on a side note;
my PB1 has switches for both low gain and high impedance; I've had it on high b/c of previous headphones, (dt-880 600ohms, although vol has to be maxed for it)
I noticed when I switch it to low gain, the 'hot' treble has subsided, although to get my d7000's to a 'loud' volume i have to turn it up to max (low gain). On the high gain there is that treble hotness, but it only needs to be turned up half, about 12 oclock, for the same volume as max in the low gain.
I'm keeping it on high gain, i'm not sure if these have been fully burned in but overall the sound across the board is better than that on low. Maybe in a few more 10's of hours the treble will calm down.
on a seperate side note, the bass on these things literally make the drivers go BOOM. I've been seeing some people be concerned with a rattling in the bass, but i'm talking about the headphones physically bumping back and forth if turned up loud enough, enough to feel from the outer enclosure if you put your finger on it. I only turn it up this loud for a few seconds at a time, but will that damage the drivers?