SMSL SX-8s Stack Review – DAC/AMP On a Diet

Introduction –

SMSL has received no shortage of accolades for their high-quality implementations of high-performance components at a reasonable price. While competitors, Topping especially, share equal headline; I see the two as quite complementary as their products exist in alternating price tiers. I previously reviewed the SX-9 devices that I found to offer an impressive medium-high-end experience, the SU-9 especially. SMSL also share a focus on objective performance and while they may not always top the charts, I found their products to hold up very well in subjective listening. It is for both of these reasons that the affordable SX-8 devices were such a hit and, if the SX-9 devices are out of budget, the new SX-8s devices look to brings a very similar form factor and feature-set at a noticeably lower price.

The SMSL SU-8s DAC and SH-8s Headphone Amplifier retail for $359.99 USD and $229.99 USD respectively. You can read more about them and treat yourself to a set on Apos Audio.

Disclaimer –

I would like to thank John from Apos Audio and the team at SMSL very much for reaching out and for providing me with the SH-8s and SU-8s for the purpose of review. All words are my own and there is no monetary incentive for a positive review. Despite receiving the stack free of charge, I will attempt to be as objective as possible in my evaluation.

Contents –

• Page 1: Unboxing, Design & Usability
• Page 2: SU-8s Sound Breakdown
• Page 3: SH-8s Sound Breakdown
• Page 4: Comparisons & Verdict

Behind the Design –

SU-8s

The SU-8s is built atop ESS’ high-end ES9068AS DAC chip, a 2-channel DAC chip supporting Hyperstream II. USB processing is provided courtesy of a powerful XMOS XU216 controller, both enabling the DAC to decode 32bit/768kHz PCM, DSD512 and MQA. The output section is covered by 5 OPA1612 opamps. SMSL has also implemented Bluetooth 5.0 connectivity with aptX HD support. You can definitely see parallels here to the higher-end SU-9 besides that model’s use of the ES9038 Pro DAC chip.

SH-8s

Unlike the SH-9 which used THX’s AAA-888 platform, the SH-8s is using SMSL’s proprietary PLFC (precision linear feedback circuit) amplifier design which promises ultra-low distortion. They promise an inaudible noise floor of just 1.3µV. At a glance, the amplifier offers a whopping 6W of power into a 16 ohm load, bringing it up to par with modern competitors and matching the higher-end SH-9. In addition, it uses pop-less relays similar to most competing designs, preventing additional noise during use.

Design –

The SX-9 devices surely made an impact; users loved their clean, modern and colour display-centric designs. The SX-8s devices draw many parallels, in fact, the SU-8s DAC is essentially identical to the SU-9 besides the model designation print on the front and rear and slightly smaller dimensions. On the contrary, the SH-8s trades the colour display for a 3 flick switches and the rotary encoder for a good old-fashioned potentiometer. This makes it more of a hybrid between the base SH-9 chassis and the haptics and usability of the original SH-8. Arguably, the user experience and practicality here are superior to the pricier SH-9, albeit, the same cutting-edge aesthetic is compromised if that is a priority for you.

Otherwise, there isn’t much to expand upon here that wasn’t already discussed in my previous SX-9 reviews. The devices have a relatively small footprint and a very clean and modern look, even the SH-8s with its switch-based UI. The units have a good sense of solidity with no hollowness nor loose-fitting panels. I was impressed once again by the finish, with smooth edges and a uniform anodized exterior that both contribute to a premium haptic experience. With aluminium all-around the devices stay put well on a desk and the construction offers good heat dissipation when required. However, as before, both do only include 3 rubber feet on the bottom which means they can rock. This is irksome if you are space limited and want to place small speakers on top, for instance.

The IO experience is also essentially identical to the SX-9 devices, both sport 3-pin XLR connectors for balanced IO in addition to single-ended via RCA. They use IEC connectors and are powered by an internal power supply which opens up more flexible placement as you can get power cables in varying lengths, and also means you don’t need an external brick, a huge pro in my books. The SU-8s has four inputs, USB Type-B, optical, coaxial and Bluetooth like the SU-9. The SH-8s is almost identical to the SH-9 as well, offering 4-pin XLR balanced output and single-ended over ¼”. It receives input over XLR or RCA.

Usability –

The stack is as easy to set up as any others, connect your preferred input to the SU-8s, connect it to the SH-8s via XLR balanced or RCA single-ended and enjoy. I would personally recommend using XLR, I found it to help with the SH-8’s soundstage width in my subjective opinion.

SU-8s

The experience here is almost identical to the SU-9 with the same colour display and rotary encoder-based control scheme, the remote operation is also identical. The screen is clear and bright, even in well-lit rooms. Upon power up, it displays the volume level and input/sampling rate. Pressing the rotary encoder allows the user to adjust all settings, as a result, using the remote is not necessary unless the DAC is placed far away from the user. The menu provides options for inputs, outputs (reverse channel, etc), PCM filter, SPDIF mode, sound colours and pre-mode.

You can also adjust display brightness and set the screen to dim after a certain period of time. The colour modes are interesting, they aren’t eQ presets but use distortion to alter the sound. They are subtle but this makes them especially usable in my opinion, I can easily see some using these to optimise some pairings. DPPL settings are available as well,, which allows the user to alter jitter attenuation. I also didn’t experience any coil whine as on the SU-9 so it is likely this was a result of unit variation rather than an outright fault in the design.

SH-8s

Where I found the digital interface hurt the SH-9’s overall usability experience, the SH-8s provides a back-to-basics approach that was refreshingly tactile and simple. There are three two-way switches on its face alongside a smooth, well-weighted analogue pot. During my testing period, the pot never became scratchy but only time will tell if this will remain the case long term. The switch based operation is very simple. The first controls power, the second input between XLR and RCA and the third toggles low/high gain.

Do note that the SH-8s has no RCA outputs and does not support preamp or pass through, this is purely a headphone amplifier. A blue status LED denotes power and the amp powers on and off very quickly and never produced any pops or noises when doing so. It also barely produced any heat during use, even on high-gain. As such, I would be comfortable tucking it away or placing it at the bottom of a stack should you want to pair this with a smaller DAC. Altogether, perfectly simple and effective experience.

Next Page: SU-8s Sound Breakdown