, good input impedance (5 MΩ typ.). The first RC4558 monolithic dual opamp was developed by Raytheon Semiconductors in 1974. Plus a socket so if you build one you can swap out easily, there are other options but this is the classic.
This product would be best suited for individuals looking to repair or maintain vintage tube amplifiers, specifically those incorporating the JRC 4558 socket and Opamp chip.
