Wow, what a discussion... As I said, looking into the non-loaded FR of the amplifier does not necessarily show the whole picture. Do you guys have a circuit diagram of the A5? I couldn‘t find it anywhere... It‘s very possible to have an amp that will have an ideally flat responce into open and non-flat into a non-linear load... Depends on how the negative feedback / gain control is implemented...
All the cans I‘m currently using tend to bloat the bass without enough damping, particularly the Momentum in a paasive mode and the W5000. As a matter of fact, Momentum in the active mode did not show the bass increase, I forgot to mention this initially... And an active mode in Momentum of course is equal to a flat load seen by the source...
So, actually, based on this, I think this amp will probably indeed not have this bass increase with high impedance HPs, because they usually represent a much flatter load than some of the low-impedance cans...
Ok, I‘ll go listen to my new toy, actually this little Amp is really nice, my W5000 sounds with it almost as good as with the HA5000, I really like what I‘m hearing...