Are you able to try the card in a different player to see if it behaves similarly?

I just drag and drop the music files/folders on to the micro SD card (in a card reader) and then insert the micro SD in to the AP80. Never a problem. Have you tried taking the AP80 out of the loop?

Totally this! (Above) Investing in a better op amp will really open up your DSD it will likely play ask important role in improving the sound. There’s way more to a DAP than the DAC.

The Z2 can be used as a DAC,but not an amp.

Depends on what you want out of it. The F2 is a bit more flexible as a DAC and a headphone amp, as well as being a player. But beware, the F2 will only play mp3 and wav.

I don't think your experience is that unusual - which is a shame as the 115 has an engaging sound signature, so much so that despite its flaws it remains one of my favourite DAPs. For its price, there is nice clarity there. I have BLON 05s too and it's rare that I'll ever drop down to a volume...

Sorry - I didn't read the title properly :)

A bit of a cliched response, but BLON BL-03?

How about the Zishan Z3? A little over your budget, but real bang for the buck. And it has a screen. :)

It's good to be a part of this forum after having spent months as a lurker gathering information. Hopefully I'll be able to contribute and help others soon, as others have already helped me. :)