The CA-2A is one of the most useful comps on the PC. The only 3rd party PC comp is the FET, as part of the Softube bundle. So you are basically stuck w/ the CA-2A, 4K and the 76. The 4K is a buss compressor, and I use it all over my busses - guitar, drums etc. It really shines there. The 76 emulates the 1176 FET comp (softube FET is modeled on the same hardware). I use it a lot on tracks and it works great for stabilizing levels. On lead stuff, esp. vocals, I'll use it and the CA-2A, which is modeled on the LA-2A optical comp. The CA has more "tone" than the FET models, or maybe it is because I have the Warm 76 here at home and none of the soft comps deliver the tone I can ladle on in the hardware. The CA also has a gentler touch on dynamics.
I find all 3 valuable - the 4K ssl comp is perfect on the guitar buss. Or I've found it so. I'd suggest getting the CA - tho calling it the best is probably not right. It is a great tool and does some things the other 2 Cake PC comps don't. But running your guitar (or whatever instrument) through a nice analog comp (or channel strip) really helps the digital sound. Not only does it do tone (if you get a Warm or Neve etc.), it also helps stabilize your signal going in. You don't have to squash it, but just do a little shaping going in. Then the PC comps can fine tune the tame dynamics and will sound their best doing it.
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