I traded an IEM recently to another member in exchange for his barely-used PPAS, which he got from the builder FallenAngel. (the guy I traded with bought an ibasso D10 for the dac/amp combo) I've tried the amp out a bit with my ATH-ES7, and I'm really impressed with the effect. But the ES7 isn't exactly a difficult headphone to drive, and I'm interested in knowing what this amp can drive. The specs for the PPAS: LME49720/LME49710 opamps, 3x buf634 buffers, gain of 5.5x, currently powered by a 270mah rechargeable 9V. What are some suitable circumaural cans that this little amp would light up? Dt880-250? K702? HD600/650???? I know this portable amp might not drive such headphones to their best performance, but if it can at least drive them somewhat decently it would give me an excuse to take a first step into some better gear. Or would it be better suited to the SRH840, or a Beyer 32ohm Dt770 or 880? And with that gain, would this amp also be suitable for high-end IEM's, or would it be power overkill? Thanks for anyone who can provide an experienced reply. I'm a total newb to portable amps.