I don't know the nt-1a but have 2 nt-1's, chosen from a lot of ten (from among the first shipments to LA years ago). Most of them sound lifeless to me. I managed to find two that have a rich bottom and some "glisten." I've heard a few mic comparisons using nt-1's and those mics don't sound at all like mine, so there is wide variation.
Pros - very low noise, versatile with various instruments, CLARITY, well built, if you have a choice look for the ones with higher output.
Cons - Some (most?) sound blah, inconsistent capsules and output levels, cardioid pattern is a little wide.
I really don't find this to be a very useful vocal mic unless the singer has a rather dark sound. It's pretty good for percussion, live ensemble recording, guitars and mellow sounding instruments. Don't think I would use it on a violin or anything screechy.