A leveler is just another name for a comp. The PCA2 is a leveling amp. Usually these are based on the LA2A, hense the T for Tube (not texas or nor tennesse). So there is a slower attack time involved and some saturation.
There is no reason not to use (tho I haven't) for mastering, esp. combined w/ something that will grab the attack and transits hard. Like an 1176. That is a typical vocal comp chain. Limiter to tame the peaks and an LA2A to keep the level raised and evener (did I just invent a word?).
Theoritically, that should work too on an entire mix. For me, I use a komit conmpressor (analog stereo), which is a smooth ssl comp followed by a diode limiter. Great for rock/industial because you can drive the limiter to saturation - and it is a hard limiter. It will put hair on the chest of your song. One has to be careful with quieter songs, tho.
Same kind of thing w/ the 1176/la2a chain, tho no tube. And the ssl ain't as grabby.
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