Jimster480
Headphoneus Supremus
Have you left it on since you got it?Bifrost Multibit > Jotunheim > HD650 (balanced) and HE500 (balanced).
On initial listen the amp sounded quite dark. Also the soundscape sounded very left channel, right channel centric. My initial impresseion was that the amp sounded very strange so I just left it on all day and night fed by a source in continuous play mode. The next morning I gave a listen and the soundscape was noticeably more expansive with considerably more detail, almost a bit bright sounding compared to initial listening. Over the next number of days the change wasn't as starkly noticeable however the amp seemed to settle in nicely becoming cleaner more refined sounding. When I push the volume up the headphones sound very clean and there is no harshness to the sound (unlike the Magni and Magni 2U I owned earler). I can attest that the HD650's do indeed scale with improved amplification as they sound very good indeed with no hint of veil in their signature (once again, unlike my first Magni).
Call it what you want, burn-in, breaking-in period, settliing-in...whatever? All that I can say is that there was a noticeable (and memorable) improvement in sound quality with this amp.
If you turn it off for a while and then turn it back on, how does it sound?