WA76 / WA-2A questions

WA-2A is a copy of the LA-2A
WA76 is a copy of the 1176
 
LA-2A provides a slower, smoother control over dynamics.
1176 provides a faster, more aggressive control over dynamics.
 
All depends on what you're after.
LA-2A is great for "reining-in" dynamics without the audio sounding squashed.
It's not great at eliminating quick peaks.
 
1176 is great if you want to make a track sound more aggressive... or if you want tight control over dynamics.
 
The combination of LA-2A and 1176 can cover most (broadband) dynamics processing needs.
 
 

Yes to all the above.  The WA2A has the stereo option built-in, but it is hardly a good candidate for the two buss since it is so slowwww.  Just right for vocals and many basses, but passing a whole mix through it, well, you'd have to think a lot about how you record and mix to make that happen.
 
I guess Zin Pro would modify an WA76 for stereo, but it would cost...
 
You can use either going into your interface (if you have an external pre for mic use or if the interface has inserts, which few do in these price conscious days) or from a previously recorded track.  In the latter case, you could put compression on or either or both or on every track.  You are just shunting it out and recording back in.  But one of the things that make either of those "classic" compressors stand out is the fact many, if not most tracks from the 60s/70s had a limited number of 1176s/LA2As available and they were usually only used on the lead tracks or important rhythm instruments.  So those elements really popped out - think how smoothly the vocal chorus in many pop/rock songs slide into the lead guitar - volume wise.  Some of that had to do w/ sending each of those tracks to the same comp during mix down since they only had the one available, so both instruments had the same feel and floated above the rhythm tracks with the same intensity .  I still have aux channel just that purpose.
 
The 1176 clones are probably more useful on more instruments, but the LA2A defines the sound of vocals on many, many popular tracks.  Once you get a grip on either of those comps, and how they effect the sound, you can use that live, during tracking, where it becomes like an instrument itself.  Each of those units has a "tone" that you've heard - an edge to the 1176 from saturation, while the LA2A adds a syrupy fullness to the sound from the tubes etc.  It can be quite a rush when you get that same tone from your home brewed tracks.