I am impressed by the “knob in a knob” design of the 550 (and others). It saves space, and it also does what is impossible to reproduce on a screen: it utilizes 3-D space. We can move our hand up and down, back and forth, AND father and closer. UI designers, take note!
The choice of frequencies always seemed mathematical rather than natural on these, although they are so wide it doesn’t really matter. The overlapping ones (ie. 5k on MF and HF) are fun to boost and attenuate at the same time. Try it and see what I mean. (I guess that qualifies as a “hint”.)
Check out the 5Hz spike. This occurs in a couple other UAD plugins. (See the Curve Bender) Is it being modeled from the hardware or some software error, *DC offset maybe or what? Does anyone know, feel free to leave a comment?
*DC offset = my likely contender.