Taran, The SB2 was the one I replaced the op amp. It was not easy, beyond working with the SMD part, the PCB is of such poor quality that you might want to give it a pass.
For the SB3, I just jumped the output caps. I guess they are there for DC blocking but I only measured a very tiny DC offset. I see you are using a SR-45, as am I and it works fine. as well as my other tube gear.
Not saying that it wouldn't kill someone else set up...John