If you've never used a device like this before, it can significantly increase versatility. They allow you to use almost any headphones in any location. The device has sufficient power in the various modes to drive most commonly used headphones, and its sound quality sounds transparent to me. I love the knob as it's a convenient and precise method to control volume, making up for the lack of granularity in the volume controls of Android/iOS. I wonder why there aren't more robust volume controls already available. Pairing with multiple devices works well for the most part, but I have only found one way to enter pairing mode, which is by disconnecting it from any currently connected devices. It seems to have a default device to connect to, but you can easily connect it to any device when you turn it on without any issue.
The Shanling is a great alternative to the Fiio btr5, particularly if you buy it at a discount or as a used item.
The audio quality via Bluetooth is excellent, with a tendency towards warm sound. Surprisingly, the bass is controlled, which is not commonly found in a Bluetooth device. Furthermore, the highs are never scratchy, but rather refined. One drawback is that the device cannot be connected to iPhone via USB cable; although having an internal battery, it can only be connected to a desktop or laptop, not an iPad. Connecting the Shanling to a desktop or laptop results in a better quality sound. However, compared to the IFI go Link, in my opinion, it feels better in terms of dynamics, punch, and extension of frequencies across the spectrum.
I purchased these for use as subs when I go out. A potaian larger than a smartphone is not a good candidate because it is difficult to put in a pocket and walk around, so I chose to use 2.5mm balanced rather than sticking directly into a smartphone, which reduces excess sound. In portable use, unless the sound is very loud, even the best set will drown out the subtle sounds of your breathing and body movements while walking, so I prioritized lightness and not affecting the battery of my smartphone. However, when I am waiting at a traffic light or waiting for a train, I suddenly realize that there is little extra sound.
When I purchased it, only 2 types of digital filters were available, but after updating the firmware to ver. 1.3.3, 4 types are now available.
I have also read a review that it can be used with Switch, but I was able to recognize it with PS5 using the UAS A to C cable. I was using the same Shanling UA2 with UAC1 recognition, but with the UP4 I can easily adjust the volume, which is unexpectedly convenient. The sound itself is much better than the Sound Blaster G3, which is about the same size for gaming, though of course it doesn't have the gimmicks for gaming.