The Echoplex was a delay effect that used magnetic tapes, first made in 1959. Designed by Mike Battle, the Echoplex works by recording sound on a magnetic tape, which is then played back — the tape speed, in combination with the distance between the record and playback heads determines the delay time, while a feedback variable (where the delayed sound is fed back to into itself) creates multiple echo repeats.
In 1961, an Echoplex with tube preamplification and a moving head to allow for variable delay times was introduced. In the late 1960s, the solid-state amplified EP-3 was released. Some guitarists, such as Jimmy Page and David Gilmour, loved the sound of the Echoplex preamps so much, they put them in the signal chain even when they weren’t used as delay effects. Echoplexes are in very high demand in the used market, and scores of delay pedals and effects attempt to capture the magic of the Echoplex preamp and tape delay.