SMSL SU-9 Ultra Review

SMSL SU-9 review featured

In today’s article, I’m reviewing the SMSL SU-9 Ultra DAC. The SU-9 Ultra is a revised version of SMSL’s popular model. It remains largely unchanged from the SU-9 Pro but comes equipped with an AK4191 + AK4499EX combo. It’s priced at $499.

Disclaimer: This sample was provided by Shenzhen Audio for an honest review. All observations and opinions here are my own, based on my experience with the product.

SMSL SU-9 Ultra Review
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Highly-resolving sound
Natural, organic tonality
Black background with precise imaging
Bright, clear colour display
Compact size
Less digital inputs compared to DO300
Our Score

SMSL SU-9 Ultra

In the Box
  • SU9 ULTRA * 1
  • Remote Control * 1
  • Charging Cable * 1
  • User Manual * 1
  • Brand Card * 1


I almost decided to leave this part of the review out because most mid-tier DACs offer the same features these days. But then I remembered that people reading this might be new to the hobby or simply aren’t aware. Anyway, why am I saying all this? Let’s get on with it!

First of all, if MQA is at all important to you then SMSL has got you covered. The SU-9 Ultra supports MQA full decoding and MQA-CD. The device can be used with a fixed-level output or as a preamp and comes with the usual array of AKM digital filters which can be accessed via the system menu.

SMSL SU-9 settings menu

The AK4191 + AK4499EX combo makes an appearance here, in place of the ESS DAC chip used in the SU-9 Pro. Also in attendance is an XMOS XU316. You can plug and play the SU-9 Ultra on both Windows and Linux without needing to install any drivers. However, installing the driver will add ASIO support on Windows devices. SU-9 Ultra supports up to the now almost ubiquitous standards of PCM 32bit/768kHz and DSD512.

Bluetooth 5.0 is here too. I’m not sure why it isn’t 5.3 (maybe to keep costs down) but regardless, our favourite wireless audio codecs are supported, including SBC, AAC, aptX, aptX HD and LDAC.

SMSL SU-9 Ultra front panel


Regarding physical design, the SU-9 Ultra chassis is about as utilitarian as you can get. It’s essentially a black box with rounded edges. Fortunately, once you power on the device there is a nice colour display on the front to give it some personality.

Apart from the display, the only other feature on the front panel is the volume knob. This knob is also a button used to turn the unit on and off, as well as cycle through inputs and navigate the system menu. The menu is the same one found on many other SMSL DACs, such as the DO200 MKII, DO300 and DO300EX etc.

Digital input options include optical, USB-C and coaxial. Balanced XLR and single-ended RCA are the analogue output choices. Output power is 5Vrms for XLR and 2.5Vrms for the RCA outputs.

SMSL SU-9 Ultra rear I/O panel


When I tried out this unit, I stumbled upon something unexpected. I’ve checked out quite a few SMSL products before, so I had a pretty clear idea of what to expect in terms of performance. But the SU-9 Ultra totally changed the game. Right from my first listen, it caught me off guard — it’s in a league of its own compared to other SMSL units I’ve tested, even surpassing the excellent DO300EX, which also uses the AK4191 + AK4499EX combo.

At first, I thought it might be a synergy between the SU-9 Ultra and the Topping L70 that I had connected it to. But that didn’t make sense because I’ve used the L70 with other SMSL models in the past.

At the time, I was using the Moondrop Para headphones and had been testing those already for a couple of weeks. With the SU-9 Ultra added upstream, the Para suddenly came alive, as if they had just leveled up. Instrument separation improved. The soundstage sounded more organized and the overall resolution had become clearer.

SMSL SU-9 display

The spacing between instruments and vocals is not just spacious; it’s a void painted in obsidian, offering a blackness that lets each note emerge with crystalline precision. This DAC is the maestro of silence, where the absence of sound becomes as defining as the notes themselves.

While some might belt out a cacophony of exaggerated bravado, the SU-9 Ultra exudes quiet confidence. It doesn’t need to shout to be heard; its robustness lies in its calm demeanour, delivering sound with the serenity of a Zen master. The confidence it exudes is palpable, like a seasoned pianist striking each key with assured grace.

And let’s not overlook the analog-like allure this DAC possesses. Instrument notes dance forth with the charm of a vinyl record, marrying well-defined clarity with an organic warmth that makes you question the digital nature of the beast. It’s the paradoxical fusion of precise articulation and analog soul.

Rear I/O angled view



The main external differences on the DO300 are the extra I2S and AES inputs. Internally, the DO300 features an ES9039MSPro DAC chip, while the SU-9 Ultra adopts the latest AKM flagship.

Both of these DACs sound great but to my ears, the SU-9 Ultra comes out ahead in this comparison. DO300’s staging is not as well-defined—the background is blacker on SU-9 Ultra and there is more spacing between instruments.

SU-9 Ultra’s lows are tighter and have improved layering but carry just as much impact. Midrange and treble notes have greater density and while this doesn’t create the most expansive stage, it contributes to improved instrument separation and spacial imaging.

If you need either I2S or AES input the DO300 is still a fantastic DAC that offers great performance for the money. Otherwise, I would consider the SU-9 Ultra to be a better performer in terms of pure audio quality.

Angled view of the SU-9 Ultra


Despite its unassuming exterior, the SMSL SU-9 Ultra DAC has me hooked on its performance. After hearing it, I can hardly believe the SU-9 or SU-9 Pro never made it onto my desk.

SU-9 Ultra effortlessly translates digital signals into an audio experience that belies its price point. Its simplistic design conceals a treasure trove of sonic clarity and value, making it a good choice for audiophiles seeking exceptional sound without breaking the bank.

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