During this test, I was using Traillii for my critical listening and comparison because I’m intimately familiar with the sound tuning of these IEMs, not because of their price tag (just saying). Each of these dongles, besides a difference in tonality and pair up synergy, has their own Pros/Cons when it comes to features, all of which should be taken into consideration depending on your priorities.
Also, as a little side-note. While many people will be curious how S2 compares to other usb dac/amp dongles, such as W2 and RU6 I, I’m sure some might be curious how S2 stacks up against some of the DAPs. Unlike S1 where I felt there was a bigger gap, S2 actually sounds closer to Lotoo’s own PAW6000, both in sound signature and technical performance. Of course, it will depend on pair up synergy and the type of IEMs or full size you are using, but with a number of IEMs while doing volume matched A/B comparison, I found S2 to sound relatively close to its bigger brother, PAW6000.
Furthermore, there are many dongles in the market right now, but I will focus in my comparison on S2 vs S1, W2, and RU6 due to them being in the same class with more advanced features.
S2 vs Lotoo S1 – Right away I noticed a wider soundstage with the sound literally spreading more to the left and right. Both have a good imaging with convincing placement of sounds in space, but wider soundstage of S2 gives the sound a more holographic imaging. Another change is in tonality, especially mids/vocals being more revealing, more layered, a little more forward in S2. Treble sounds the same, a natural sparkle in both, but mids in S1 are smoother, warmer while S2 is more revealing, more micro-detailed, and with better layering and separation of the instruments. In my own personal opinion, S2 upgrade from S1 is well worth it. And addition of playback control button is priceless.
S2 vs L&P W2 – W2 has a touch wider soundstage, just by a bit, while the imaging and the sound placement are quite similar. In terms of tonality, W2 mids/vocals are a little more neutral in presentation and brighter in coloring, while S2 has a fuller body and a little warmer tonality. With treble, I also hear a little more sparkle and air in W2 while S2 is a bit smoother. The gap in tonality between S1 and W2 was more noticeable, while with S2 it is closer, though S2 is still a little smoother and more organic while W2 is more revealing which makes W2 sound a little more detailed and resolving. Depending on your pair up synergy preference, especially with warmer tuned IEMs, W2 could have an edge due to its higher resolution tuning, but in terms of functionality and features (remote playback, LO, MQA, less current draw) S2 has an upper hand there.
S2 vs Cayin RU6 – RU6 soundstage spreads a little wider and imaging is more 3D. Doesn’t mean that S2 has narrow soundstage or congested imaging, it is still wide, but RU6 stretches and pushes it wider. Both S2 and RU6 have a more natural tonality, but S2 sounds a little more organic with a fuller body while RU6 is a little more revealing, more transparent in mids, and has a little more forward sound. And the same with a treble where both have a nice airy sparkle, but S2 is a little smoother while RU6 treble has more air and crunch. The difference between S2 and RU6 has less gap than with W2, and it puts RU6 between S2 and W2 when it comes to tonality and resolution. In terms of extra features, S2 does offer more.
In general, for some the decision of choosing either S2, W2, or RU6 will be based purely on sound tuning that going to affect pair up synergy. For others, the functionality and extra features will be a deciding factor depending on how you use the device.
There is no denial, S2 has Lotoo’s DNA, both when it comes to a sound sig and a technical performance, even coming closer to PAW6000 DAP when using IEMs. And while I don’t think usb dac/amp dongles going to replace higher end DAPs, they do offer a great opportunity to convert your smartphone into the higher end streaming DAP instead of dragging a DAP in addition to your smartphone. Also, a device like S2 will be great to enhance the sound of entry level smaller DAPs, since to unlock full S2 potential all you need is a digital source while this dongle does its own decoding, processing, and amplification into SE or BAL outputs.
But besides its audio performance, which some can argue to be subjective relative to pair up synergy, what really makes S2 standout from the crowd is the set of its features. Having both 3.5mm and 4.4mm outputs is convenient, and ATE/EQ effects add a nice coloring touch to the sound when, for example, streaming movies. Then, having Line Out is a step forward to keep the sound clean when using external amplifier. And its belt-clip accessory with a bonus extended cable is a clever way to keep the smartphone in your pocket or backpack and to secure S2 for easy access of remote playback controls, one of my favorite features since you no-longer have to take your phone out of the pocket to turn the display on if you want to pause or skip a song.
And to answer the question I raised in the intro of the review, I do find it a no-brainer upgrade from S1 since there are improvements in everything from the sound to the design, operation, and included accessories. My only sincere wish is one day for Lotoo to consider the enhanced version of their dac/amp dongle with addition of Bluetooth wireless functionality.