S.M.S.L released their latest flagship model DAC the SMSL M400 on May,2020. The M400 is the flagship model of Desktop DAC’s from the brand’s highly acclaimed “M” series of desktop DAC’s.The SMSL M400 features a flagship-level DAC chipset using high performance AK4499 DAC chipset with a powerful USB receiver chip from XMOS. It supports full MQA support offering the users with the best of the sound quality output.

Six month later, S.M.S.L SP400, the upgrade generation of the SP200, was released. It also houses a premium THX AAA-888 amplification circuit and has impeccable audio performance with a super clean background and super-powerful output. SMSL has designed the SP400 to pair with the SMSL M400 their latest flagship MQA DAC system. You also can pair it with any DAC system of your choice. 

With the release of SP400, meaning that it’s the first true balanced input to output AAA-888 amplifier. SMSL is targeting the top of the field and all the buzz it is generating amongst the audio community. We are compiling the reviews of SP400 from famous bloggers, influencers and reviewers and we are going to share with you right here.

Video reviews round up:

Tharbamar youtube channel posted a video review of the S.M.S.L SP400 on Jan 16, 2021：

So I also tried a few different headphone amps and this is the one of the quietest headphone amplifiers that you can have. It is very quiet, I mean the background noise is, as far as I can hear, non-existent.

Next thing is i also tried this headphone amplifier pre-section. As pre-amplifier pairing with my old denom serving as a power amplifier and it sounded very very nice it's very clean and naturally reproduce tone and sound signature with very musical overall engaging sound. When i'm using as a pre-amp using the balance to rca adapter to connect to my old denon amplifier with a balanced input from maruan's sacd player so this is the input this is the output that's very simple setup this kind of adapter will get the job done if you have the amplifier without the balance inputs.

Very balanced sound signature from top to bottom, nothing overly exaggerated frequency range mid-range to highs everything is well behaved and really good balance which is I think that's the highlight of this headphone amplifier.

As for the tech inside it sp 400 is the fourth thx 888 equipped headphone amplifier on the market. But the absolute first one to have four modules instead of two as such it is the first true balanced input to output amplifier having these particular modules, so i should definitely hear an improvement over the sh9, and who knows maybe over hpa4. As well the analog section of sp400 is looking exactly like a double version of sh9 and as such it offers double the power more exactly 12 freaking watts into a 16 ohm load. All that power will mean nothing if there isn't a wide bandwidth to deliver all that instantly to your headphones. Its bandwidth extends from 0.1 hertz to over 500 kilohertz meaning that sp 400 will deliver an instant amplitude and should have a perfect phase accuracy.

Article reviews round up:

Audio Science Review posted SMSL SH-9 THX Headphone Amplifier Review on Jan 13, 2021:

As you see, there are no controls on SP400. Everything is menu driven including input selection and gain. If you use multiple headphones with different gain requirements, having to switch that using the menu can be a bit of a hassle. Fortunately there is a mitigating factor as you will see in the measurements.

One main distinguishing feature is that there is remote control and relay based R2R implementation. This should assure very good channel balance -- something that we will check later. It costs a lot to implement this feature though and that is reflected in the cost.

Some other amps that get the best signal to noise ratio (and SINAD) tend to have a low gain mode with better performance. Here, the three modes are almost the same so I would just use the highest gain setting and be done with it. It is not like it impacts the channel balance as you will see later.

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SOUNDNEWS' wirtten review on S.M.S.L SP400 :

With SP400 you’ll be listening to the source material first, then to the source itself and only then to your headphones. It doesn’t leave a stain on your music, it simply wants to disappear from your acoustic chain, without adding or drawing anything from there. I’ve a tried tens of headphone amplifiers by now and I still have the most respect for those that are not staying in the way of the acoustic signal. With an amplifier like this, doing DAC or headphone reviews becomes a whole lot easier, because I would be listening to the acoustic chain and not to the amplifier itself.

Apart from this, starting with IEMs and finishing with notorious headphones like Hifiman Susvara, SP400 was pumping a high engagement factor, it had a very high level of detail, offered an open wide soundstage and it had one of the best diaphragm control I’ve experienced with headphones. It stood shoulder to shoulder with my Benchmark HPA4 and it even outclassed it on several occasions, while costing about ~5 times cheaper.

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