i got a loan set (AK120) and compared closely with AK100 , the Fiio X3 and my iphone5 - Same couple of tracks copied and i repeated the tests again with default settings -
Here's a short summary of the findings.
AK120 Observations : Sound is clean - background extremely clean and quiet , no distortions, no hiss... I'ts just done rightly , not too airy , nor too dark. Bass were well controlled and tight. Mids were sharp & clear, treble were tight. Sound overall has good slight warm and with tight impact. Sound stage : medium size - mids were centric (sound stage very similar to iphone 5 - unmodded)
Ak 100 Observations : Changing from AK120 -to Ak100 - immediately noticed that the sounds (mid/treble) sounds brighter - there's an additional sparkle on the Ak100 comparing to Ak120. Sounds oveerall were looser comparing to Ak120. After closer inspection - i realised that the Ak100 sounded thinner with lesser control - especially on the mids. Some of the tracks - the mids sounds a bit harsh - which i didn't observed that on the AK120. Sound stage : appears larger than Ak120 which is medium size - mids were not so centric
Fiio X3 : Observations : Immediately - you can get a feel of the 3D and wider soundstage. All sounds (bass/mid/treble) felt lighter. The background sound of X3 is airy and a little open sounding. Bass has similar depth , comparing to Ak120. Mids of x3 is slightly distant and softer due to the airy nature and wider soundstage. Overall x3 sounds lesser impact comparing to the Ak100,and ak120.
Iphone 5: Oberservants : extremely clean output similar to ak120 . no distortions, no hiss . clean quier background. Music has good bass impactful , tight mids - mids appear quite forward and impactful but not to the extend it became harsh. still within controlled. treble : very similar to Ak100. Brighter than ak120.
Summary : which would i prefer ?
Ak120 - would suits folks who like clean controlled sound - almost none distortions - extremely balanced - does nothing out of the norm - it will not excite you , it will not bore you too.
Ak100 - brighter signature version of the ak120 (mids/treble) all sounded brigher - more consumer style sounding - musical & fun, however sounded thinner across all frequencies
Fiio x3 - wide soundstage , airy . deep bass , excellent treble , above average mids - sound were thinner as it sounded more distant due to wider soundstage.
Iphone 5 - Just one word - musical and clean - very mid centric sounding - average soundstage. very close resemblence to ak100 - but better controlled.
Which is better for bucks ?
i wouldn't want to start a spam war by commenting on this - but each has it's pros and cons. Really depends on your earphones that you are using , any AMP or external DAC that you are going to use - or just listening it straight from the DAP. All the 4 of them are strong performers - trust me. I also had the 1st generation Sanclips.. honestly for DAP players that forummers has been raving about , the differences are mostly signature sounding and slight differences if you nitpick - more importantly , you can consider the weight , battery life , connectivity , storage options, price etc...