The manufacturer insists that the NAF will need a good 200 hours of break-in, but I'm elated enough, even at this very early stage, to report that this has been a very significant step toward the type of sound that I'm looking for. That said, there's still much tweaking to do and I'm sure that changes in associated equipment will be needed to realize the amp's full potential. If I was to choose a single element that stands out right now, I would have to say it's the frequency extremes. I expected that beautiful 300b midrange, but I wasn't quite prepared for such airy highs or the extended, tight base, especially since my current speakers are at the extreme low end of NAF's minimum efficiency recommendation.