Most effects processors are fairly simple to use; plug in an equaliser (for example), twiddle the controls, and listen to the output, and you pretty much know what you’re doing, and all you need is some experience behind you.
Compressors don’t fall into this category. Plug them in and listen. What’s it doing? Unless someone has told you, then you probably won’t know. Play with the controls. What do they do? Don’t know either. What do the indicators mean? Difficult to tell. It’s all a bit frustrating really…
( By Jezar at Dreampoint )
