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Echo and Delay Effects in Live Sound
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.
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.
Historically there have been three basic methods, of which only the third is now in widespread use:
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:
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.
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.
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.