The discrete amps in the ITI are one of the reasons for the hi freq sound quality but just comparing it to a serial chain eq bands, (feeding one into the next), have ability to do drastic surgical eq but have had a metallic top end to me where maybe there running out of slew rate.
I dunno man, you're moving the goal posts again. I don't think there is one factor that makes a good design work, everything counts. George and Burgess have long held that the speed of their opamps was a factor in the sound of the units, as far as I can tell it just made them more vulnerable to failure.
I'll leave it to the better minds here but I don't see how massively over speccing slew rate can bring anything to the table.
It could be other reasons as you suggest. In Massenbergs own description maybe from the original AES paper , he describes that he also played with state variable filters in series and did not like the sound as well as the design he used in the ITI that be came a parallel feedback circuit as you describe. Later that became sontec and then Massenburg I’ve like topend better from parallel feedback eq’s. IMO.
That said your the mastering engineer. Do you use eq in a parallel channel hookup? Or with a blend? It was the original question from boji.
There's a lot of lore around the original ITI EQ, I wouldn't pay too much attention if I was looking for real engineering knowledge.
I use two analog EQs daily, one a heavily modified Porter with SVF in one feedback loop, the other a design by my friend Dave Collins with several filters in series. Both sound great.
I guess I'm fighting the idea that we should categorize EQs into serial or parallel, or that it in some way tells us something useful. It seems to be something that started with plug ins.