First off - there are 2 "types" of parametric EQs.
A "Full Parametric" (or simply "parametric") EQ found on the better consoles and on outboard units has 3 areas of control per each band (usually 3-4): sweepable frequency, "Q", boost/cut levels. The sweepable frequency pot allows you to select the frequency you wish to adjust. The boost/cut pot control is obvious. The Q setting controls how wide or narrow the boost/cut being applied will occur centered at the selected frequency. (Meaning, at higher Q settings, the affected frequency range will be very narrow - so if your selected frequency is 10K, you will pretty much affect only 10K, as opposed to the semi-parametric settings which will not only affect the 10K frequencies, but also much of the surrounding frequencies.)
"Semi-parametric" (often incorrectly referred to as simply "parametric") - has 2 controls: sweepable frequency, and boost/cut levels. This is typical in budget mixers and PortaStudios. Semi-parametrics are a bit of a compromise since, without the Q control to limit the scope of your adjustments, they have a tendency to affect too much of the surrounding frequencies of the one you're trying to work with. You just don't have the same level of control as with a full-parametric.
De-essing is not accomplished only thru EQ - it is a 2-step process involving a parametric EQ (set to boost the frequency you want to de-ess) and have it drive a compressor's sidechain to provide frequency-dependent dynamic cutting.
Using a PortaStudio's EQ may not have enough flexibility to give you the de-essing capability needed. If you decide to buy an outboard unit, make sure that for each frequency band (typically 3 or 4 bands of control), you get the Q control. There are a lot of budget Parametrics billed simply as Parametric EQ when in fact they are "Semi".
Hope this helps...
Bruce
