A handy overview of common problems that can crop up with church sound systems and easy ways to address them.
February 20, 2012, by Bruce Bartlett
Following is a list of some common sound problems and several ways to solve them.
At least a few of these might seem obvious, but we’ve all made simple mistakes like not flipping a switch.
If the advice given here doesn’t work, determine which device is at fault, then obtain help from tech support at the manufacturer or contact a qualified audio professional.
—Be sure everything is plugged into AC power and turned on. (Sorry – had to mention it!)
—Be sure that all cables are connected to their proper equipment inputs and outputs.
—Put fresh batteries in wireless microphones.
—Replace broken cables.
—Check for signal presence in each component by looking at the meters or indicator lights. Look for trouble in the first component in the chain without a signal, or in its input cables.
—Check all switch positions. Is a mic/line switch set to “line” when it should be set to “mic?” Is a fader down that should be up? Is a microphone not assigned to the proper channels or groups? Are any mute or solo buttons pressed? Is the input trim turned all the way down? Is a wireless microphone turned off? Is phantom power turned on for condenser mics?
—Use a headphone amplifier and headphones to troubleshoot the system one component at a time, from output to input.
—If distortion can be heard on every sound source, make sure that the power amplifier is not turned up so high that it is clipping. There could be the need for more amplifier power. Doubling the power increases the SPL by 3 dB.
—Make sure that the mixer meters do not reach above 0 (except occasionally).
—If the mixer output is balanced, +4 dBu, but the device it is feeding is unbalanced, -10 dBV build and install a 12 dB pad between them. Or set the +4/-10 switches accordingly.
—A stray wire in a connector might be causing a short circuit which can create distortion. Check inside each connector for stray wires and cut them off.
—Clean connectors with Caig Lab DeoxIT.
—There could be too many loudspeakers connected to the power amplifier, so that the load impedance is too low for the amp. Remove some speakers and see whether the distortion stops. If so, use another power amplifier for the additional loudspeakers.
—If only one microphone is distorting, locate its input trim (gain or atten) control on the mixer. Turn the control down just to the point where the distortion stops, then a bit more to allow some headroom.
—If the input trim is set correctly and you still hear distortion, switch in the pad in the mic, or substitute another microphone. Also, replace the batteries in battery-powered microphones.
—There might not have enough phantom voltage for a condenser mic. Most of these mics need 18 volts or more. If several condenser mics are plugged in, the phantom voltage might drop too low. Consider using an external phantom supply.
—Be sure that mixer meters are reaching 0 on the loudest parts of the program. If this is too loud, turn down the power amplifier, not the mixer.
—Check that the input gain or trim for each microphone is not turned down too far.
—Check that the mixer master faders and submaster faders (if any) are at or near design center.
—Replace the batteries in battery-powered microphones and transmitters.
—If a pot crackles when turned, try to clean it by rotating it rapidly. Eventually it should be cleaned internally by a service technician. Also try cleaning and lubricating products from www.caig.com.
—If a mic cable crackles when moved, replace it with a new cable or a higher-quality cable. Also check the solder connections inside each cable connector.