What is causing this, i don't have a dac. 320 files play fine, but 24 bit just have a hissing in the background. Also they have this on my ipod classic (no dac)
Hiss when playing 24 bit files through computer and headphones?
Your PC may not have a 24 bit capable DAC chip inside of it also explaining the hiss. PC listening is almost always terrible unless a good soundcard or external DAC is used.
Out of curiosity how are you creating / downloading the 24 bit music?
I am downloading them from various sites, then converting them using DB poweramp to apple lossless. However the file before i convert it still has the hiss.