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SMSL SH-9 Review – Modernisation & Moderation

The Pitch –

The SH-9 is SMSL’s midrange headphone amplifier featuring THX AAA-888 technology and is marketed as a direct upgrade to the SH-8 that launched 2 years ago. It retails for $289.99 USD at the time of writing.

Pros –

Modern design and UI, Digital volume control with zero channel-imbalance, Balanced and detailed sound, Well-rounded soundstage, Sub 1-ohm OI

Cons –

Some hiss on very sensitive IEMs, Delay on changing volume and gain, Could do with a little more body and dynamics

Verdict –

Pairing the SH-9 with SMSL’s matching DAC, the user is treated to a delightfully modern and natural sounding stack that doesn’t disappoint.

Introduction –

Where most industries seem to be moving towards integration and convenience, the audio world almost seems to celebrate the analogue, purpose-built legacy long left behind. SMSL’s SH-9 serves as a refreshing change; a modernisation of the headphone amplifier with trick colour-screen GUI and the latest THX AAA module inside. Following the SU-9 balanced DAC, the new SH-9 plays AMP duty to their previous release like the 8-series before it. The SH-9 implements the same modern design with high-res colour screen and handy rotary encoder. It implements 2 mono-amplification blocks to provide balanced output – though take note that the output power and noise characteristics are the same between single-ended and balanced outputs so this is mostly useful to optimise connectivity and prevent ground loops. Similar to the SP200 before it, the SH-9 uses THX’s lauded AAA-888 amp stage and it appears as if SMSL have learnt a thing or two since as the noise figures are noticeably lower on their newest amplifier despite power figures remaining the same.

You can read more about the SMSL SH-9 and treat yourself to a unit on Apos Audio. Be sure to peruse their Ensemble range for discounts when purchasing the SMSL 9-series stack.

Disclaimer –

I would like to the team at Apos Audio for their quick communication and for providing me with the SH-9 for the purpose of review. Apos is a sponsor of THL and affiliate links may be used in this review. However, I personally receive no monetary kickback or incentive for sales or a positive review, all words are my own. Despite receiving the AMP free of cost, I will attempt to be as objective as possible in my evaluation.

Contents –

Specifications –

  • Frequency Response: 0.1 Hz – 500,000 Hz
  • SNR: >137 dB
  • THD: < 0.00006%
  • Balanced IO
  • 256-level relay volume control
  • Switchable gain with pop-less design
  • Output Power: 6W x 2 (16Ω), 3W x 2 (32Ω), 440mW x 2 (300Ω), 220mW x 2 (600Ω)
  • Dimensions: 187.5 x 154 x 40mm

Behind the Design –


If you’re anything Like me, you were probably introduced to THX by the infamous deep note that resounded at the beginning of countless films in the 80’s and 90’s. THX are an audio and video certification company but also develop their own technologies according to their stringent standards. Their AAA (achromatic audio amplifier) technology has perhaps been most lauded, consisting of patented feed-forward error correction topology, super low noise and high efficiency. In practice, we’ve seen a wealth of new Amp designs featuring THX AAA tech at their core boast excellent measurable performance in addition to huge power output. Though tough competitors have come to challenge the throne, THX’s AAA amps are surely nothing to scoff at. You can read THX’s technical breakdown here.

Unboxing –

The unboxing experience is much like the SU-9 with a clean card sleeve containing specifications and model designation that slides off a hard card box. The amp lies within nestled inside a protective foam inlet. Beside is a power cable that can be changed for your region in addition to the remote control. No other accessories are included such as a 1/4″ to 3.5mm adaptor though I’m sure most users are already in possession. It’s a simple yet effective unboxing and enough to get the user started.

Design –

Coming from my brutish THX 789, the SH-9 was a breath of fresh air. This is a sleek metal-clad design modernised by a front-facing colour screen and a high-tech complement to SMSL’s matching DAC. Indeed, those familiar with the SU-9 DAC will find a very familiar experience here with identical dimensions and UI, both also featuring right-hand rotary encoders. And this is a key part of the SH-9’s design, featuring digital volume control. You do miss the weight and smoothness of a standard analogue pot but there’s also no noise or channel imbalance throughout the volume range.

The unit has good heft and sturdiness, and benefits from a clean and even black finish alongside nicely rounded edges for a premium feel. Of note, colour matching between the SH-9 and SU-9 units I have on hand is perfect which is good to see as this isn’t always the case with these products that can vary between batches. Similar to the SU-9 there are only 3 silicone feet on the base which makes it a little less stable when stacked. I have a space limited desk and place my B&W MM-1 speakers on top of my audio stack where rocking can become irksome. Still, an additional foot is easily added, albeit a strange niggle to me.

The IO experience also accompanies that of the SU-9 with two 3-pin XLR inputs on the rear to take advantage of its balanced design alongside RCA single-ended. Do note that there are no preamp outputs, however, the SU-9 does have RCA outputs for those who purchase the entire stack. Besides this, there’s only a 3-pin power input as the SH-9 does have an internal power supply. This is a plus for those requiring larger cable lengths for their setup as this cable is easily swapped out. At the front, the experience is fairly standard, with XLR balanced output, ¼” single-ended output, colour screen and rotary encoder that handles volume and UI navigation. It’s a streamlined and refined package that looks decades newer than the 8-series before it and most competitors in its price range for that matter.

Usability –

As expected, the SH-9 is a breeze to setup and operate, simply plug in the power, inputs and enjoy. While the GUI does bring greater flexibility over a standard button-based interface, I also didn’t find it hamper quick operation of its basic functions; the controls and menu layout is well-considered in my experience. Besides this, the SH-9 provides a refined experience as you would expect from any high-quality source device. There are no noises or pops when plugging/unplugging headphones nor when powering the device on or off. Similarly, the adoption of digital volume control means there are no noises introduced when changing volume nor is there channel imbalance at low volumes. I did note that the unit got quite warm over hours of use, especially with SU-9 on top, but never hot or uncomfortable to touch. Still, it may be better to place the AMP on top which will give it more surface area to dissipate heat.   


With the SH-9 and SU-9 both lined up on my desk, I was able to enjoy the fluidity between usability the company had created. The control scheme is essentially identical to its DAC counterpart with rotary encoder that enables the user to adjust volume with a push granting access to the menu system. This means the SH-9 is able to achieve a clean and button free aesthetic with gain, input, vol mode, screen brightness and software information accessible by the onscreen menu. However, this also introduces additional steps, say, when moving from a headphone to IEM and adjusting gain accordingly, the user has to navigate through the menu rather than simply pressing a physical button as on most amps. The volume control is also less sensitive than a physical pot so it can take some time to adjust between different gear but there are 256-steps of fine control making it easier to set and forget. Besides this, the SH-9 is a simple and fluid device to operate and using the remote can speed up interacting with the device. One upside to purchasing the full SMSL stack is that one remote can be mapped to operate both the DAC and AMP. As before, the screen is bright and sharp and the UI is quick and without issues such as freezing or lag. I also didn’t notice any coil whine on this unit as I did on the SU-9 and didn’t find a negative gain setting necessary as the digital volume system offers a bit more fine control at the lowest volumes for sensitive IEMs than pot designs. Overall, a good user experience.

Next Page: Sound Breakdown

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