This is a review and measurements of the SMSL X-USB. It is a very small form factor USB to S/SPID, Toslink optical and I2S (using mini-HDMI connector). It is on kind loan from a member.
When I say small form factor, I mean it. Here is a comparison of it to a couple of DACs I have:
Even smaller is its display as you can (barely) see in the picture. Still, I like to have that than nothing.
Heavy cables are going to drag this around but maybe with the small size you can tape it to back or top of your DAC.
Retail price that I see as of this writing is around $89 plus shipping so close to $100.
The purpose of this product is to bring USB connectivity to older DACs without such an input. Alternatively if your DAC has a poor performing USB input, you can use these devices to improve their performance assuming they also have S/PDIF input.
Let's do some measurements and see how it does. As usual, if you are not familiar with what these graphs are, refer to my tutorial on understanding audio measurements: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/
Measurements
Our weapon of choice here is the J-Test signal which brings out jitter and noise out of the DAC. For a DAC to test, I first started with Topping D50 but there was little difference of note there. So I tested with Schiit Uber 2 (review to come in the future). Here there were clear differences between the three devices under test.
First, let's see how the Schiit Modi 2 Uber does with its own USB interface and then driven via SMSL X-USB using its S/PDIF input:
The "naked" Modi 2 Uber is in yellow. We see some spikes below 2 kHz which I happen to know comes out of my HP laptop USB bus. In addition there is random low frequency jitter which explains the broad "skirt" around our main 12 kHz tone in the source.
Addition of SMSL X-USB nicely cleans up the < 2 kHz spikes but unfortunately adds its own spikes a pair of which I have marked with the green cursor. While not an audible concern due to its low level, nevertheless it is not good engineering. Like there are oscillators running elsewhere in the device bleeding into the S/PDIF clock.
The Random jitter (in yellow) is left unchanged with indicates this is a problem in the DAC itself and not as a result of USB interface.
Next let's see what happens if we use my now ancient Audiophilleo USB to S/PDIF converter:
I say good engineering last and here is a great example of it. The Audiophilleo eliminates the low frequency noise and distortions from Modi 2 Uber without introducing any distortions of its own. It is a clear win over the SMSL X-USB.
I also made a comparison using the Gustard U-12 which I reviewed a while back:
As we see, the Gustart also does well matching Audiphilleo's performance while not introducing its own noise products.
Conclusions
The SMSL X-USB is small and attractively priced for a USB to S/PDIF converter. Alas, its performance is not satisfactory. Internal circuits leak noise onto the S/PDIF clock causing new distortion spikes while some cleaning of lower frequency USB noise is performed. Audibly these are benign so if you like the form factor and attractive price, it would make a decent purchase. Otherwise if you can spend a bit more and get the Gustard U12 ($169 including Amazon Prime shipping), it is a better performing unit.
As always, questions, comments, corrections, jokes, etc. are all welcome!
----
If you like this review, please consider donating funds for these types of hardware purchase using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
When I say small form factor, I mean it. Here is a comparison of it to a couple of DACs I have:
Even smaller is its display as you can (barely) see in the picture. Still, I like to have that than nothing.
Heavy cables are going to drag this around but maybe with the small size you can tape it to back or top of your DAC.
Retail price that I see as of this writing is around $89 plus shipping so close to $100.
The purpose of this product is to bring USB connectivity to older DACs without such an input. Alternatively if your DAC has a poor performing USB input, you can use these devices to improve their performance assuming they also have S/PDIF input.
Let's do some measurements and see how it does. As usual, if you are not familiar with what these graphs are, refer to my tutorial on understanding audio measurements: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/
Measurements
Our weapon of choice here is the J-Test signal which brings out jitter and noise out of the DAC. For a DAC to test, I first started with Topping D50 but there was little difference of note there. So I tested with Schiit Uber 2 (review to come in the future). Here there were clear differences between the three devices under test.
First, let's see how the Schiit Modi 2 Uber does with its own USB interface and then driven via SMSL X-USB using its S/PDIF input:
The "naked" Modi 2 Uber is in yellow. We see some spikes below 2 kHz which I happen to know comes out of my HP laptop USB bus. In addition there is random low frequency jitter which explains the broad "skirt" around our main 12 kHz tone in the source.
Addition of SMSL X-USB nicely cleans up the < 2 kHz spikes but unfortunately adds its own spikes a pair of which I have marked with the green cursor. While not an audible concern due to its low level, nevertheless it is not good engineering. Like there are oscillators running elsewhere in the device bleeding into the S/PDIF clock.
The Random jitter (in yellow) is left unchanged with indicates this is a problem in the DAC itself and not as a result of USB interface.
Next let's see what happens if we use my now ancient Audiophilleo USB to S/PDIF converter:
I say good engineering last and here is a great example of it. The Audiophilleo eliminates the low frequency noise and distortions from Modi 2 Uber without introducing any distortions of its own. It is a clear win over the SMSL X-USB.
I also made a comparison using the Gustard U-12 which I reviewed a while back:
As we see, the Gustart also does well matching Audiphilleo's performance while not introducing its own noise products.
Conclusions
The SMSL X-USB is small and attractively priced for a USB to S/PDIF converter. Alas, its performance is not satisfactory. Internal circuits leak noise onto the S/PDIF clock causing new distortion spikes while some cleaning of lower frequency USB noise is performed. Audibly these are benign so if you like the form factor and attractive price, it would make a decent purchase. Otherwise if you can spend a bit more and get the Gustard U12 ($169 including Amazon Prime shipping), it is a better performing unit.
As always, questions, comments, corrections, jokes, etc. are all welcome!
----
If you like this review, please consider donating funds for these types of hardware purchase using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).