GillyDJ wrote:Thanks Tim
I read Khazul's post again and it makes more sense this time except for the second para which I don't fully understand. But thanks Khazul.
Create a rack with two chains on a audio track with some audio in it.
Chain 1 - stick a utility and enable phase inverts.
Chain 2 - empty.
You will hear nothing - because the phase invert changes the signal value such that -ve become +ve and visa versa - add N to -N and the result is zero. That is the basis of subtraction of one signal from another inside a DAW and its really useful for some interesting signal processing.
Now stick an EQ8 in chain 1, disable all the Eqs apart from 1, set that to a notch, and do a cut. - you have made yourself a very transparent and potentially very steep band isolator.
The band above and below the notch are the same as the audio in the otehr chain, so they cancel out. Whats removed in the notch in only partially cancelling - depending on deoth/width of the notch - leaving you with the isolated band. If you were to stick compressor in the isolated band chain, tune it for vocal esses you will ave made yourself a very transparent and highly selective de-esser. With the compresor in place, tune it down to out of control sub-bass, and you can now compress it in isolation without effecting other frequencies etc - basically lots of cool shit you can do with phase inversion to setup subtraction in racks with an EQ8 in normal mode.
Because filters cause a phase inversion, then you may or may need the utility dong the phase inversion- for eg - one stage of low cut or high cut (in EQ8) needs it, but two stages doesnt (as they reverse the phase twice).
You can take this further - making your own transparent cross over stages etc, or simpler things like making you own stereo->mid side decoders and encoders - really handy for mid/side mic recording.
Caveat - Not running live at the mo - so this is from memory of EQ8 - might be the other way around on the phase inversions