Mackie M800 INPUT WIRING, OUTPUT WIRING, Load, Gauge of, Impedance, Wire, AC Power Distribution, Wire Length

AC Power Distribution

The majority of AC outlets

encountered in homes and

clubs are served by a 240VAC

center-tapped service entrance transformer. This

provides two phases of AC power on either side of the center tap at 120V each.

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.

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 are used).

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 dis- connected. 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 two- wire 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 should be grounded. You can check it by connecting the adapter to the outlet and then plugging in your AC outlet tester.

HIGH VOLTAGE POWER LINE

	120V
PRIMARY	240V	SECONDARY
WINDING		WINDING
	120V
TRANSFORMER	EARTH
	GROUND
	(NEUTRAL)

240V Center-Tapped Secondary

INPUT WIRING

Use a high-quality 3-conductor shielded cable to connect the signal between the signal source (mixing console, equalizer, etc.) and the balanced inputs to the amplifier. If you’re using the unbalanced inputs, use a high-quality 2-conductor shielded cable. Your Mackie Dealer can recommend a suitable cable for your application.

OUTPUT WIRING

Use heavy gauge, stranded wire for connecting speakers to the M•800 amplifier’s SPEAKER OUTPUT terminals. As the distance between the amplifier and the speakers in- creases, the thickness of the wire should also increase. Speaker wire has resistance, and when electricity passes through a resistor, power is lost. The thicker the wire, the less resistance it offers, and the more power actually gets to the speakers.

The thickness of wire is rated in gauges. Use the chart below to determine the correct gauge of wire to use according to the distance between the speakers and the amplifier, and the impedance of the load the amplifier is driv- ing. This ensures that the power lost across the speaker wire is less than 0.5 dB.

	Load	Gauge of
Wire Length	Impedance	Wire
Up to 25 ft.	2Ω	14 gauge
	4Ω	16 gauge
	8Ω	18 gauge
Up to 40 ft.	2Ω	12 gauge
	4Ω	14 gauge
	8Ω	18 gauge
Up to 60 ft.	2Ω	10 gauge
	4Ω	12 gauge
	8Ω	16 gauge
Up to 100 ft.	2Ω	8 gauge
	4Ω	10 gauge
	8Ω	14 gauge
Up to 150 ft.	2Ω	6 gauge
	4Ω	8 gauge
	8Ω	12 gauge
Up to 250 ft.	2Ω	4 gauge
	4Ω	6 gauge
	8Ω	10 gauge

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