Echo Chamber - Electronic Echo Chambers and Echo Machines

Electronic Echo Chambers and Echo Machines

In the 1950s and 1960s, the development of magnetic audio tape technology made it possible to duplicate physical echo and reverberation effects entirely electronically. The Watkins Copicat, designed and built by renowned British electronics engineer Charlie Watkins in the late 1950s, is typical of this kind of electronic delay device.

Tape echo units use an endless loop of magnetic tape, which is drawn across a series of recording and playback heads. When a signal from a voice or instrument is fed into the machine, it records the signal onto the tape loop as it passed over the record head. As the tape travels on, the newly recorded signal is then picked up by a series of playback heads mounted in line with the record head. These play the sound back as the signal passes over each head in turn, creating the classic rippling or cascading echoes that are typical of tape echo units.

The number of playback heads determines the number of repeats and the physical distance between each playback head determines the ratio of delay between each repeat of the sound (usually some fraction of a second). The actual length of the delay between each repeat can be varied by a pitch control that alters the speed at which the tape loop moves across the heads.

Typically, the playback heads of tape echo machines are also connected to controls that allow the user to determine the volume of each echo, relative to the original signal. Another control (sometimes called "regeneration") allows the signal from the playback heads to be fed back into and variably mixed with the original input signal, creating a very distinctive "feedback" effect that adds more and more noise to the loop with each repeat. If fully activated, this control will ultimately produce a continuous feedback loop of pure noise. Roland manufactured various models of magnetic tape echo and reverb sound effect machines from 1973 until the introduction of digital sound effect machines.

Tape echo that has few repeats and a very short delay between each repeat is often referred to as "slapback" echo. This distinctive sound is one of the key sonic characteristics of 1950s rock and roll and rockabilly, and can be heard on the classic mid-50s Sun Records recordings by Elvis Presley and others.