I used to think that an opamp was pretty much an opamp, but while working with the PG, I developed a custom, opamp switching circuit, and parcitipated in a lot of listening tests.
I was actually expecting my findings to correspond to my beliefs, but it turns out, an opamp is not just an opamp. Not to me anyways.
One of the discrete opamps being tested kept coming up as "exciting and vibrant, but just too much for a mastering EQ somehow".
I had to build something around it and thought a Bax Style EQ would be perfect for a simple circuit with some great ingredients, and also a perfect companion to the PG
Aside from the choice of opamp, the basic Bax design was a pretty straight forward implementation, but I decided to go for precision in the controls, frequency swtiching on matched caps, and decided to use the Blore Edwards PZ series switches for this one as well.
I think of it as the best possible "tomato, basil and mozarella" combination for the rack.