Juice Goose Spotlight- What, Why and How: Power Sequencing

WHAT?

Power Sequencing uses one or more AC power relay modules to control the turn-on and turn-off of equipment in an audio-video system. Turning them on and off in the right sequence is important.   

WHY?

Audio signal source and processing equipment, such as mixing consoles and the like, produces a strong “square wave’ signal output when first turned on and when turned off. If this signal is amplified and channeled to a speaker the result is an audible “thump” which is annoying to the listener and potentially damaging to the speakers. The “thump” is actually a sudden and extreme movement of the speaker driver. Perhaps initially, but certainly after repeated occurrences, this extreme movement can damage the speaker driver and cone. Repairs can be expensive, especially if the speakers are difficult to reach.

This problem is eliminated if the amplifiers are turned on after the other equipment and turned off before them. The use of AC power sequencing equipment allows this process to take place automatically, without reliance on operating personnel and without the need to walk from the audio mixing console to the amplifiers and back each time the system is turned on or off.  Other advantages may include reducing access to audio equipment by requiring a key or numeric code and a single point of control for an AV system. 

HOW?

Three main factors determine the best equipment for power sequencing:

a) the number of circuits being controlled,

b) the location of the circuits, 

c) the amperage or current capacity of individual circuits.

Usually, one sequencer will be located at the FOH location along with an activation key or switch. Other sequenced power modules may be in an amplifier rack or located near powered line arrays or sub woofers. Those remote units may control one or more AC power circuits. When connected with signal lines, each power module will turn on in a prescribed sequence and turn off in the reverse order, eliminating the need for manual operation and the risk of equipment damage.