nah, they're all a bit easier to drive than the HD600, but the DFR had plenty of juice for all of them. If anything I kind of wish the DFR had a low gain mode, because I was on the very low end of the volume with all of them.
So even with a HD600 the gain is too high ?
After owning a Dragonfly Black for three weeks the only thing I would like to change is their gain, the high gain makes volume adjustments, escpecially on iOS, very tricky with my low impedance headphones. I would really like to buy a Dragonfly Red, but I'm afraid that their even higher output will make finding the perfect listening volume almost impossible for me. If they release a firmware update where we can reduce the gain I will order one immediately. For my headphones I would be happy with 30% of what it's now.
I really hope this is something they will fix in a firmware update...