... to work their magic on higher impedance headphones? Case in point, I use a FiiO A5 to feed my Sennheiser HD700 with 150 Ohm impedance. I usually have the volume pot @ 1/4 the way around to get about ~70 dBr which is comfortable listening volume. However if I increase the volume pot to about 1/3 the way around, I get ~80 dBr but also the detail retrieval & sound-stage really opens up. Is this because the louder volume is allowing more detail to be presented which I'm not sure of because I listen in relatively quiet environments or is it because the higher volume allows the amp to feed the headphones more current & voltage to the designed requirements for the headphones to really sing?