ATXBBCHad to dig through your posts to find out what's wrong (I'm free because of lockdown anyways).
Tl;dr, you claimed these sound horrible, can't drive your cans, and [its battery] died after a few months.
While I can't argue that dying batteries isn't a concern, have you ever used the companion app?
ATXBBCDamn, that must've sucked. Did the x2 current for 3.5mm/x2 voltage for 2.5mm settings not help with driving cans at all?
I'm looking into higher-end headphones, so I'd like to ask which cans did you try to use with the ES100 to see how far I can push it.
NEXONUSSennheiser HD660S, Focal Clear, Campfire Cascade, Mr. Speakers Ether Flow C. For something portable in the $100 range, I recommend the Fiio BTR5. I own 2 of them so I can swap them out when charging and they are fantastic. Balanced, they drive all the cans mentioned above reasonably well, though there is still a slight bump in imaging and sound stage when switching to desktop amps like Fostex HP A4-BL and THX AAA 789. I also have Campfire Andromeda, Atlas and Solaris as well as Audeze iSine 10 that sound great through them.
ATXBBCI'm tight on money but right now I own:
HE-4XX: treble's a bit harsh on some tracks but overall pretty great
99 Noirs: relaxed and warm with a hint of sibilance; not very detailed but smooth is nice too
M40x: too intimate/very narrow stage; sounds somewhat "dead" despite being a slight "V"
I'm saving for the new HD560s as soon as a local retailer picks them up.
NEXONUSI have tried the 560s. They are excellent. I'd pick them up if I didn't already have 660s. My Cascades replaced 99s as my intentionally warm pair, but I liked the 99s. Great selection!
ATXBBCBecause it's a balanced Bluetooth DAC with LDAC, for $80 it's an amazing bit of kit for cheap. More than that I can hook it up to my balanced portable tube amp, and still use my phone.