dbfs . Also I noticed that if I plug the usb C wire one way the unit is not recognized by windows and plug it the other way it is recognized. I already threw away a few cables because ot the SU1. But it is possible that the USB input of the SU1 is damaged or deficient not the cables.
 

ManniX

Active Member
Forum Donor
Joined
May 13, 2023
Messages
120
Likes
52
Location
Germany/Italy
Thank you for your suggestions. I think that I have anyway enough usb to spdif devices that are solving the problem anyway.
This morning I tested again on USB and get very good results with -122dbfs of noise for my SU1 but 1 hour later tested again and I was back to -99 dbfs . Also I noticed that if I plug the usb C wire one way the unit is not recognized by windows and plug it the other way it is recognized. I already threw away a few cables because ot the SU1. But it is possible that the USB input of the SU1 is damaged or deficient not the cables.

Yes, using SPDIF is definitely easier. But you need to live with the bandwidth limitations...

If you didn't change anything after the 2nd test of the SU1 then it's probably AC noise.
In general USB ports/cables when defective/low quality they are always generating noise/issues or very random.
This looks more something like a fridge compressor that when is running will pollute otherwise not.

Note that USB-C cables are reversible only mechanically.
Electrically they aren't.
One side has the RX and the other TX.
You can flip it but you are also swapping the direction of data transmit.

Cheap (or supposedly high quality but truly cheap) cables have only one direction running at full speed.
Best way to test a USB cable is a USB SSD running at about 1000 MB/s, 10 Gbps.
Of course you need a PC with a 10 Gbps USB port.
Once you know the reference speed of the drive (depends also on your PC how high it can go) you can compare the cables.

You need to take every time a reference benchmark with CrystalDiskMark, after you ran Optimize (Trim) from "Defragment and Optimize drives".
This will tell you if the USB in general is working and how fast can go.
Then you can plug the cable and evaluate the loss in speed and if it's really bi-directional or not.
If it's not bi-directional either the read or write speed will be cut in half or so.
I use a Samsung T7 which is the most reliable and compatible for this job. Better if the 1TB version.

But indeed could also be the SU1 USB port is defective.
 

Abrise

Member
Joined
Apr 25, 2023
Messages
61
Likes
89
Location
French Expat in Bangkok
Yes, using SPDIF is definitely easier. But you need to live with the bandwidth limitations...

If you didn't change anything after the 2nd test of the SU1 then it's probably AC noise.
In general USB ports/cables when defective/low quality they are always generating noise/issues or very random.
This looks more something like a fridge compressor that when is running will pollute otherwise not.

Note that USB-C cables are reversible only mechanically.
Electrically they aren't.
One side has the RX and the other TX.
You can flip it but you are also swapping the direction of data transmit.

Cheap (or supposedly high quality but truly cheap) cables have only one direction running at full speed.
Best way to test a USB cable is a USB SSD running at about 1000 MB/s, 10 Gbps.
Of course you need a PC with a 10 Gbps USB port.
Once you know the reference speed of the drive (depends also on your PC how high it can go) you can compare the cables.

You need to take every time a reference benchmark with CrystalDiskMark, after you ran Optimize (Trim) from "Defragment and Optimize drives".
This will tell you if the USB in general is working and how fast can go.
Then you can plug the cable and evaluate the loss in speed and if it's really bi-directional or not.
If it's not bi-directional either the read or write speed will be cut in half or so.
I use a Samsung T7 which is the most reliable and compatible for this job. Better if the 1TB version.

But indeed could also be the SU1 USB port is defective.
Your comments on USB C are very interesting. I have just ordered 2 days ago a few cables. Maybe I should have bought more expensive ones . I'll test when they arrive.
 

ManniX

Active Member
Forum Donor
Joined
May 13, 2023
Messages
120
Likes
52
Location
Germany/Italy
Your comments on USB C are very interesting. I have just ordered 2 days ago a few cables. Maybe I should have bought more expensive ones . I'll test when they arrive.

Expensive doesn't help sadly... see below.
Also avoid anything that has active components inside.

Well, I take it back that the Samsung T7 is reliable.
Wanted to get a couple of benchmark examples and found out the drive is failing, write speed went down to 15-300 MB/s.

I had to use the Crucial X8 which is a very performant drive but not as good as the T7.
First it comes with a faulty USB-C cable... only a straight USB-C cable and you have to replace it.
The T7 comes with 2 very high quality cables, one straight USB-C the other USB-A to C.
The X8 gets also very hot and does not have any power management function so it stays hot even in idle and consumes power without any reason.
But it has proven, so far, more reliable than the T7.

Here's the reference benchmark for the X8, connected straight with a high quality USB-C cable (very thick, usually a good sign):

1684751224348.png


This is using an unknown old USB-A 3.0 extension cable and a good USB-A to C cable (which I think is the 2nd cable that came with the T7):

1684751639093.png


This is what you want to see from another cable or an extension cable.
It's not going to ensure that the cable is noise or problem free but it's a good indication the risk is minimal
This is the connection I'm using right now for the PO100 AK DAC.

Keep in mind that even if most (if not all?) DAC are USB 2.0, it's important the cable works flawlessly at USB 10G.
Means it's high quality, more than needed, and the DAC should easily work constantly without any issue.

This is the cable I actually bought for the DAC and found out it was absolute trash.
An awesome "Premium" cable 3 meters USB-A to C rated at 5GBps.
It randomly switch to USB 2.0 data rate or USB 2.0 only for TX or worse...

1684751933058.png


1684753297852.png


This cable is guaranteed it will drive you mad...
(Note that the unusual speed of RND4K Q32T1 is due to PrimoCache RAM caching on this OS)

This is what you have to expect as data rate drop using a in between Hub:

1684753399114.png


Another example, about expensive cables, is this one.
This is a Yottamaster extension cable at 20G which I used almost a year with the hub above.
It's a 20€ cable which is quite expensive for the usual Chinese almost no-name brand.
Not a single issue until recently when it decided to fail...

1684753499722.png


It was able to support the hub above which is a 20G at almost full speed testing both the SSDs in parallel.

So always test your cables, hope for the best when you order and regularly test them to be sure they are not suddenly failing.
Reading reviews on Amazon doesn't help cause most of these brands, also the well known, are changing fabs every now and then.
Thus the quality of the cables depends on the supplier at the time and could be worse or better than expected.

Certified USB-IF cables are almost impossible to find, difficult to identify, extremely expensive.
Most of them are not really certified while claiming they are.
Even when they are really USB-IF certified but cheap, like the Amazon branded cables which I bought to test, they are scrap and they fail exactly like other cheap cables.
Best strategy; buy many, test them, send them back if not worth.
 

HappyMetalGuy

Active Member
Joined
Jul 13, 2022
Messages
150
Likes
110
Location
Portugal
Your comments on USB C are very interesting. I have just ordered 2 days ago a few cables. Maybe I should have bought more expensive ones . I'll test when they arrive.
Are you using the Y splitter cable from aliexpress? does it make any difference?
 

Abrise

Member
Joined
Apr 25, 2023
Messages
61
Likes
89
Location
French Expat in Bangkok
Are you using the Y splitter cable from aliexpress? does it make any difference?
I can use it with the E1DA where it doesn't make a siginificative difference. I cannot use it with the SU1 because my power bank doesn't provide enough voltage to power it.

I have received new USB cables today they work but still windows recognize the SU1 only on one face of the USB C confirming C is not reversible !

My main issue of noise with the desktop computer is solved thanks to more careful procedure. I have lost hours because of a stupid tick in a software. This is shameful but I can say it. Until now I never had to deal with such good devices sas the SU1 and E1DA and the mistake was thus not visible. "Add dither " reamained ticked in the generator window. 16 bits was selected. Putting 24 bits or unselecting it eliminates the noise. 16 bits dither was thus the culprit of the -100dbfs noise ; it is now below -120dBfs.
The thing is that at the beginning I really had grounding issues with another dektop computer internal card. And I stayed focused on this type of problem instead of being more careful.
No good excuse anyway of not doing measurement carefully.
 

ManniX

Active Member
Forum Donor
Joined
May 13, 2023
Messages
120
Likes
52
Location
Germany/Italy
Well, glad you found the culprit!
Hope you can delight us with some testing results now :p

You could still check if there's an improvement with the Y-cable by decoupling the PC and using a decent USB PSU to power the DAC instead of a powerbank.
 

HappyMetalGuy

Active Member
Joined
Jul 13, 2022
Messages
150
Likes
110
Location
Portugal
I cannot use it with the SU1 because my power bank doesn't provide enough voltage to power it.

I have received new USB cables today they work but still windows recognize the SU1 only on one face of the USB C confirming C is not reversible !
You can power the SU-1 from a phone charger. My Windows PC recognizes SU-1 with every cable and also reversed.
 

HappyMetalGuy

Active Member
Joined
Jul 13, 2022
Messages
150
Likes
110
Location
Portugal
Yes I have tried 3 different windows pc and a lot of cables including a C to C, it always work only one way.
The usb it's definitely damaged, you should return your unit. My unit was bought on 22/04 from amazon.de and I still have until 31/05 to return it.
 

Abrise

Member
Joined
Apr 25, 2023
Messages
61
Likes
89
Location
French Expat in Bangkok
The usb it's definitely damaged, you should return your unit. My unit was bought on 22/04 from amazon.de and I still have until 31/05 to return it.
Ypu are definitely right, I should return it but going bazck to china Shenzenaudio and return to my country it will take 1 month. And I need this unit for a few test I want to make before deciding if I am going to change my equipments. The unit works with this small limitation. And it is only 74€
 

HappyMetalGuy

Active Member
Joined
Jul 13, 2022
Messages
150
Likes
110
Location
Portugal
Ypu are definitely right, I should return it but going bazck to china Shenzenaudio and return to my country it will take 1 month. And I need this unit for a few test I want to make before deciding if I am going to change my equipments. The unit works with this small limitation. And it is only 74€
If it measures well like @amirm you just have to mark the right side of the usbc cable and you're done, mine was 80€ perfect find.
 
Top Bottom