This is the Raytheon RC4558D. While it doesn't have a flashy or peaky sound, it produces a natural tone that can be used even when distorted on its own. This is from the same lot as the one used in the Leqtique MA:Limited. The MAR uses a socket, so it can be easily replaced. - Model: RC4558D - Pin Count: 8 pins - Type: Op-amp - Package: DIP Thank you for viewing.