Echo
Units in PA Systems
What it is
Usually it is a 19" 1U box with knobs or buttons (and more often than
not some kind of menu display) on the front.
What it does
An
Echo 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).
How it works
There are three basic methods:
1.
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.
2.
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.
3.
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.
