Since there isn't a separate side chain input, the pre-emphasis does a high freq boost with an equal high freq cut at the compressor output.
This affects the compression by changing what the detector sees.
Richard
right. i understand that much but how does that affect the overall guitar tone?
I need to experiment with how it is implemented in the AxeFx.
I imagine if you crank the emphasis you can get the compressor to kick in on higher frequencies with lower thresholds. IOW, you can set the amount of compression overall lower but still get the high notes to squash.
From the old Ross pedals, the emphasis / de-emphasis also affects the note attacks too. Gives a distinct roundness to them that a lot of folks find desirable.
Richard
I think this parameter has been introduced as the result of a recent thread where Radley asked for it.
It only has a very subtle impact in my experience so far.