When I bought the Predator in early June, my previous experience with a portable headphone amp was with the Headroom Total Airhead, which if I remember correctly, I bought around 2006. I had many hundreds of enjoyable hours but I was looking for something a step up in term of sound quality. This is not a blow at HeadRoom, I loved their product since day 1 and would continue to do so if the upgraditis bug hadn't hit me...
I knew about the long burn-in time of the Predator, before making my purchase, and knowing my music listening habits I figured it would take me a year to fully enjoy the final sound signature of the amp. It's been almost 3 full months and I have around 300 hours on it. I can say that for some reason, sometimes the sound quality would be, erm, "weird" (like, little soundstage, very dull sounding) but then everything would come back on track within an hour or so. But the thing is, from Day One, this amp stroke me as being incredible! Loved it instantly.
Now, after the amp upgraditis bug hit me, the earphone/headphone did too and right now I am mostly pairing my Predator with the Yuin PK1s. There are 2 problems with this. 1) Apparently, from Yuin's own forum, the PK1 takes 500 hours of burn in time. If the sound coming from either the Yuin or the Predator gets any better than this combo is giving me right now, while they're both still burning in, the audio industry will lose a customer
2) I'm not sure I can tell which is getting better over the burn-in period right now
Anyway, early on, I decided to enjoy the burn-in process while listening to music (which in the end, should be done around May of 2009 :O ) and I don't regret it one bit
It's only at 300 hours, it's an amazing sounding amp, and I am very happy with it!