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SMSL SU-9 Review – Epiphany

Pros –

Linear sound with dead neutral tone, Coherent and layered presentation, Outstanding resolution, Intuitive UI with remote, Effective sound colour modes, High-quality BT implementation

Cons –

Only 3 rubber feet can wobble when stacked, Prominent coil whine, No single-ended outputs, Smoother top-end won’t suit all

Verdict –

The SU-9 is for those wanting a balanced DAC with a pure sound, excellent staging and strong resolving power without spending a small fortune to get it.

Introduction –

Though almost as diverse as the in-ear and headphone market, buying a source has been heavily simplified by many online resources – buy the JDS Atom and Khadas Tone Board if you’re on a budget, the THX789 and SMSL SU-8 if you value balanced output (albeit at a higher cost). We’ve certainly reached a point where sources are less imperative simply due to the majority now measuring better than the capabilities of human hearing. Is that to say that all sources sound the same or that high-end audio no longer has a place? The answer is invariably not so simple. So, welcome the SMSL SU-9, an update to the SU-8 that features two of ESS’ flagship 9038PRO DAC chips built atop completely redesigned and upgraded circuitry. It promises further improved performance while introducing a higher-res colour screen and Bluetooth in addition to a new external design.

The SU-9 is available for $439.99 USD. You can read more about it and purchase one for yourself from Apos Audio.

Disclaimer –

I would like to the team at Apos Audio for their quick communication and for providing me with the SU-9 for the purpose of review. The company is a sponsor of THL, however, all words are my own and no monetary incentive has been provided at any time for a positive review. Despite receiving the DAC free of cost, I will attempt to be as objective as possible in my evaluation.

Specifications –

  • MQA decoding
  • Remote control
  • THD+N: 0.000095%
  • SINAD: 120dB
  • Linearity: Perfect accuracy to -120dB/20 bits
  • Inputs: USB, Optical, Coax, Bluetooth
  • Outputs: XLR, RCA

The Pitch –

ESS 9038Pro

Though the SU-9 may appear identical to the SU-8 at a glance, it’s important to note the distinction between tiers of 9038. This is the current flagship chip line of ESS but not all are made equally; think of this like a car platform, with cheaper, more efficient incarnations being stripped down but operating from the same chassis. The PRO variant is more expensive than the Q2M and draws more power in return for better performance. It is an 8-channel converter as opposed to the Q2M that only offers 2-channels, enabling it to use 4:1 summing to achieve a 6 dB SNR improvement – about double the performance in this regard since the dB scale is logarithmic.

Balanced Design

There are undisputed benefits to a balanced desktop audio setup. Much of this comes down to the elimination of ground loops and noise rejection, some implementations may also offer lower stereo crosstalk. By eliminating ground loops, balanced audio does not necessarily increase audio quality, but ensures a best-case scenario for performance. It can also offer double voltage swing helpful for high-impedance gear. Often this comes at the cost of doubling the output impedance and cost of production as you essentially need to double the componentry. There has been much discussion on the net so I won’t ramble as this is not a field I am not qualified to dissert nor is it the intention of this review.

Unboxing –

The SU-9 has a straight-forward unboxing similar to SMSL’s other products. Inside the outer sleeve is a card box with the DAC within. It is well-protected within a foam inlet with a plastic sheet that prevents scratches. Beside it is the 3-pin power cable and remote alongside papers. Of note, the power cable is very short, only about 1m long which may limit placement or require the purchase of a longer cable for some setups. Though it would have been nice to see some cables included as well considering the more premium price-point, I do acknowledge that many audiophiles prefer to select each component themselves – so a lower price point in exchange for fewer accessories here is acceptable.

Design –

The SU-9 assumes a svelte form factor that’s a departure from its predecessor. Though it is no work of art like some high-end sources, the 3-piece housing feels well-constructed, being all aluminium and featuring even seems and flush joins. The edges are chamfered and soft on the skin while the anodized finish is even and consistent. The base feels a little hollow when tapped and this isn’t aided by tightening the four corner screws, though play or other noises aren’t apparent once placed on a surface. The front face sports a relatively high-resolution TFT LCD colour display alongside a rotary encoder.

The rear houses the main interfaces that have been expanded relative to the SU-8 as well. Users also no longer have to set the input voltage, it automatically accepts 100-240v 50-60Hz through the 3-pin connector. Beside is a short antenna for its new Bluetooth input in addition to Coaxial, USB and optical inputs. A dividing line separates the inputs from the outputs, that being two 3-pin XLR outs for balanced and two RCA for preamp functionality.

The SU-9 also features an internal power supply that gives the device a nice heft in the hand and stability on the table in addition to omitting the need for an external power brick. This also means the cable can be extended to suit any setup as it uses a common connector. Besides this, setup is as with other sources, simply connect input(s) and desired outputs and enjoy listening. Of note, the SU-9 does not have any single-ended outputs, but you’ll be able to use an adaptor cable and retain the option of going balanced down the road.

Usability –


I am a fan of the device navigation; the integrated screen is clear and bright enough to be visible in well-lit rooms. It provides feedback for options, source and volume with the latter two being displayed constantly on the home screen. This aids an intuitive and simple user experience. All features are accessible by both the rotary encoder on the front and the included remote so users shouldn’t be constrained to using the remote if their setup is within arm’s reach. The remote has 3 channels as well, enabling the user to control their entire stack from just one remote should they be using one of SMSL’s amplifiers too.

Within the menu, users have the option to adjust audio settings in addition to a few liveability tweaks. There’re the usual PCM and DSD filters in addition to DPLL bandwidth that alters jitter attenuation. This isn’t the most accessible option but, in a nutshell, jitter is distortion of the actual waveform during digital to analogue conversion, so it is different to simple latency. Lowering jitter is desirable, measurements have suggested that there is no jitter over USB, but it does help with TOSLINK where the lowest setting works best. The user is able to adjust timing here to some extent here to what sounds best to their ears, I kept this at the stock value since I listen over USB.

The remaining options enable the DAC to control volume on the pre-outs (or set a fixed volume) and adjust screen brightness. A reset button is available if things go wrong and a screen that displays the HW, SW and USB versions provides feedback for firmware updates. Though not common, a toggle to enable and disable the pre-outs would have been appreciated as I split output to active speakers and a sub, it would be convenient to be able to turn both off from one device when listening to headphones. Nevertheless, the overall usability experience here is very straight forward and streamlined making it suitable for seasoned audiophiles and newcomers alike.


Bluetooth is a new and welcome addition, signified by the screw-on antenna. It works without the antenna too and the antenna can be angled horizontally if below another device in a stack. Of course, the range is compromised in so doing. Selecting Bluetooth through the source selector enables pairing and it auto connects to previously paired devices, nice and simple. Range was very good. With the external antenna attached, I was able to cross 3 rooms with double brick walls and the sound didn’t become intermittent. Latency was also on the low side with barely noticeable lip sync that wouldn’t irk during videos or movies. This makes it suitable for TV setups and larger rooms. It supports LDAC and the display provides feedback on the sample rate. I was able to stream at up to 96kHz from my Pixel 4 without issue. 

Next Page: Sound, Pairings & Verdict



Ryan Soo

Ryan Soo

Avid writer, passionate photographer and sleep-deprived medical student, Ryan has an ongoing desire to bring quality products to the regular reader.


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