Here's a frequency response plot for the Alesis M-EQ 230 graphic eq bypassed (black), engaged with filters zeroed (red), +12dB @ 1kHz, -12dB @ 1kHz.
Notice how the whole band tilts and rolls off toward the LF, and how the 1kHz slider controls a filter that's not exactly centered on 1kHz. On the positive side, the slider detents did seem to defeat each filter as the zeroed response was smooth.
For a budget eq the Rane Mojo MQ302 is pretty decent. This one, however, seems to have issues. It is an earlier version of the eq.
Next is a Tascam PE-40 4-channel 4-band parametric eq. Shown is the lowest of the four frequency bands fully boosted, its frequency centered and the Q at minimum, center and maximum. There's a little wavy spot in the response of the minimum and normal Q settings but not in the maximum Q setting.
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I have a PE-40 that's great for destroying things once in a whil
I have a PE-40 that's great for destroying things once in a while...lots of fun to use but there's a lot of hiss...it's noisey...but cool for things where that doesn't matter much, like electric guitar or drums.
In bypass mode it's great for adding analog thickness to something that's cold, sterile or just lacks character in the bottom end. The PE-40 alone weighs more than everything else in the rack put together, LOL.