Introduction

S.M.S.L is short for Foshan ShuangMuSanLin technology Co. Ltd., and is an audio brand founded in 2009 in China, with another branch (VMV) based out of Hong Kong since 2013. Between the two, S.M.S.L—henceforth referred to here as SMSL for convenience—has put out a long line of audio sources including DACs, power/integrated amplifiers, and headphone amplifiers with internal R&D and manufacturing. We saw SMSL's take on a more budget-entry DAC/amplifier stack with the SU-6 and SH-6 combo review late last year. I mentioned back then that the SU-6 DAC offered features that made it a more compelling offering relative to the direct competition from the likes of TOPPING and JDS Labs, even if it cost slightly more. Indeed, the $100 price point for DACs remained open from SMSL so I was not surprised that an even more affordable DAC was in the works.


Today we take a closer look at the SMSL SU-1 DAC with the lower number in the product name indicating this is the entry level DAC in the lineup. It's smaller than you might think looking at that photo above—comparable to some larger portable DAC/amps—but is still a desktop class device owing to the more extensive I/O as well as the need to hook it up to a headphones amplifier for desktop use. SMSL goes with AKM this time instead of ESS and also manages to get the dubious distinction of being likely among the last products ever to support MQA playback. I'll not talk about MQA thus although do be aware that this has no doubt contributed to the cost of the device. Thanks to SHENZHENAUDIO for providing a review sample to TechPowerUp as we begin this quick look with the product specifications in the table below. Be sure to click the image twice to fully open it and go through all the details.

Packaging and Accessories

I knew going in that the SMSL SU-1 was not a flagship product and yet I was surprised at how small the product box is. SMSL uses a predominantly white cardboard box with black accents to call out the product name in addition to the company logo, the now-expected Hi-Res Audio logo, and a render of the product on the front. Product certification and contact information for SMSL is seen on the box too, in addition to a sticker confirming the exact color of the unit inside.


The box has side flaps which open up to reveal a thick foam sheet, and an even thicker foam lining with compartments to fit and protect the various items included with the SU-1. This includes a warranty card with the SU-6, as well as a multi-language user manual that walks you through initial setup and use of the DAC. Given the diminutive nature of the DAC, we don't get an external power supply or even an AC mains power cable, instead SMSL goes for USB power and data alike with a USB Type-C to Type-A cable included to wrap up the unboxing experience.

Closer Look and User Experience

At 96 x 78 x 27 mm, the SMSL SU-1 DAC occupies about the same space on your desk as the likes of the FiiO Q11 and certainly less volume than the FiiO Q7, both of which are portable DAC/amps. Indeed, it's only with the ~200 g mass that you really come to terms with this being a desktop DAC even if you can probably carry it in the palm of your hand easily. As with other such SMSL products, the housing is made of CNC-machined anodized aluminium alloy given a durable black finish that is fairly resistant to smudges and fingerprints alike. The rounded edges and chamfers also help make this more than just a simple metal box, although personally I would have rather seen the Hi-Res Audio badge on the side or bottom rather than on the top. The form factor is more horizontal than vertical and the front panel extends outward from the body itself as seen above. Here we see the company and product names on the right, playback indicators lights towards the right with clear markings below, and then a physical switch for power/input selection all the way to the right. A sticker on the underside provides certification info and the serial number of your unit and we also see four round rubber feet at the corners to help add friction against your desk in addition to preventing scratches to the metal housing.


The back has a recessed panel where we see the physical connectors present. I wasn't expecting a lot of input options and yet SMSL impressed with not only USB—via Type-C, if only everyone went this route rather than Type-B—as well as coaxial and optical inputs. The USB input is also used to power the device so the provided cable will be necessary even if you go with the other inputs. Outputs come in the form of a set of single-ended RCA connectors that head out to your headphones amplifier; these also offer line-out.


There are screws on the back used in the assembly of the SMSL SU-1, which I promptly removed after testing to get a closer look at what's inside. We see the use of thick aluminium alloy for the housing as promised by SMSL—no complaints here as it makes this feel more premium and solid than some even more expensive DACs that go with plastic. I was also pleasantly surprised to see the various operating voltages listed on the PCB at the test points, which is helpful for those wanting to mod the device as well as for service engineers should there be a fault with the device. Decent components are used throughout, be it on the power delivery section or the various capacitors employed. There is an XMOS XU316 32-bit bridge/encoder usually seen in far more expensive DACs and the actual DAC is an AKM AK4493SEQ 32-bit stereo digital-to-analog converter that I've seen implemented in well-sounding DACs in the price range the SU-1 operates in. There are a few other chipsets onboard which are unidentifiable, but this is the gist of things anyway.


I dug out the SMSL SH-6 amplifier to pair with the SU-1 DAC for testing, especially seeing as how there is no accompanying SH-1 amplifier. Well, there is/was an SMSL SH-1 but it's an HDMI audio extractor accessory and not a headphones amp. The photos above help put the size, or lack thereof, of the SU-1 DAC in context given the SH-6 itself is on the smaller side of average for desktop audio sources. The two were connected using single-ended RCA interconnects. Using the USB input of the SU-1 DAC allows for both data and power together, thus meaning you need only one cable to get the DAC up and running. Turning on the DAC is simple thanks to the button on the front. You also press it to go through the three input options with the respective LED lighting up—the MQA LED is automatic during supported playback. It consumes <5 W on power when running given the USB connection is on USB 2.0 and is rated for a max of 1 A on the 5 VDC channel. In practice I noticed it taking up 2-2.5 W max, this is not a power hungry device.


This is basically a plug-and-play device thus and we don't get an onboard screen as on the SU-6 DAC to show the current playback rate and connection, among other things. Using the SMSL SU-1 DAC with Windows 10 or 11 doesn't require any additional drivers, with Windows recognizing the device automatically. We see that the default firmware provides PCM playback options up to 32-bit, 384 kHz. The XMOS XU316 USB encoder microcontroller comes in handy here, and all your favorite players will recognize the device in WASAPI (Windows Audio Session API) mode accordingly. There should be equivalent drivers pre-configured in newer macOS builds too, but I am not familiar enough to speak on this front.



If you have a device that doesn't accept UAC 2.0, or simply want to try other options, then the generic XMOS USB audio device drivers will be of interest to you. You can find the installer on this page and the latest version at the time of testing was v5.58.0 from earlier this year. Installation is trivial and these drivers create a new output device in Windows while also providing access to the XMOS USB DAC Driver Control Panel. SMSL did not bother to re-skin these drivers with a new name or device ID, as with the likes of FiiO and TOPPING, thus we only get the generic "SMSL USB Audio" device identifier here. Not that it really matters, given you only use it in newer Windows builds if you want to have the stack as an ASIO (Audio Stream Input/Output) device. Set the format to your choosing and choose the buffer size based on latency requirements. Then go to your media player of choice, as demonstrated above with Roon again wherein you can now implement further tweaks that are player dependent. These drivers also provide 24-bit playback support as seen above.