Review: SMSL SU-9 DAC – Cleanliness Is Next to Godliness

The SMSL SU-9 DAC.
The SMSL SU-9 DAC.

A midrange-priced DAC sporting essentially every possible option.

Thank you to HiFiGo for providing the SMSL SU-9 DAC for review purposes. If you’d like to purchase the SU-9, it is available from HiFiGo.

The SMSL SU-9 is an ESS Sabre chip-based desktop DAC with a middle-of-the-road price tag. It features balanced outputs, the latest and greatest Bluetooth codecs, support for 32bit/768kHz files, DSD512, and full native MQA decoding. If you like to peruse technical specifications, you’ll soon notice that the SU-9 boasts just about every top-of-the-line option.

Priced well under $500, it may also be the most affordable DAC that’s chock-a-block full of all these premium features. SMSL is one of a few Chinese companies delivering feature-rich products at almost unbeatable price to performance ratios. It’s exciting to see how these companies are pushing and advancing the personal audio industry.

The SU-9 is a full MQA decoder.
Bottom Line

There’s no question that the SU-9 more than fulfills the DAC needs for a great number of systems and audiophiles. If you are in the market for an ESS-based DAC, and your budget allows, there are very few reasons you should be considering anything else than the SU-9.

What We Like
  • Support for all high-resolution music formats
  • Native MQA decoding and rendering
  • Remarkably full-featured menus system allows for virtually unlimited tweaking
  • Transparent but smooth sound
  • Support for all Bluetooth formats including UAT
  • Balanced XLR and single-ended RCA outputs
  • The internal power supply does not require wall-wart
  • Clear and bright screen
  • Included remote
What We Don't Like
  • The menu system may be overwhelming for those looking for a more streamlined experience
  • Three rubber feet are not as stable as four
  • Display always shows ‘99’ in fixed-output mode
  • Remote control shared is between devices and not intuitively labeled

The SU-9 is an upgrade to the SU-8, and while it maintains the previous model’s footprint, the SU-9 significantly updates its functionality. The SU-9 adopts SMSL’s current black aluminum case design with a front LCD screen and an aluminum knob. The (mobile version) ES9038Q2M DAC chip from the SU-8 is replaced by the ES9038Pro chipset, with Bluetooth and MQA support added to the SU-9 as well.

The SU-9 is a full MQA decoder.
The SU-9 is a full MQA decoder.
The Pro chipset is an 8-channel digital to analog converter and offers a 6dB SNR improvement over the ES9038Q2M.

As you may imagine from the combo of SMSL’s pedigree and a TOTL ESS chipset, the SU-9 is designed to dominate the measurement-based DAC category. Its technical prowess is undeniable. The feature set is incredibly robust. Adding to the SU-9’s resume is an interface full of user-selectable sound and filter modes. In short, the SU-9 is a music-loving tweaker’s dream!

I guess we’d better give it a listen to see if it delivers on all that promise.

Company Overview

SMSL stands for the Foshan ShuangMuSanLin Technology Co., Ltd. Founded in 2009, SMSL is located in Shenzhen, China. They have their own R & D, manufacturing, and marketing teams and specialize in producing audio products, including DACs, stereo headphone amplifiers, speakers, and power amplifiers.

SMSL has established a comprehensive sales network, and its products are exported to more than 30 countries worldwide. SMSL states that they are “quality-based, technology-guidance, customer central.” They strictly execute the Electronics Industry rules (EICC) and have passed the CCC, BQB, MFi, CE, FCC, RoHS, CE-EMC, CE-LVD, WEEE certifications.

Technical Specifications

  • Form: DAC
  • Digital inputs: USB/Optical/Coaxial/Bluetooth
  • Analog outputs: RCA/XLR
  • THD+N: 0.00009%(-121dB)
  • Dynamic range: XLR 130dB, RCA 123dB
  • SNR:130dB
  • Output impedance: XLR 207Ohms, RCA 142Ohms
  • Bit depth: USB 1bit,16-32bit, Optical/Coaxial 1bit,16-24bit
  • USB sampling rate: USB PCM 44.1-768kHz, DSD 2.8224-22.5792MHZ,
  • Optical/Coaxial sampling rate: PCM 44.1-192kHZ, DSD dsd64(DoP)
  • Bluetooth sampling rate: UAT: 24bit/192kHz (1200kbps/900kbps/600kbps), LDAC: 24bit/96kHz (990kbps/660kbps/330kbps), aptX-HD: 24bit/48 kHz-576kbps, aptX: 16bit/44.1 kHz-352kbps, SBC: 16bit/44.1 kHz-328kbps, AAC: 16bit/44.1 kHz-320kbps
  • Power Consumption: 5W, <0.5W (standby)
  • Size: 187.5X154X40mm (WxHxD)
  • Weight: 800grams
The box displays surprisingly few technical specifications.
The box displays surprisingly few technical specifications.

Packaging

SMSL doesn’t waste any time trying to sell you with the box. For such a feature-rich and complex device, the outer black cardboard sleeve is surprisingly devoid of technical data or specifications. Instead, it’s a clean design with the brand and model prominently displayed and a host of logos (MQA, ESS, Hi-Res Audio, etc.) along the top and bottom.

Inside is a plain white box with a foam insert protecting the device. Accessories are pretty minimal as well, with only the bare necessities included in the package.

Inside the box.
Inside the box.

In the box

  • SMSL SU-9 DAC
  • Power cord (1m – grounded 3-pin)
  • Remote control (same design shared between models)
  • Bluetooth antenna
  • USB-A to USB-B cable
  • Manual
(2-AAA) batteries for the remote are not included, and there are no analog (RCA or XLR) cables in the box.
The included accessories are fairly minimal.
The included accessories are fairly minimal.

Design

The SU-9 features SMSL’s most recent design and form factor. It’s constructed of a single piece of CNC milled aluminum for the front, back, and sides, with separate top and bottom plates screwed on. It’s well made and feels robust and clean. The front panel is only interrupted by a bright 1.9” full-color TFT LCD color screen and a single multi-function knob.

The screen shows the format of the digital file being decoded on the left, and the volume on the right.
The screen shows the format of the digital file being decoded on the left, and the volume on the right.
One minor complaint is that the volume level always occupies the right half of the screen. In this fixed-output mode, the majority of the screen real estate will prominently display (an unchanging) ‘99’. I would prefer a small ‘fixed output’ indicator and all that screen space repurposed.

The aluminum knob is a push-to-select rotary controller which allows the user to power the device on and off, control the volume, and enter and select from the menu options. The knob is also a perfect match for the SMSL SP200 amplifier, has a notched feel when turned, and works well.

On the bottom of the SU-9 is a multi-pin port with an unknown purpose. Does it simplify in-factory re-programming? Will it add support for device connections (like an amplifier or streamer) in the future without external cables? It’s very mysterious!

The three rubber feet and mysterious port on the bottom of the SU-9.
The three rubber feet and mysterious port on the bottom of the SU-9.
One SMSL design oddity is to only use three rubber feet on the bottom of their devices. I don’t get it. Yes, heavy cords will drag the SU-9 over into a crooked lean.

The rear panel is fully kitted out with a 3-pin IEC power socket (for the internal power supply), digital inputs (USB, optical, and coaxial), analog outputs (RCA and XLR), and a Bluetooth antenna. The analog outputs are concurrently active and can be toggled in the menu between fixed line-level or volume-controlled for use as a pre-amplifier.

The back of the SU-9 is rich with connection options.
The back of the SU-9 is rich with connection options.

Interface

The combination of a clear, bright screen and a tactile knob makes for a good user experience. Long press to power toggle the SU-9, short press to enter the menu system, and rotate for volume control and navigation. It’s intuitive. My only trivial concern is that the main menu does not have an ‘exit’ option to go back to the main screen, and it is necessary to wait 10-15 (long) seconds for it to time out.

The remote is simple and functional as well, although because it is a shared remote between SMSL devices and can control three components, you must press the ‘C’ button before it functions with the SU-9. As one who eschews reading the manual upon the initial setup, I was quite convinced that the remote was DOA after swapping a few pairs of batteries. Once I stumbled across the ‘C’ button necessity, all was well.

The plethora of options found within the sub-menus led me to a bit of self-discovery. Some folks don’t want to be shackled by the manufacturer’s decisions and compromises. They want to change and tweak every function, reveling in the control and the minutiae. The SU-9 is the perfect DAC for this consumer.

Other folks (and it turns out that I’m one of them), prefer a DAC to automatically be set to the “BEST SOUND” option and don’t want to spend their valuable listening time figuring out which of the last eight options sounded better than the current one. A power button, input selector, and volume control may be enough.

Lest you think I’m exaggerating the sheer number of menu options, the SU-9 allows users to toggle between seven PCM filters, four DSD filter cutoffs, ten sound colors, fifteen DPLL bandwidth settings, and the list goes on. Multiply that all together to see how many unique combinations you can come up with.

The SU-9 sneers with contempt at the KISS (keep it simple stupid) philosophy.

The measured differences between the user-selectable filters in the SU-9. (From: audiosciencereview.com)
The measured differences between the user-selectable filters in the SU-9. (From: audiosciencereview.com)
  • INPUT – Change between USB, Optical, Coaxial, and Bluetooth digital inputs.
  • PCM FILTER – These are the standard filters for current ESS DAC chipsets. In my experience, they make minimal sound changes. You can play around with them, but I tend to leave it at the default apodizing fast roll-off filter or brick wall filter.
    • Linear phase fast roll-off filter
    • Linear phase slow roll-off filter
    • Minimum phase fast roll-off filter
    • Minimum phase slow roll-off filter
    • Apodizing fast roll-off filter
    • Hybrid fast roll-off filter
    • Brick wall filter
  • DSD FILTER – 47, 50, 60, or 70 kHz – Alters the cut-off frequency of the DSD stream. I stick with the default.
  • SOUND COLOR – Changes distortion levels to tailor the sound. A more noticeable impact on the timbre and overall sound than the PCM Filter options, but is subtler than most EQ presets. Levels 1-3 affect the intensity of the effect. Rich and Tube tend towards warmth while Crystal is brighter.
    • Standard
    • Rich 1,2,3,
    • Tube 1,2,3
    • Crystal 1,2,3
  • PRE MODE – Set to ‘Vol Fixed’ if using as a DAC for an amplifier, or ‘Vol Variable’ if wanting volume-controlled preamplifier functionality.
  • DPLL – 1, 2, 3, 4, 5, 6, 7 (default), 8, 9, 10, 11, 12, 13, 14, 15 – bandwidth adjustment that affects jitter attenuation, and is most likely only useful if using the optical input.
  • BRIGHTNESS – 1, 2, 3, 4, 5, 6 – Changes the screen brightness (1 lowest, 6 highest).
  • RESET – Resets the unit back to default values.
  • VERSION – Displays the current software, hardware, and USB versions.
MQA playback disables PCM and DSD filter settings.

Internals

As I’m sure you’ve picked up, the SU-9 is a technological marvel. It boasts the flagship, 8-channel, ES9038Pro chip, and associated ES9311 voltage regulators. The output stage is based on Texas Instruments Burr-Brown OPA1612 dual op-amps (one for single-ended RCA and two for balanced XLR).

The SU-9's internal circuitry.
The SU-9’s internal circuitry.

All that processing power means the SU-9 natively and fully decodes MQA, supports 32-bit/768kHz PCM, and DSD512.

Like the SMSL SP200 amplifier, the internal ultra-low noise power supply is located within the case, rather than utilizing a wall-wart type power adapter.

The SU-9's power supply.
The SU-9’s power supply.

Bluetooth

The SU-9 supports all the standard Bluetooth codecs, including AAC, SBC, aptX, aptX-HD, and LDAC. Of note, it also supports the new Ultra Audio Transmission (UAT) codec designed by the HiBy company. UAT uses HiBy’s proprietary algorithms to work around data transfer limitations to support higher resolution audio. Initially only available on HiBy DAP products, UAT appears on other devices like the Hidizs AP80 Pro and Cayin N8.

Any improvement to Bluetooth fidelity is welcome, so it’s great to see UAT included in the SU-9.

Bluetooth CodecBit Depth (bit) / Sample Rate (kHz)Supported Bit Rate (kbps)
UAT24/1921200/900/600
LDAC24/96990/660/330
aptX-HD24/48576
aptX16/44.1352
SBC16/44.1328
AAC16/44.1320

With the external antenna attached, the Bluetooth range is impressive and more than capable of uninterrupted playback from my phone, even at the extremes of my smallish house. Using the UAT connection from my Hidizs AP80 Pro, audio quality is excellent and virtually indistinguishable from a wired connection. Bluetooth audio has come such a long way in the last few years.
Closeup of the XMOS USB chipset.
Closeup of the XMOS USB chipset.

SMSL SU-9 Sound

As the SU-9 has a plethora of sound-shaping options, the notes below reflect listening with the default settings to remain consistent. I paired the SU-9 with several amplifiers, including the SMSL SP200 (THX amplifier), Bottlehead Crack (OTL tube amplifier), and Hagerman Tuba (single-ended, zero-feedback, parafeed EL84 triode amplifier). Headphones varied primarily between the Sennheiser HD650, Audeze LCD-2, HEDDphone, and Ultrasone Edition 15 Veritas (amongst a few others).

The SU-9 pairs nicely with the SP200 amplifier.
The SU-9 pairs nicely with the SP200 amplifier.

Frankly, amplifier and headphone choice have a more significant impact on the sound signature than does the DAC. There. I said it, and I stand by it. In my world, high-quality DACs should perfectly deliver the music with a minimum of coloration and imparted personality. They should provide a flawless foundation that the listener can build their own sound signature preferences upon.

That isn’t to say that DACs should sound sterile, lifeless, or dull. And those are criticisms sometimes directed at ESS Sabre chipset-based DACs. One way that the SU-9 avoids this trap is to provide so many ways to tailor the sound. Want it to sound different with your gear? Head on in to the menus and start changing things.

The ES9038Pro chipset.
The ES9038Pro chipset.

But as they say, a DAC is more than simply a chip, and the entire circuit design and componentry all play a role in the overall sound. In this case, the SU-9 leans a hair more towards the full, warm, midrange-focused side of things, at least as far as ESS DACs go. It’s still remarkably detailed and resolving, and manages to avoid undue glare and grain.

Indeed, the choice of attached amplifier dramatically determines what the end product sounds like. Paired with an ultra-clean THX amplifier like the SP200, the sound is far more analytical and transparent than with tubes in the chain. The technically capable SU-9 makes an excellent base for almost any system and is flexible enough to fulfill most conceivable tastes.

Hooking up a DAC to an amp can create a wild jungle of cables.
Hooking up a DAC to an amp can create a wild jungle of cables.

The measurement-minded folks over at AudioScienceReview.com had many positive things to say regarding the SU-9. Several Chinese designed and manufactured DAC companies (such as Topping, Soncoz, Khadas, and SMSL) seem to be in a perpetual arms race for measurement perfection, and the SU-9 is the latest contender.

“Wow! Another DAC nearly maxing out the distortion+noise meter in my analyzer! The SINAD of 120 dB puts the SU-9 way up there in rankings… Our old friend the “ESS IMD Hump” is still there but 90% suppressed… Linearity which is a measure of accuracy is perfect… Jitter over USB is non-existent.

…a trend to achieve perfection in desktop DACs and the SMSL SU-9 is yet another example of that. We have another great “instrument grade” DAC on our hands providing absolute transparency to the source beyond any threshold of human hearing.” – AudioScienceReview

The SU-9 sounds linear, virtually uncolored, and transparent. It’s not so analytical as that it overshadows the music. Instruments and vocals remain natural and real sounding. The SU-9 is just smooth enough to balance all the details.

Is it hugely different from listening to the great Soncoz LA-QXD1 DAC or another top-tier measuring 9038-based DAC? Of course not. The SU-9 simply shares too much of the same pedigree to be anything but reasonably similar.

The SU-9 (bottom) compared to the Soncoz LA-QXD1 DAC (top).
The SU-9 (bottom) compared to the Soncoz LA-QXD1 DAC (top).

The SU-9 does, however, have tons of features and a great screen to differentiate it from comparable (and competing) models. It also has a little audible edge in how it rounds off the sharp corners and presents a smooth, enjoyable sound.

Where to Buy

Conclusion

What makes a DAC futureproof? Include every conceivable input and output option: check. Include Bluetooth support for all codecs, including new up-and-comers: check. Support the highest resolutions and formats: check. Let the user change every conceivable setting: check.

Based on that checklist, the SMSL SU-9 is the very definition of futureproof.

It’s good to be attractively and robustly made and feature some perks like a legible screen and remote control. A reasonable price tag also helps.

Oh yeah, it must sound good as well.

There’s no question that the SU-9 more than fulfills the DAC needs for a great number of systems and audiophiles. If you are in the market for an ESS-based DAC, and your budget allows, there are very few reasons you should be considering anything else than the SU-9.

The SU-9 shows that the Chinese-made, perfect-measuring DAC race is starting to mature. While lower-priced models may share some of the same features, the SU-9 ups the ante with more focus on the sound. The ability to tailor the ‘sound color’ distortion levels and an overall smoother presence distinguish the SU-9 from lesser models.

Frankly, unless you are only interested in esoteric and uber-expensive DAC options, I’m not sure who wouldn’t be happy with the SU-9 anchoring their system.

1 comment

  1. Trav, you hit the nail on the head. The SMSL SU-9 is the DAC for Everyman. It’s priced affordably, it’s packed with features, it’s future proof (well, as much as any DAC can be), it’s MQA full decoding is nigh on perfect, and it’s sounds great. What more can one ask?

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