Abstract: Prior art quadruplex head assemblies (equipped with metal heads) are detachable for purposes of refurbishment with ferrite heads. The concept of the invention is to mount corrective compensation circuits to each such refurbished quadruplex head assembly so that recordings by means of ferrite heads resemble recordings by metal heads. As a result, recordings produced by ferrite and metal heads are interchangeably playable on the same recorder without adjustment thereto. The compensation circuits are such that they self-disable during signal playback.