Mackie SRM350 Owner's Manual - Page 12

THERMAL CONSIDERATIONS AC POWER CONSIDERATIONS The amplifiers inside the SRM350 are convection cooled by a large heatsink. For efficient cooling, it is important to allow at least six inches of free space behind the SRM350. If the ambient temperature in the room is high, it could cause the amplifiers to overheat. In this case, you should try aiming a fan at the heatsink to increase the air flow through the fins. During a performance, don't have it cranked so high that the rear panel LIMIT LED is blinking frequently or lighting continuously. You should turn down the LEVEL control a notch or two to avoid overheating the amplifiers or your neighbors. If the amplifiers begin to overheat, the Active Protection Management System gently reduces the input signal level until the amplifiers have cooled down to a safe operating temperature. Be sure the SRM350 is plugged into an outlet that is able to supply the correct voltage specified for your model. If the voltage should drop below 97% of the specified line voltage, the built-in amplifiers will no longer be able to supply rated power. (They will continue to operate down to 75% of the rated line voltage, but won't reach full power, resulting in lower headroom.) Under maximum SPL conditions, where musical peaks are clipping, the SRM350 120V model draws 2.5 amps on average (1.3 amps for the 230V model). Under normal conditions, the current draw is below 1 amp. We recommend that a stiff (robust) supply of AC power be used because the amplifiers place high current demands on the AC line. The more power that is available on the line, the louder the speakers will play and the more peak output power will be available for cleaner, punchier bass. A suspected problem of "poor bass performance" is often caused by a weak AC supply to the amplifiers. AC Power Distribution A 240VAC center-tapped service entrance transformer serves the majority of AC outlets encountered in homes and clubs (in the U.S.). This provides two phases of AC power on either side of the center tap, at 120V each. If lighting is used in a show, it is preferable to power the lights from one leg of the service, and power the audio equipment from the other leg. This will help minimize noise from the lights coupling into the audio (particularly if SCRs, or light-dimmer switches, are used). HIGH VOLTAGE POWER LINE PRIMARY WINDING 120V 240V SECONDARY WINDING 120V TRANSFORMER 240V CENTER-TAPPED SECONDARY EARTH GROUND (NEUTRAL) 12