I think the east river drive is a direct clone of the tube screamer circuit. I spent some time DIYing some pedals this winter, and while my understanding of them is rudimentary, I did find that many are the same circuit almost exactly. The tube screamers, the yellow Boss overdrive pedal, the East River, and numerous others. (Even the TS9 and TS808 are very similar and it’s easy to covert one into the other.)
There seem to be two main types, the tube screamers which cut bass and have a variable treble cut and boost the rest while adding some color, and the more transparent ones which go for a flatter boost with just a bit of color.
(That’s before you get into distortion where a lot of them seem to be based on the RAT or the Voodoo Labs Pedal, like the OCD is)
For me, I didn’t like the tube screamers for a long time. They seem to work best with single coils and I felt like they added gain but made the tone seem flatter. Where they really shine I think is when you put a tube screamer type after a pedal of the other type and run them both at once. Some people like the reverse arrangement too.
I have a Klon KTR which is the same as a Centaur, just the modern version, and I leave that on all the time and put the tube screamer after it as a further boost. They sound great!
Sorry for the long winded post. I need to type less and play the things more 😁