Perception A|B is an updated version of the popular plugin used in audio mastering to make loudness-matched A/B comparisons—compare the same audio with and without processing. Perception A|B takes care of the level differences, latency differences—even with analog or digital outboard gear patched in to provide an objective way to compare two versions of the same audio.
This new version allows operation across all tracks in your mix session so you may ascertain the quality objectively of any processing you've made individually on any track and its affect within the context of the overall mix. Just being able to bypass entire chains with one click turns out to be amazingly powerful.
In my mixing work, I'm often asked to also master it to be ready for streaming. Perception A|B comes in handy to show to my clients what my mastering processing can do or cannot do—comparing before and after my stereo bus processing chain.
Perception A|B is a two-part plugin with the Pre instance first in the processing chain and the Post instance placed at the end of the chain. I have been using a pair of (analog) Pultec EQP500 equalizers followed by a Manley NuMu stereo compressor followed by DMG's Limitless limiter plugin.
I'm getting the hang of using Perception A|B and glad to have it for my mixing work. I can tell (and show my clients) who want it loud and do not necessarily hear what happens (big squashed compressions) overall to the sound. Now, I have a way to make it loud more objectively with greater precision and have a way to compare realistically.
Perception A|B sells for $149 MSRP and runs on AAX, AU, or VST systems on Mac OS 10.7 or later and Win XP SP3 or later 32/64-bit.