SMSL DO300EX Review


SMSL DO300EX AKM Review – AK4499EX DAC & Headphone AMP

The ‘EX’ in the name of the new SMSL DO300EX is a reference to the latest EX series DAC chip technology of AKM.

For me, the important thing here is not the EX in the name, but the revised flagship DAC chip called 4499EX at the heart of the DAC’s board. The DO300EX incorporates an AK4499EX DAC chip coupled with an AKM AK4191 digital filter interface. This chip combo and the DO300EX’s symmetrical architecture enable it to decode up to PCM 32bit 768kHz and DSD up to DSD512. They also accept MQA streams and offer a distortion level of less than 0.00006% (-124dB). This chip is AKM’s best chip available at the moment and combined with SMLS’s prowess in DAC development and implementation, the result is a very competitive product, priced at $469 USD.

SMSL DO300EX Review
“EX” comes with a new design and headphone outputs.

SMSL DO300EX features high-power headphone amplification as well. It provides a strong output thrust of up to 2W on a 16Ω impedance load and 1W on a 32Ω impedance load. SMSL has featured 4.4mm balanced and 6.35mm single-ended headphone output modes on the device. With precise volume adjustment, users can use both high-sensitivity and low-sensitivity IEMs and headphones with the DO300EX with ease.

The DO300EX also incorporates the latest technologies and improvements. Let’s take a look at the details. First of all, we see the use of the new USB controller from XMOS. Called XU316, this 32-bit multicore controller replaces the long-running XU216. The plug-and-play feature, which allows the product to work seamlessly with all kinds of devices, has been further improved and offers maximum compatibility and stability with all devices except applications that require Windows-ASIO.

SMSL DO300EX Review 16 e1694800432743

The SMSL DO300EX has LDAC and comes with Qualcomm’s QCC5125, a premium-tier chipset. It supports popular codecs such as LDAC, and AptX HD.


  • Support MQA decoding, support MQA-CD;
  • New 3rd generation XMOS XU-316, PCM support up to 32bit/768kHz, DSD support to DSD512;
  • Flagship DAC chip AK4191+ AK4499EX.
  • Dual mono design, one AK4499EX per channel, distortion as low as 0.00006% (-124dB);
  • Uses 5 high-end dual op amps and a large number of audiophile components;
  • Adopts 2nd PLL to eliminate JITTER during SPDIF transmission;
  • The new self-developed CK-03 clock processing circuit greatly reduces clock jitter;
  • Support DOP independent display function, accurately determine the current decoding format;
  • USB, optical fiber, coaxial, AES, and I2S support DSD transmission, coaxial and optical fiber support DOP64;
  • Use tempered glass to fully fit the color IPS display;
  • Built-in low-noise power processing, while improving power efficiency, and lower power consumption;
  • Combined with multiple low-noise regulated power supplies, it provides a stable, reliable, efficient, and low-noise power supply system.
  • Qualcomm high-end Bluetooth chip, support LDAC (24bit/96kHz), APTX/HD, SBC, AAC;
  • High-quality all-aluminum alloy shell supports high-quality gold-plated input and output connection terminals;
  • Japan Audio Association (JAS) Hi-Res certification;
  • Equipped with full-featured remote control.
SMSL DO300EX Review
DO300EX has upgraded stands.

Technical Specs

  • Model: SMSL DO300EX
  • Input: USB/Optical/Coaxial/Bluetooth/12S
  • Output: RCA/XLR/4.4mm+6.35 Headphone Jack
  • Line Output Amplitude: XLR: 5.2Vrms, RCA: 2.5Vrms
  • Headphone Output Power: 2W x 2 (16Ω), 1W x 2 (32Ω)
  • Headphone Output Gain: Low :0dB, High: +7dB
  • THD+N: 0.00006%(-124dB)(UN-WTD)
  • Output Impedance: XLR: 200Ω, RCA: 100Ω, Headphone outputs : near 0Ω
  • Dynamic Range: XLR: 132dB, HPA: 127dB
  • SNR: XLR: 132dB, HPA: 127dB
  • MQA Decoding: USB, Optical Toslink, Coaxial
  • USB Compatibility: Windows 7/8/8.1/10/11, Mac OSX 10.6 and above, Linux
  • Size: 222x39x207mm(WxHxD)
  • Weight: 1.54kg/3.40lbs
  • Price: $469

I want to thank Aoshida Audio for providing me with the review sample of DO300EX. 

Packaging & Accessories

The DO300EX comes with a remote controller, a BT antenna, a power cable, and a Type-C to Type-C cable along with a couple of manuals.

Design & Build Quality

Although the model name includes the DO300, the EX variant comes with a new design language compared to the vanilla DO300. It features a floating display window design that is accented by a fully bonded, color IPS display screen. This not only adds a layer of sophistication but also provides a dedicated DOP (DSD over PCM) display function. The retro function knob design completes the visual treat, allowing you to navigate effortlessly. A long press of this function/volume knob puts the device on standby and a short press triggers the settings menu on the screen.

SMSL DO300EX Review
Retro style function/volume knob

The front panel also features a 6.35mm single-ended headphone interface and a 4.4mm balanced headphone interface, providing ample thrust for different headphone types, including 16Ω 2000mW x 2 and 32Ω 1000mW x 2.

Measuring 22 x 20.7 x 3.9 centimeters (WxDxH), the DO300EX is not the most compact stack SMSL has ever made, but it is smaller than its competitors, assuming it delivers high-end performance.

The DO300EX offers 5 inputs including USB, Bluetooth, Optical, Coaxial, and I2S (HDMI), allowing you to connect your preferred source effortlessly. It also features 2 headphone outputs (4.4mm, 6.35mm), and 2 Line Outputs (XLR, RCA), and even includes a PRE MODE for added flexibility.

SMSL DO300EX Review
DO300EX comes with USB-C (TYPE-C) input instead of USB-B.

The quality of the sockets used is great, as expected from SMSL. The sockets seem rigid and durable with no wobble. I do not see any chassis imperfections that could’ve occurred during CNC and there are no assembly issues either. SMSL has been quite consistent in this regard for a long time.

Controls & UI

Like many modern DACs, the DO300EX can output a line-level output, and work as a pure Digital-to-Analog-Converter, or feed a power amp with a variable-level output, like a pre-amplifier. Bonus point, you can even use both outputs at the same time, or just one at a time (XLR/RCA), in case you only use one kind of amp with this DAC.

DO300EX’s menu can be accessed with the volume knob or with the remote control that doubles as a joystick. In the standby mode, a single press will power it on and another press will enter its user menu where the following features can be accessed in the settings.


When the SMSL DO300EX was offered to me for review, I was very excited as, after the success of the DO300, I was curious to see what SMSL could do with AKM’s top-of-the-range DAC chip. For those of you who do not know me, I have no clear preference between the ESS and AKM, as the success of the chip is directly related to the implementation and engineering behind the product.

The DO300EX sounds natural, impressively clean, and accurate. It is tonally balanced, with a colorless signature across the spectrum. The DO300EX features the same, mighty impressive technical ability as the DO300. It is not surprising since SMSL has been constantly upping its game throughout 2022-2023. Its resolution is just brilliant.

I believe the biggest difference between the two devices is that the AKM has a more realistic, slightly meatier, and slightly more natural timbre, especially in wind and natural instruments. Although the difference is quite small, I was able to distinguish between the DO300EX and DO300 most of the time with A/B testing.

SMSL DO300EX Review
New place for the SMSL logo

Just like the DO300, the DO300EX can take your vintage speakers to a level that you would never have thought possible. It conveys the sound signature of the equipment you pair it with, without saturating or coloring it. You will also get the maximum efficiency from the equipment you are using the DAC with, which is the ultimate purpose of the source equipment.

The DO300EX can easily rival some of the pricier options in terms of technical capability. The DO300EX’s natural timbre and tonality are, in my opinion, unmatched at this price bracket. The DO300EX does not saturate but helps the equipment you pair it with shine without changing its signatures. Using my DUNU SA6 MK2 for the review, which sound is enhanced by the DO300EX even further. The instruments sound natural and as they should, without any dips or peaks, but with an amazing soundstage and resolution. My MK2 didn’t sound so good before, and I mean it.

The DO300EX’s natural take on reproduction is quite something, especially where there are a lot of natural instruments on the stage.

SMSL DO300EX Review

The integrated headphone AMP sounds magically dynamic, natural, and resolving. Sounds great with my SA6 MK2 monitors, has lots of juice to drive many headphones to the absolute max, and is friendly enough to use with multi BA low ohm IEMs like the Hidizs MS5 (5.3Ω) thanks to their low output impedance. The DO300EX has a wide and deep stage and can project the track’s stage to the listener with high accuracy. You get a clear view of where the instruments are, and there is plenty of air between them so its presentation never lets you feel claustrophobic.

Just like its ES9039Pro-powered DO300 brother, it also sounds naturally lush and full. The bassline, midbass included, is deep and pleasantly warm. This lends a slight warmth and richness to the midrange which is a welcome change from some colder and analytical SMSLs of old. This results in the richest and most natural tone timbre that I’ve ever heard on an SMSL DAC so far. But if you think that they sacrificed detail retrieval for it, you’re wrong.

DO300EX is a very transparent and detail-rich sounding DAC. This goes for clean edges and transient, but also for the rich inner-tone texture. Highs are well-extended, open, and airy, avoiding any sort of hardness or harshness. There’s nothing to complain about DO300EX’s tonality really, it’s a skillful balance between gentle warmth and transparency that provides a very natural and pleasant sound signature.

SMSL DO300EX Review
Sadly the front screen is not as large as it looks

The soundstage is very good too, DO300EX spreads and layers all tones in a respectably wide and airy soundstage. Perception of depth is not its strong suit but basically no DAC at this price point can do it much better so I can’t hold that against it. Dynamics are good and this SMSL sounds alive and engaging thanks to it. It has enough speed to follow the fast rhythm if needed but it will never sound relentless, analytical, or mechanically precise. No, DO300EX is actually a very smooth-sounding DAC that gets musical flow better than any SMSL that I have reviewed before.

The DO300EX is the best DAC under the five hundred mark, in my opinion, full stop.

Bluetooth Performance

Let’s talk about wireless performance and signal stability. The device comes equipped with one of Qualcomm’s premium-tier chipsets, QCC5125. The QCC5125 is a well-known chip and it utilizes Bluetooth 5.1. The chip supports AAC / SBC / aptX HD/ aptX LL (not present on DO300EX) / aptX (not present on DO300EX) and LDAC codecs. The signal stability was great during my time with the DO300EX, I haven’t had any audio cut-outs or stuttering. I exclusively used LDAC and Android’s audio quality priority (900-990kbps) Bluetooth mode. The LDAC range is quite good and you get no stutter up to 6-7 meters. AAC & SBC range is 10+ meters.

In terms of sound, the Bluetooth sound performance is impressive and perhaps one of the best in this price bracket. Of course, it’s not as good as wired, especially from a technical point of view, but you get similar bonuses regardless. In my experience, resolution, in particular, is slightly reduced compared to wired, and the DAC works a little harder to cope with congestion, but I don’t think there’s a noticeable difference in casual listening, although the equipment you’re listening to has a lot to do with it.

If I were to put it in numbers, I would say that wireless is about 10% worse than wired, with good enough equipment. Again, I’m talking purely about technical achievement. In terms of tonal balance, signature, etc., you can experience the DO300EX just as well on wireless as on wired.

SMSL DO300EX Review
Finally! Integrated headphone AMP.


vs. D0300

The D0300 uses the 8-Cahnnel ES9039PRO flagship DAC chip. In this comparison, I compared both products in pure DAC mode, so I try not to include the amplifier circuit of the DO300EX. I also directly connected both products to my active reference monitors, volume matched, using the same cables.

The SMSL D0300 has a better slightly low-end reproduction, tighter with more presence. DO300EX’s midrange feels realistically more natural, especially in timbre, compared to DO300, however, the difference is negligible. The DO300EX’s treble is slightly more silky, and velvety, compared to the more energetic and sharper Do300. Both of the units handle congestion-prone tracks with ease when combined with equally capable monitors.

SMSL DO300EX Review 32


SMSL has managed to improve the DO300 model lineup offering AKM’s flagship chip in a convenient package. The included headphone AMP feature was what I was missing the most on desktop DAC units and finally, we got it with the new DO300EX. This feature makes this DAC more valuable compared to the old series for sure.

With LDAC support, very good Bluetooth performance, rich I/O options, and a relatively small chassis, it is one of the best DACs you can buy in this price band, perhaps the best. If you need a versatile DAC with an excellent SQ, I definitely recommend it.


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