SMSL SU-1 Stereo DAC Review

[Luisinky]

I recently purchased the SU-1 and use in conjuction with a Bluesound Node connected by USB. I have TIDAL source and no issues streaming, but I am a bit confused by the MQA lights.
GREEN: streaming or files in MQA format.
BLUE: Playing in MQA studio file.
MAGENTA: Delivering final unfold of MQA file and displays the original sample rate.
I see the green light at times and blue light other times during playback and unsure what is happening. The tiny manual is really no help. Any thoughts?

 

[RJHJR]

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!

I haven't measured mine yet (don't have a sensitive enough meter) but the output certainly is low. I replaced another DAC with this (between Echo Link and 48 Volt Fosi V3) using the same cables and the volume is significantly lower.
I'm using at least 50% higher volume setting on the V3 to approach previous sound level. I've tried using different 5V supplies, optical and coaxial inputs without change. I take it there is no adjustment that can be made.

 

[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!

To confirm, I measured the DC offset voltage of the two SU-1s I'm currently using, and they were 3.1mV/2.8nV and 0.8mV/0.7mV. This is a sufficiently low value.

 

[Philipp]

To confirm, I measured the DC offset voltage of the two SU-1s I'm currently using,

Yeah, sorry, already thought that my „measurements“ are to good to be true, low-pro-equipment, but on the other hand, sufficient to detect dangerously high DC-offset, which there is none.
Thanks for confirming @Toku !

 

[ninetylol]

Does the SMSL SU-1 got hardware volume control under windows usb?

You could check this in driver control panel or if volume changes under WASAPI when you change windows volume.

 

[Azzazin]

Getting annoying clicks and pops when starting and pausing audio with this dac. I’m on Mac. How do i solve this problem?

 

[TNT]

Correct, referring to this text. In Amir‘s multitone measurements we see a spike next to 6kHz. I also assume the PS could be anemic. The SU-1 seems to use only 0.1 uF. I would like to know whether such a large capacitance can be used after DC to DC upconversion (and switching of polarity). Unfortunately I cannot identify the parts that convert USB-power to +/-12V. Maybe the converter circuit is hidden in the “brick” close to the outputs?

Did you pursuit this? I suppose one should place the 10uF as close to the op amps as possible and not at the PS end. As such, you don't need to find the PS ;-) just the OP-amp...

I would / will use a non polar high quality cap myself - Wima....

I wonder what the circuit that is marked with the orange star - a turn on bloop mitigater?

//

 

[Herbert]

Hm-I do not find in the datasheet that TI recommends a capacitor between the positive and negative voltage rail:

https://www.ti.com/lit/ds/symlink/lme49720.pdf?ts=1702570586634&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLME49720

 

[radix]

Did you pursuit this? I suppose one should place the 10uF as close to the op amps as possible and not at the PS end. As such, you don't need to find the PS ;-) just the OP-amp...

I would / will use a non polar high quality cap myself - Wima....

I wonder what the circuit that is marked with the orange star - a turn on bloop mitigater?

View attachment 333778

you are referring to text like this:

11.1 Power Supply Decoupling Capacitors The LME49720 requires adequate power supply decoupling to ensure a low total harmonic distortion (THD). Place a low equivalent-series-resistance (ESR) ceramic capacitor, typically 0.1 µF, within 2 mm of the V+ and Vpins. This choice of capacitor and placement helps with higher frequency transients, spikes, or digital hash on the line. In addition to the 0.1 µF ceramic capacitor, it is recommended to place a 2.2 µF to 10 µF capacitor on the V+ and V- pins. This larger capacitor acts as a charge reservoir, providing energy faster than the board supply, thus helping to prevent any droop in the supply voltage.

That should be a 2.2-10 uF between V+ and GND and V- and GND, not between V+ and V-. This "charge reservoir" is highly dependent on the board layout, trace width, and other factors. If the traces are OK and there's not other things dropping voltage on the line, it might be just fine with the supply caps farther away. This is very different than noise decoupling caps. Personally, I doubt that for audio frequencies it matters, but I've not run any numbers.

There are some designs that use one decoupling capacitor between V+ and V-, but I think those only apply if the output signal is not referenced to ground.

 

[TNT]

@radix

In the data sheet TI suggest some ideas around layout. Why do they show -V (p4) to ground when the spec seems to imply a +/- power need? Or is is kino of "not complete..."

//

 

[radix]

@radix

In the data sheet TI suggest some ideas around layout. Why do they show -V (p4) to ground when the spec seems to imply a +/- power need? Or is is kino of "not complete..."

View attachment 334378

//

It is perfectly valid to run the rails 0 to V+. Maybe it's not audio? Or maybe they have it at a DC offset. The data sheet tries to cover many use cases. An engineer still needs to design the actual circuit. The data sheet is for illustration and explaination.

 

[TNT]

Yes I realised that as I read on. Thanks!

//

 

[Honu]

Lol...?

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.

Usb-C are perfextly reversible, Tx and Rx, are swapped both ways.

 

[Tangband]

To confirm, I measured the DC offset voltage of the two SU-1s I'm currently using, and they were 3.1mV/2.8nV and 0.8mV/0.7mV. This is a sufficiently low value.

Good to know ! No problem using Hypex ncore then .
Is there any conclusion yet if this dac will gain in soundquality with a better external power supply than an ordinary phone charger ? I got this lm317 LPS powering my WiiM pro right now.

 

[Tangband]

So, on an old 30 mHz scope:
The SPDIF without transformer, terminated to 75 ohm:
View attachment 313350
And with the transformer inserted:
View attachment 313351
God? Bad?
But the cable, about 1.5m, is not a dedicated 75-ohm BNC-cable but some yellow RCA Video cable taken from a camera...

A transformer is always better than without when using spdif, it isolates the digital sender from the dac input. This is much more important than other issues using the spdif transformer, as you have shown.

An example where it should be used is between a WiiM pro ( no transformer used ) and this SMSL su1 ( no transformer on spdif input ) . This means theres a potentional risk that polluted ground might be on both the WiiM and the SU1.

Edit: As onlyoneme has shown with measurements, the electrical digital output of the Wiim pro is slightly polluted and modulated by the mains If using the stock supply. The spdif is good but not perfect. Onlyoneme has also shown that using a battery power supply , the output is slightly cleaner without any mains modulation.

WiiM Pro Plus - Review & Measurements (Streamer)

The scale is totally different. You need to look at the same site to make sure that the method and measuring equipment is the same yes the scale of what I show is much harder ;-)

www.audiosciencereview.com

Of course this potential issue is a non issue using toslink .

 

[Guilherme_BR]

It seems to measure better than Denafrips Terminator Plus?

 

[Toku]

It seems to measure better than Denafrips Terminator Plus?

Based on the measurement results of ASR's R2R type DAC so far, I think the SU-1 has probably better measurement results. However, the prices of the two are nearly 100 times different, and the manufacturing quality of Terminator Plus is by far superior.
I think that the evaluation of such expensive equipment is not just a comparison of numerical data, but a comparison on a completely different dimension. The beautiful finish, the joy of looking at it, the unique sound quality, etc.
The evaluation will be completely different depending on what you want from the product.
It's like comparing a tube amp to a class D amp.

As an engineer, the more I research this product, the more I am drawn to its splendor as an industrial product. When I look at products like this, I start to think that I don't care about measurement numbers.

 

[Guilherme_BR]

Based on the measurement results of ASR's R2R type DAC so far, I think the SU-1 has probably better measurement results. However, the prices of the two are nearly 100 times different, and the manufacturing quality of Terminator Plus is by far superior.
I think that the evaluation of such expensive equipment is not just a comparison of numerical data, but a comparison on a completely different dimension. The beautiful finish, the joy of looking at it, the unique sound quality, etc.
The evaluation will be completely different depending on what you want from the product.
It's like comparing a tube amp to a class D amp.

As an engineer, the more I research this product, the more I am drawn to its splendor as an industrial product. When I look at products like this, I start to think that I don't care about measurement numbers.

But do you think there's a rational reason to buy a 10000 R2R DAC based purely on sound performance? Spatial presentation, maybe?

 

[Toku]

But do you think there's a rational reason to buy a 10000 R2R DAC based purely on sound performance? Spatial presentation, maybe?

For me, the appeal of the 10000 R2R DAC is the beauty of the finish as an industrial product. High quality cases, PC substrates with beautiful layouts. If this product is $ 1000, I may buy it, but it doesn't feel attractive as an audio equipment. I am satisfied with the two SU-1 and E30 ll I am using now.

 

[G-Can]

I returned SU-1 and got C100 because I need remote. I don't really hear any difference.