@ manhattanproj- I don't own the K701 if that was directed at me.
I'm using default op-amps. I haven't tried any others and honestly haven't learned enough about the subject to explore this further.
I no longer own any Shure IEMs but with my ER4P these are my findings:
AE-2/high gain with no source connected: hiss barely becomes noticeable at 12 o'clock, easily noticable at 2 o'clock.
AE-2/high gain with iPod connected via ALO Bling Bling LOD: (track in pause), hiss becomes barely noticeable at 10 o'clock, easily noticeable at 12 o'clock. note- with track playing, my normal listening volume would be around 8 o'clock and 9 o'clock is an estimated 85 dB.+ (track was "Follow Your Leaders" from The Tangent).
AE-2/low gain with no source connected- at 2 o'clock I could barely hear hiss and this was very slight(it took a dead quite bathroom to discern), at even maximum volume (5 o'clock) there is virtually no hiss. The only noise that I heard was a slight scratchy hiss/pop as the volume came down from 5 o'clock- this was heard at 4 o'clock as I was quickly turning the volume down.
AE-2/low gain with iPod connected as before(track paused). At 12:30 o'clock hiss becomes barely noticeable, easily noticable at 2 o'clock.note- my normal listening volume would be around 10 o'clock or less. At 11 o'clock loudness is an estimated 85 dB.+. The track listened to was "Up-Hill From Here" -The Tangent.
These comments were typed as I ran through these tests.