iBasso P2

I received the P2 at the beginning of January. Out of the box I really liked its good finish, and footprint was smaller than I expected. It's a very fine looking portable amp, and is very sturdy.

Being a "portable" guy, I have listened to the P2 with three IEMs: a difficult to drive one (Apuresound ER4S); a crappy one (JVC FX-55); a good sounding, bassy one (Superfi 5 Pro recabled with Westone ES cable).

I have burnt in the P2 for a month, mostly listening to music, but also leaving it playing overnight. I've always used the 100 ohm Ety ER4S as load. Total number of hours is 250, and I keep playing with it.

This review has been done using the Apuresound Etys (wich are a recabled version of Etymotic ER4S, by Head-fi member [AK]Zip), apart from some experiments with the other two IEMs.
The P2 does its best with ER4S. Sound signature-wise, the iBasso is warm, full sounding, has pronounced midbass and slightly subdued highs. This frequency response matches incredibly well with Etymotic, which by themselves are bright, thin sounding and enormously detailed.
My P2 started to show its warm character after about 150 hours, while earlier it sounded more neutral and didn't settle yet to its definitive tone. Regardless the subdued highs, the overall detail this amp can provide is awesome. There are so many layers in music, that it's like listening to many different songs at the same time. This feeling of an "orchestra" is improved by the extreme sense of space and instrument separation the P2 is able to provide. The ER4S, thanks to their own speed and ability to separate instruments, do a their part in underlining iBasso's qualities.
I've listened to rock, jazz, classical, and each of these genres were very good with the P2-ER4S combo. The P2 makes even '60s-'70s rock music very pleasant, and has a forgiving attitude to the recordings, so that Etys are hardly harsh with any albums.
The album I had most trouble with is Charles Mingus' The black saint and the sinner lady, which is very difficult to follow and sometimes shrill sounding.
Depth of soundstage, instrument separation and imaging are enormous.

The bass boost switch is very well implemended and tight (at least with Etys, which don't have any midbass to start with). Bass is very clear and detailed. Bass can't be "felt" with Etys, like with Triple fi, but it has enough presence to became one of main characters of a "rock orchestra".

With JVC FX-55, the iBasso outputs tons of midbass, but I think this is the behaviour of the JVC's by themselves.
Using the P2 with the recabled Superfi 5 Pro improves warmth and bass presence (bass boost is off). Soundstage increases in width and especially depth.

Overall, I think the P2 is great bang for the buck, and it's a monster when matched with neutral cans. I intend to buy an AKG K500 and try it with the P2. The P2 is so organic it will help enormously the neutral K500 to sound more "fun", and bassy.
Bassy IEMs might find a better match in Headamp Pico or Lisa III (which I have not heard), while neutral IEMs like Etys, Shure SE310, Q-Jays and such are a great match for the P2.
I plan to try more neutral opamps and see how the P2 behaves: different opamp choice might make the P2 so flexible that I won't need any other amps in future.

For the record, I find the P2 to be much more awesome with ER4S than the two Xin amps I've had. The P2 is more clear and spacious sounding, making the songs bigger and richer of details and tunes. The three position bass boost also adds a lot of options to play with.

P2's only limit for me is battery life, which being rated 10-14 hours leaves something to be desired. Anyway, since I don't have to change AAA batteries (the P2 has an integrated lithium battery), to plug it into the charger overnight is not a big deal.

The most fun feeling I had with the P2 is that it really makes a difference in sound, while I have never felt this before. I always preferred to try different players and headphones, but wasn't a believer of sq improvements with portable amps - mostly because I use IEMs.

Tony