Sony MDR NC-033 earbuds issues

[walkmanforever]

These are the supplied ones that come with the walkman NWZ A845.Since lately i've found that the earphones lack some clarity in the high end. I listened to it first at VPT (off), it was good, then i gave a listen to the other modes esp. the STUDIO mode and i found that the clarity was great! the cymbals sounded precise and clear as i'm mostly into classic rock. Then i plugged in the Creative EP-630 earphones( which handle the high frequency well for the price they offer) and i found that the high frequency in the STUDIO mode felt quite harsh while when the VPT was off, the balance was good compared to that in the supplied ones. Did I get a faulty piece or they're just like that only? Anyone associated with such a problem? Replies are appreciated. thanks!