I have a good quality mp3 collection. mp3gained to a satisfactory level. My clip zip is set to the right zones and is NOT quiet. What I have noticed is despite all settings being correct, when plugged into an aux port to car stereo, boom box, and so on an old ipod or new smartphone sound maybe 20% louder. I would imagine this also holds true for headphones but might be less noticeable. i.e. clip zip sounds GOOD and loud enough maxed out where MAYBE an ipod or other device simply goes louder.
Case in point: I work in a high noise enviornment. Several of us have different models of work radio (dewault, milwaukee, bosch). On every one, their old ipods, new ipods and other devices can be heard from further away without being drowned out. They just go louder.
I have had several clip zips and the same story each time. Without another eq option to “boost” bass/treb my music cannot be heard.