Operational amplifiers are the devices responsible for controlling the gain of our preamplifiers. These are fully hand-assembled and can come in two versions: TH (Through-Hole) and SMD (Surface Mounting Device). While they are electronically similar, some prefer one over the other. TH versions are believed to 'color' the signal because they are components that can have certain tolerances in their nominal values, while SMD versions are considered to be stable and uniform.

They serve as a direct replacement for API's 2520 operational amplifiers.