As stereo LPs and FM broadcasts became well established in the 1960s, 100% mono compatibility became less important. The French broadcasting system ORTF – SCHOEPS' largest single customer for many years – developed a stereophonic recording method using two small-diaphragm cardioids 17 cm apart, angled outward at 110 degrees. Their experiments were made with SCHOEPS M 221 B and CM 51/9 microphones. The ORTF approach offered greater spaciousness than coincident microphone techniques, plus very even distribution of apparent sound sources across the stereo field. The SCHOEPS MSTC was the first microphone specifically designed for this recording method. It is a unitary, two-channel amplifier for capsules of the Colette series, with the required spacing and angles "preset"; it is most often used with a matched pair of MK 4 cardioid capsules. Its latest version (MSTC 7, 2021) uses the updated circuitry of the CMC 1 amplifier.