Just having finished installing the 55 N+ upgrade today, I must say that there is a marked difference already from the start. Tonal balance might be a bit off initially, but there is definitely more detail, and the treble has become more tangible or bodily.
I can't wait for the thing to break in, but I think I'll do this by leaving the amp on 24 hours a day, playing music whenever I'm home.
There's absolutely no doubt in my mind that this is a serious upgrade from the Nirvana, which was already very good. It certainly moves this little beauty up to another league!
Good work, Hugh - and everyone who contributed to this upgrade
Cheers,
Jens