Other nuvistor applications included the Ampex MR-70, a studio tape recorder whose entire electronics section was based on nuvistors, as well as studio-grade microphones from that era, such as the AKG/Norelco C12a, which employed the 7586. It was also later found that, with minor circuit modification, the nuvistor made a sufficient replacement for the obsolete Telefunken VF14 tube, used in the Neumann U 47 studio microphone.[1] Tektronix also used nuvistors in several of its high end oscilloscopes of the 1960s,[2] before replacing them later with JFET transistors.