Hi ,my pre was starting to shine at 400 hours,at 450 it is still getting better and sounds alot different.Can't wait till 600.I would like ask,with this pre,do we need to add a power cord with sonic spectaculars.My tara labs air,has no sonic signature,just delivers good clean reasonibly fast power.So the pre is delivering the goods on its own,the way it should be, I suggest.Im interested in your thoughts as pc have come along way over recent years.Do I fix something,not broken,in that department.I do plan on holding onto this pre for along time,as its the best I've owned ,by a long way.My next best,imo was a ls 15.