They're complete different mics. I've tried a couple of NT1s and they can vary. In many cases, your typical Chinese condenser with a somewhat hyped high end and a sound bordering on harsh. (There were at least two designs of the NT1 in its production life...)
I tried one NT1-a, and though it still has that high-end bump, is much milder than I expected. It also is very quiet. Difference between that and my Marshall and Samson is night and day, and it has a slight edge over my CAD M179 in noise...
There are 3 different ones... the original NT1, the some what newer NT1, and the newest NT1A and they're all different sounding from each out. The original NT1's are the ones many people like the best.
