Mackie DFX 12 Owner's Manual - Page 22

Dimensions DFX•12 WEIGHT 10.0 lbs. (4.5 kg) 16.1" (410 mm) 4.1" (105 mm) 14.4" (365 mm) DFX•6 WEIGHT 8 lbs. (3.6 kg) 11.8" (300 mm) 14.4" (365 mm) AC Power Considerations The majority of AC outlets encountered in homes and clubs (in the U.S.) are served by a 240 VAC center-tapped service entrance transformer. This provides two phases of AC power on either side of the center tap, at 120 V 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). In order to minimize ground loops, the safety grounds for all the outlets should be connected to a common ("star") grounding point, and the distance between the outlets and the common grounding point should be as short as possible. When setting up for a show, oftentimes you are plugging into an AC power distribution system you know nothing about. You may even be faced with 2-wire outlets that are missing the third safety ground pin. It's a good idea to have a three-wire AC outlet tester in your toolbox so you can check the outlets yourself to make sure they are wired correctly. These testers will tell you if the polarity of the hot and neutral wires is reversed and if the safety ground is disconnected. Don't use an outlet if it is wired improperly! This is to protect yourself as well as your equipment. If you find that you must plug into a twowire outlet, you will need to use a two-wire to three-wire adapter (cheater plug). These come with a metal tab that you put underneath the center screw that holds the AC outlet faceplate in place. This center screw must be grounded. You can check it by connecting the adapter to the outlet and then plugging in your handy-dandy AC outlet tester. NEVER bypass the AC plug's ground pin. This is dangerous! 22