For about 3 4 hours on YB04. I use it direct on my apple dongle for a clean output for a better comparison with my other iems since apple dongle is my main benchmark. To be honest, YB04 easily sits on the range of ier M9 and Rai Penta. First impression; YB04 vs M9; yb04 is noticeably wider and more controlled bass. Details pickup seems a tad bit superior than M9. M9 is deeper with noticeably narrower except when M9 with RE Hifiman tips which is big big bore. YB04 vs Rai Penta; iirc the mids on penta is really organic, life-like vocals representation. To me YB04 has almost the same representation. Almost life-like. What makes this set better is the staging and highs. Better pin point and more details in highs region. More listening to jump onto conclusion. I would say, yb04 is a serious set. Not a hype but a true set to keep. edit: im scared; this set has a potential to dethrone my fav M9 for the neutral and life-like vocals representation due to better soundstage (width) and more controlled bass.