The Hitachi HD-66 is a model of headphones that was manufactured by Hitachi between 1973 and 1975 in Japan. It was offered at an approximate original price of 68 DM. Although specific technical specifications are not extensively documented, the HD-66 is part of a series that includes various audio equipment, such as amplifiers, tuners, receivers, and tape decks, highlighting its place within a broader audio ecosystem from Hitachi during that era. Other headphones in the same series include models HD-33 and HD-55.
