Excuse the large letters, but with what music and at what approximate listening volume (low/medium/high) out of what gear? Music and volume make ALL the difference. I have cheap IEMs that sound fantastic at low and medium volumes to acoustic music, and fall apart quickly after that, or sound harsh and awful with modern pop and electronica. I've asked you to state this kind of thing before. Please do so for the sake of everyone. Just "They are great" or whatever...
Shamelessly pinching this post of high-end DAP impressions for here, as it is interesting (I haven't spent time with the AK300 or AK320 yet). I'm at the point with the X7 that I reckon if someone made a HM901-style balanced module for it (with OPA627s), that would be the best of both worlds, even if the X7 is a bit behind in detail retrieval.
I second the 5760 tube recommendation. That was an absolutely gold find. I tried it with an adaptor in another amp that uses a 6SN7 for gain and it was just as good an upgrade. I tried a couple of very neutral-sounding 6SN7s in the Vali 2 but I reckon the best results come with tubes that are a little coloured, which most are.
Interesting. The M1 Pro arrived and the only thing I've compared it to so far has been the AK380, which has a wider and clearer presentation.
@Deftone I'm not getting any emphasis at any frequency, so that might be caused by using multi-BA IEMs where the high output impedance would change the frequency response.
Some people will be sensitive to subtle differences, some people wont be. Sometimes it is the music they listen to or the quality of it. Someone who listens to high-quality recordings of piano or violin may be more sensitive to these things than someone who listens to electronica for example. Some people will have the opposite opinion about which is better. You'll get every opinion under the sun. It is the result of discussion of what amounts to subtleties in an hobby that...
No, they don't make USB cables. They manufacture DACs. One just posted, yet again, about the numerous issues with USB as an audio transmission protocol on here. I don't want to post their names (both are very prolific posters) but if you want links to where they are discussing so you can read and ask them about it yourself, I'll PM you.