Echo (Delay)

Echo and Delay Effects in Live Sound

What it is

Usually an echo or delay unit will be housed in a 19″ 1U box with knobs or buttons (and more often than not some kind of menu display) on the front. However, the effects may also be found in dedicated effects pedals (primarily for guitars), and mixer Effects sections. Delay - as a function, not as an ‘effect’ - can also be found in system controllers.

What it does

An Echo (also known as Delay) unit creates a copy of the original signal and after an interval (usually selectable within a limited range) replays it one or more times. It simulates the way a sound can be reflected by a single acoustically reflective surface (a cliff, for example).

Although it is often also called Delay, in practice the effect is invariably Echo: the delayed sound is mixed with the original sound, producing one or more discreet repeats. However, while delaying the whole signal isn't used as an effect, a delay function is quite commonly included in crossovers and system controllers to time-align the sound from separate loudspeakers or loudspeaker drivers.

How it works

Historically there have been three basic methods, of which only the third is now in widespread use:

Tape. A record head records the original signal onto a continuous loop of tape. At a distance from the record head, one or more replay heads replay the signal. Single or multiple echoes are usually available, and delay times can be altered either by moving or changing the replay head(s), or changing the tape speed.
Electronic. A copy of the original signal feeds a ‘bucket brigade’ delay line, from which one or more delayed copies of the original signal can be replayed.
Digital. A digital copy of the original signal is created, and replayed one or more times.

How do you use it?

If all else fails, read the manual!

For connection details, refer to the unit's manual and/or to the section on Mixers.

Generally there will be controls to determine:

Interval. The length of time between the original sound and the first and subsequent echoes.
Count. The number of echoes.
Level. How loud the echo is compared to the original sound.
Feedback. Whether the echoes are themselves echoed, and in what proportion.

A common technique is to time the echoes to match the beat of a song. Some units have a Tap button, so that you can set the interval by tapping the button (rather than by entering a value or scrolling through values). For live shows - where the tempo of the same song may vary from one night to another - this can be useful.

Do you need one?

If using echoes is a feature of one or more songs in the production, then you need an echo unit (most digital reverb units can also produce echo effects). Otherwise, you probably don't.

What sort do you need?

The original WEM Copicat is still around, but tape-based machines can be troublesome, and at best will only require careful handling and regular maintenance. Even very low-budget digital multi-effects units usually include some kind of echo effect, and will also be more versatile and sound better.

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