We've all heard it at one time or another - noise, crackle, weird moaning sounds. In many cases, these intermittent noises are happening at the patch bay. As the connections get dirty or the brass plugs begin oxydizing, they create resistive connections that cause anything from annoying noise to complete failure of a channel. This is the purpose of the "brush test" on the checklist. The brush test is simply taking your hand and brushing it against the jumpers at the patch bay, looking for intermittent connections. If a channel pops or sizzles, you've got a connection that's bad enough to cause you headaches if it decides to act up during a service.
Very important!!! This brush test needs to be done at a relatively low level. Master fader only needs to be up about 25 percent at most, just enough to hear the problem, and keep the monitors off. If you have the volume up too high you will be treated to some nasty loud sounds and you risk damaging the speakers. A noisy channel will be pretty obvious at the board - you will see the telltale lights flickering on the offending channel. Usually a wipedown with iso-alcohol on both sides of the patchcord will restore normal operation. In more stubborn cases, a little Flitz metal cleaner on the plug, followed by an alcohol wipedown, should do the trick.
Incidentally, if you have a patch cord plugged into the board socket, be aware that phantom power exists at the tip of the exposed plug. It's generally best to remove the cord altogether, clean it, then reinsert both ends. Make certain that the channel is muted and preferably that the master fader is down as well prior to removing or inserting patch cables.
Jim K.
No comments:
Post a Comment