Check this out. I have one DVD/CDR and one CDRW. I use the DVD/CDR as my main drive because it's the faster (40x) of the two. The audio out (4-pin connector) from the CDR is plugged into my soundcard.
Just last week, I put an audio CD into my CDRW by mistake...wasn't really looking at what I was doing. As it started to spin-up, I said to myself; "self, that was dumb, you'll prolly get an error message on screen and no sound!" Much to my surprise, it started playing just fine. I didn't know it, but I guess you don't need the 4-pin connector plugged in to get sound off a CDR drive. I don't know the tech explanation for this, but I can tell you that I couldn't tell the diff in sound B/T the two drives. Thought I'd throw this one in the mix.