PerformanceEarbuds like the AS-Charms are made for use with a solid performing DAP or alternatively a DAP in conjunction with an amplifier. They are quite hard to drive for the average DAP. When driven by an iPhone 4 you have to push the volume to over 50% in order to get a decent level of volume with most ordinary masterings. The Head-Direct HiFiMAN HM-801 can easily power them with the normal amplifier module to great results. Lack of amplification is easily remedied by the use of a headphone amplifier. The Sunrise AS-Charm earbuds sound really nice even with not so high end headphone amplifiers like the FiiO E1 and E5.
Before any real testing was done the earbuds were allowed to burn in for 150 hours.
The earbuds were tested on the following rigs: Cowon D2, HiFiMAN HM-801 (standard amplifier module) and via line out to FiiO E1/E5 and RSA Tomahawk, and last but not least on the iPhone 4.
It is clear that the Charm earbuds sound better than the Feeling even on a modest DAP like the Cowon D2. As you progress up through the rigs it is clear that the earbuds are held back somewhat by the amplification quality. The benefits from additional amplification beside an increase in volume is that the bass and midrange become more in-line with each other and they gain a little speed. Compared to the highly regarded Yuin PK1s the Sunrise AS-Charm has a slightly more laid back sound signature, but detail wise they are very much alike. To these ears the Sunrise earbuds sound like a different flavor of the Yuin PK1s which is a good thing.
The AS-Charm sounds like a bettered version of the AS-Feeling when driven properly and bests the AS-Feeling in every aspect right from extension in both ends and when it comes to definition across the spectrum. The price difference between the two is huge, and you have to have a good DAP in order to power them right. For everyday use I slightly prefer the AS-Feeling because they do not need an amplifier and can be powered well straight out of my primary DAP. However for more serious listening sessions the AS-Charm's increased definition and somewhat warmer sound signature makes them the go to earbuds.
On a side note the Sunrise AS-Charm do not sound odd in the lower bass register to the same degree as the Yuin PK1s. There is minimal difference in sound between the two which makes me wonder.