Here is my "concise" comparison of several USB DACs and related sources, definitely biased, but purely from a personal perspective rather than “unbiased reviews of free samples”.
Apple USB DAC – Sound: 4.5/5; Overall: 5/5
The Apple dongle is just unbeatable to power most of IEMs at $8, if to think about it - some Apple pun on HiFi World, especially considering typical Apple prices. Clean, quite powerful, less colouring than most of the “HiFi” DACs. Not to take for granted for all simple USB DACs. Gor instance, most of my initial Amazon $10 purchases were unfortunately strongly hissing and hardly useful.
iBasso DC04 – Sound: 4.5/5; Overall: 3/5
Worst compatibility that I ever experienced – only 2 out 5 of my household devices worked right away. The cables became dangling on both sides - not life threatening, but hardly nice. So no iBasso anymore for me. The sound is fine, very close to E44, but overall just for $15 more, E44 is so much of a better choice, in my experience.
Shanling UA2 – Sound: 4/5; Overall: 3.5/5
Unduly warm, perceivable background noise with ESS 9038 (!); heats up notably; colouring. Overall, it clearly defeats the point, in my limited opinion, especially for the asking price. Furthermore, after reading the UP5 thread, with all the user troubles and the statement that 40%-ready software is OK according to a Shanling representative – Shanling is banned from my limited universe.
Tempotec Sonata HD pro – Sound: 4.5/5; Overall: 4.25/5
My first USB DAC that came bundled with Tempotec V1A. At first, I found it very “clinical” after my warm DAP. It grew on me to appreciate clean and clear Cirrus implementation. Arguably, a very good value, I am just spoiled to prefer E44.
Tempotec BHD –Sound 4.5/5 (subjectively, for all-BA IEMs; less for DDs); Overall: 4.25/5
While I can understand BHD limitations and overall more reserved opinion about it, BHD worked very well for me in combination with my several bright and agile all-BA IEMs, becoming my softer USB DAC of choice. BHD definitely softens the sound, and may not be the best choice with DDs, especially warm ones.
Tempotec E44 – Sound 5/5; Overall: 4.75/5
My personal favourite of all by sound, compatibility, aesthetics, and the ease of use. The balanced-unbalanced connector is also quite unique and nice. The only shortcoming perceived so far is somewhat fragile cables (BHD cable feels better). The sound is very open, dynamic and not much colouring (?), while more euphonic(?) compared to the Apple dongle.
Fiio BTR5 – Sound: 4.75/5 (in a DAC mode); Overall: 4.75/5
Really great by virtue of its quite neutral sound, very good power, nice compatibility and functions; never had problems with connections, operations, etc. Sounds the best in a DAC mode, but then the battery life is limited in a balanced mode, and the BT connection is not perfect. I would love to see BTR7 with a better battery, better BT range, even without a substantial DAC chip upgrade.
Fiio BTR3K – Sound 3.75/5, Overall: 4.5/5
Really cute, nicely functional and not the bad sound, though AK4377 are quite lame to my ears – both in BTR3K and especially in Tempotec V1A. (I do have strong idiosyncrasy with AK, AK4393 USB DAC was the only AE item that I had to return, perhaps a defective one, either by manufacturing or by the very design…). Back to BTR3K: great battery life and better BT range compared to BTR5. Very utilitarian.
E1DA SG3 – Sound 4.75-5/5 (w and w/o battery); Overall: 4.25/5
After initial WOW, the reality was a bit more sobering – needs some external software to manage the sound, pops up, notably hissing background, after ~2 minutes of not being used switches to hissing. It does require an external battery to sound it very best, another notable limitation. Though the ability to power iEMatch without much of the notable change in sound is totally amazing (!) and highly respectful. So for the sound above the convenience and relative value, it may be called “the best”, I can concede. At the same time, at $100+ with the additional software for $10 (strange and uncommon solicitation), the value proposition is arguably not exceptional.
Hiby FD1 – Sound 4.25/5; Overall: 4/5
An odd one, the form factor really did not work for me at all – surprisingly inconvenient. The sound is quite neutral, not offensive, but not exceptional. Two good short USB cables and the sticker happened to be more valuable to me that the unit itself. After some conversation to Hiby, when instead of trying to help me with the compatibility, all they could do is to push R2 - Hiby products are banned for me as well.
Conexant CX31993 – Sound: 4.25/5; Overall: 4.5/5
Feels more cheerful, compared to the Apple DAC, more emphasized treble; may work better with single DDs, especially warmer ones. Due to colouring may not be as universally recommended as the Apple dongle, in my opinion, though the value can be arguably similar.
Fosi HD pro (DAC/Amp) – Sound: 4.5/5; Overall: 4.5/5
Most brutal (unaltered(?)) implementation of ESS9038 that I have encountered . Some background noise is clearly apparent. I used it quite a bit for comparisons; can be very useful when a battery-powered DAC is needed.
Zishan Z4 (DAP) – Sound: 4.5/5; Overall: 5/5
I bought Z4 out of curiosity, worked perfectly so far, and amazing value! Quite direct implementation of ESS9038, some circuitry noise and some interference in the BT mode (all minor). The sound is somewhat with a bit more emphasized bass, so a touch softer/warmer compared to Fosi HD pro.
Lastly, Fiio Q1-II does not feel competitive to me anymore in the context of this comparison due to an overly warm nature and quite strong background noise; especially in the DAC mode (the amp mode is notably better and more useful).
Finally, my old DAP, Pioneer XDP 30R, being quite on a warmer/softer side, but with zero background noise is still much competitive by sound and remains of a somewhat unfulfilled conquest to match (habits, subjective preferences…)
So overall, if I were to keep only one USB DAC, it would be Tempotec E44. If I had to choose the most value – Apple USB DAC, undoubtedly. Sonata HD pro almost fits in-between along the price/value ratio. E1DA SG3 could be an option for the power above all. Fiio BTR5 is a very good BT source.
P. S. Edited for typos
