Ok, I've been trying to do some research on external a/d d/a converters (i.e. lucid 9624). Could someone please explain to me the use of an external converter other than simply "it takes the conversion out of the computer which is a noisy environment". At the time I'm only recording vocals. Is there a need? I understand a good a/d will convert the signal cleaner than a cheap-o, but what about a d/a what purpose does this serve or could serve while tracking and post production?