Using on iem's on desk. It's powerful on low gain, never reaches over the 12 o'clock position for most of my iem's, in which I tested around 25 of them on. The sound is clean, unless you turn on the bass, which is slightly warm with a nice boost over all frequencies, it's certainly not bloated, I like that! It brought 2 iem's to the forefront which really surprised me(Pretty much stopped listening to these two until now). It greatly improved the ikko 01 and the Brainwavs B400 to which I really enjoy them even more. To my surprise also, my favorite iem's I listen to on my FiiO K3 didn't sound too good on this, my CVJ's, it brought out too much sharpness in them, on the Blon 05's you can really hear the slight muddiness on them, but still sounded good, which tells me this amp is really good in the clarity/clean department and that it will bring out and emphasize the good and bad on iem's. The filters, not very much difference, but I stick with "1(Seems normal) & 3(Seems like a slight sub-bass increase)." #2 seems slightly warmer, but it's so slight on all of them it's really hard to tell, have to really listen to super heavy bass tracks to get an idea of what's what. Battery last for around 5 to 6 hours, never has died on me for a music session, charges with the cell phone block quickly.
Negatives: C-type cable had wires exposed in the joint area. Can't see placement of volume on knob in low lit room. Side buttons need some color to see.