I'm talking about settings you can use on your friendly neighborhood RComp or compressor of choice, that closely emulates the behavior of an LA2A / 1176 / SSL / etc.

I recall reading that a good setting to emulate the SSL comp using RComp is:

Attack - 2.00
Release - 199
Ratio - 2.00
Manual, Electro, Warm

Also here's a setting to emulate the Alan Smart C2 with the Sonalksis SV-315. I took this from a post by Treborflowl, hope he doesn't mind:

Attack 5-10ms
Release 150-250ms (sync to the 1/8th note of the song)
Crush 15-20%
Knee 18dB (sometimes use about 12dB for a tougher sound)
Filter type 3rd from left
Hold - off
Limiter - off
Gain make-up added at output NOT on the graph with the little triangle (+3dB)
Detector type I
Auto Gain - off
Ratio 2:1
Threshold set to reduce by about 2-3 dB on the loudest bits - or more to taste.

I'd also like RComp settings to emulate an innerTUBE Atomic Squeezebox ... anyone?

Not to be a jerk with providing an answer I'm sure the original poster wasn't looking for - but:
while I've been an advocate of doing work "in the box" since 1994 - honestly - if we're talking about broadband compression across the entire mix - then I've yet to hear a digital tool, emulating or not, even to this date, that sounds to my ear as satisfying as the best analog compressors. While in mixing I can see the tremendous value of plugins (as it allows to have much better quality than mediocre "budget" analog processors, while also allowing a much greater ease in signal routing and having a large number of processors available all at different recallable settings for each and every track) - for mastering for an album destined for commercial release I simply can not see why you would want to make a compromise in regards to the quality of processors used across the entire mix. Of course as always - YMMV!

Best regards,
Steve Berson

maybe I posted this in the wrong forum as I wasn't specifically talking about master bus compression. Vocals, drums, etc.

I have heard people say "I got xxx compressor to sound pretty close to xxx compressor." If you're one of those people, share your settings with us.

If you're completely against the idea that any software compressor could remotely resemble behavior of a hardware compressor...then don't even bother replying.

yes, you did.

this should be moved out of mastering - into low end

Why low end? He's asking emulation of "LA2A / 1176 / SSL / etc". The low end guys sure will have one or more of those pieces ...

"Low end" because he's talking about plug-ins? You're stereotyping plug-ins. This is nothing but discrimination.

The UA plugins compress in a similar way to the hardware counterparts. The 1176 doesn't sound nearly as cool with the needle pinned as the real thing though. Neither does the hardware reissue either. The Voxengo Marquis comp and Sonalksis can do the SSL thing kind of. I haven't tried the waves or URS ones yet.