SMSL DO300EX Headphone DAC/Amp Review

The DO300EX is an all-new all-in-one DAC and Headphone amplifier from SMSL and is a nice little unit that retails for $469 on Aoshida Audio (

This review unit was sent to me by Aoshida for review. (

The DO300EX is the next in the line of the DO/HO series of DACs and Headphone Amplifiers from SMSL but this unit combines the DAC and amplifier into one unit, making it a small and powerful little product that includes the best of both worlds.

The DO300 EX features the AK4191+AK4499EX DAC chips, which are the flagships from Japanese manufacturer AKM. The unit also uses the 3rd generation XMOS XU-316 controller.

The back of the unit features USB-C, Optical, Coaxial and I2S inputs, giving this a wide array of digital connection capabilities.

To round out the digital side, SMSL included Bluetooth 5.1 support with the Qualcomm QCC5125. This unit supports the full gambit of Bluetooth protocols: SBC, AAC, AptX/HD, and LDAC CODECs.

On the analog side, the unit features the Texas Instruments TPA6120A2 amp chip. This DO300EX can output 1W at 32 ohm though its single-ended 1/4 inch headphone jack or its Pentaconn 4.4mm jack. In addition, there are both XLR and RCA outputs on the rear that makes the DO300EX and powered pre-amp.

The unit also has an included remote control that is quite standard and familiar if you've used SMSL or Topping products before. Its a nice feeling, and lightweight remote that helps you quickly change volume, and scroll through the menu display on the front screen panel to adjust various settings.

The settings on this colored display include input/outputs, gain, digital filters, and also some custom tunings that adjust "Sound Color." This Sound Color menu has various coloration profiles and levels to adjust and play with and makes subtle changes to the presentation. I like to enable the Rich setting to give a little bit more body and just ease off on the sometimes sterile sound of the stock setting.

Sound Impressions

The DO300EX is an enjoyable set. It had a clean and detailed presentation that did not seem overly flat or clinical, but had just enough subtleness to it that I did not feel fatigued when listening. On some of the more recent headphone DAC/Amps from some of these companies who reach for the utmost measurables, I always feel like the clinical and ultra incisive sound ruins the enjoyment of music for me. I don't feel this way about the SMSL DO300EX luckily.

I tried an array of different headphones and IEMs with this unit and I didn't seem to have any problems with any of them with power requirements.

For IEMs, I used various recent IEMs like the Subtonic Storm and Symphonium Crimson, along with the Hidizs MP145 and Shanling Sono, and neither of these struggled with the DO300EX. The hardest to drive of these IEMs is the Storm, and I had no problems getting this particular IEM loud, albeit with high gain activated. The Storm didn't sound quite as dynamic and punchy as I'd like, but it was very resolving and sounded quick and agile.

With the more sensitive IEMs, I did not hear any amplifier noise or hissing on low gain, with music off. This is always something to be wary of with desktop amplifiers and sensitive IEMs, but for what I tried on this unit, it did not present any noise. These are not the most sensitive IEMs to noise however, but I did not have items like the Campfire or Vision Ears products around, which are more prone to this.

Moving to over-ears, I mostly tried this unit with the Hifiman HE400SE and the NAN-6 planar magnetic headphones. I did briefly play the Sennheiser HD600 on the unit as well, but the majority of the time was spent with the harder to drive planar pair.

Both of them required me to activate high gain for proper usage. I used this DAC/AMP in the office, and when on conference calls, for example, it would be sometimes very hard to hear my colleagues speaking when the amp was set to low gain (when I was using it with IEMs), but a switch to high gain resolved the problem easily.

The HE400SE, as many Hifiman products, can be a bad pairing with an amplifier that is naturally brighter or at least very neutral. In my experience, I like using it with warmer amplifiers and ones with sufficient power to not make it sound sharp or fatiguing. I would say that the experience listening with them on the DO300EX was mostly good.

I listened to a lot of shoegazer and indie rock lately, with sprinkles of americana folk and progressive bluegrass. Some of this music can get fairly bright with the amount of stringed instruments going on at once, but for the most part, the pairing of the Hifiman headphone and the SMSL DAC/Amp provided a nice to listen to presentation that did not cause me to take the headphones off. This has happened before when I used it with Topping amps...

The overall presentation of the SMSL DO300EX is what I'd say dead average. It's not a big wide presentation, but its also not a very intimate and foward sound that I really dislike -- one that makes all the dynamics go flat. I'd say it sounds like it should.

Final Thoughts

The DO300EX is a nice and attractive looking headphone amp and DAC. It has a lot of features and connections that should make most people happy as well. While it's not the most exciting or warm sounding amplifier out there, it does go right down the middle in neutrality without coming across as being too clinical. 


  1. I'm considering purchasing this unit. In the future it would be helpful if you connected up the unit under review to a speaker system so that just the DAC can be evaluated.


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