“Pros: Eliminates the need to own several impedance adapters, Runs inline with sources and earphones, Incredibly smart design, Easy to use”
“What happens as a result is many of these earphones have a background hiss or will pick up digital noise. It can get really annoying, especially when trying to use an earphone of this type (or any other sensitive earphone for that matter) with our favorite portable sources like DAPs, and portable DAC/Amplifiers. If we are going to shell out large amounts of cash on a high end earphone, we don’t want to be burdened by background noise, right?…..While it does come in at a higher price than a few impedance adapters, this is a convenient product that will be a must have for those of us who have several in-ear monitors. I have already mentioned this device in several reviews. It addresses one of the main gripes people have for sensitive earphones.”
Thanks HiSoundFi!
http://www.head-fi.org/products/ifi-audio-iematch-headphone-travel-accessory/reviews/17505