run through a volume control and to an amplifier stage. The amplifier feeds either an internal speaker or headphones. In a tuner component of an audio system (for example, a home high-fidelity system or a public address system in a building), the output of the detector is connected to a separate external system of amplifiers and speakers. The broadcast audio FM band ( in most countries) is around higher in frequency than the AM band and provides enough space for a bandwidth of This bandwidth is sufficient to transmit both stereo channels with almost the full hearing range. Sometimes, additional subcarriers are used for unrelated audio or data transmissions. The left and right audio signals must be combined into a single signal which is applied to the modulation input of the transmitter; this is done by the addition of an inaudible subcarrier signal to the FM broadcast signal. FM stereo allows left and right channels to be transmitted. The availability of FM stereo, a quieter VHF broadcast band, and better fidelity led to the specialization of FM broadcasting in music, tending to leave AM broadcasting with spoken-word material. AM/FM tuners Standalone audio stereo FM tuners are sought after for audiophile and TV/FM DX applications, especially those produced in the 1970s and early 1980s, when performance and manufacturing standards were among the highest. In many instances the tuner may be modified to improve performance. Electronics specialists and hobbyists buy, collect and restore vintage FM or AM/FM audio tuners on the secondary market. The restoration usually begins with replacing the electrolytic capacitors that may age over time. The tuner is outfitted with improved tolerance and better sounding upgraded parts. Prices have increased relative to the increasing demand for the older audio tuners. Those with the most value are the best sounding, most rare (collectible), the best DX capable (distance reception) and the known build quality of the component, as it left the factory. Most of the early tuner models were designed and manufactured to receive only the AM broadcast band. As FM became more popular, the limitations of AM became more apparent, and FM became the primary listening focus, especially for stereo and music broadcasting. The McIntosh MR78 is known as one of the first FM tuners precise enough to tune into a weaker station broadcast on the same frequency as another stronger signal. In Europe, where a second AM broadcast band