Exactly what i was thinking.Plug ins only apply to post recording.If you want to compress the signal beforehand you'll need a hardware compressor like a rackmout or an effects processor that includes a compressor.
Actually some DAWs do allow you to record through an input bus so the tracks are recorded with effects. This can be usefull if you know what you want in tracking and don't want to tie up the system with a bunch of CPU hungry VSTs during mixing. It's akin to tracking with effects althoug if you are using a compressor to avoid cliping the converters it won't work because all of the effects happen post conversion but pre track recording
In the lower price ranges just about any plug in will kick the ass of the budget outboard compressor, unless it has a specific mojo for your specific track.
Not necessarily
FMRs RNC, RNLA (can be had for under $100) and
ART PRO VLA II (got one for $158) ,especially retubed, are examples of very nice tracking compressors that cost less than many plugins (even if you buy new and not used as I did)
Doing this means you have the opportunity to audition a number of different units/plugs to find one that suits the performance and production. To do this on the way in would need a really patient singer!
Or an engineer who really knows what his gear does
compressing on the way in is really more of a choice than a necessity in 24 bit recording systems. but if you know you're going to compress anyway, you know what sound you want and what hardware compressor will give you that sound and are confident that you can set the compressor right then why not.
one might even argue that if you don't know which type of compressor to use on the vocal even after the fact and have to audition a bunch, you're not ready to record because you haven't got a clear vision of how the track is going to sound. Either that or you haven't got a clear idea of what your compressors do.
While this is a very good way of finding out/Learning what your compressors do by running the same signal through many different ones, it really shouldn't be something you have to do on every track every time. Once you know your equipment/plugs, it should be fairly obvious which is right for the job IMO.
As with all things recording, there are no hard and fast rules and using tracking compressors is not a no no at all. Using any compressor at any stage during or post tracking without knowing why, How to set it and what it actually does is more than likely a foolish waste of time however.