Note: When using the amplifier in BRIDGE mode, one or both SHORT LEDs may light under shorted or low impedance conditions. Regardless of whether one or both LEDs light, it’s an indication of a problem that requires further investigation.
TEMP STATUS
TEMP (short for temperature) is another feature designed to keep your mind at ease. Normally the COLD LED is lit, indicating that the M•1200/M•1400 is working normally. Under extreme conditions the amplifier may overheat. You may ask, “What kind of extreme conditions?”
Overheating problems are usually caused by one of the following situations: improper venti- lation, high ambient temperatures, overdriving the amplifier into clipping, driving the ampli- fier hard into low impedance loads, frayed or partially shorted speaker cables, or defective or internally shorted speakers.
The heaviest load the M•1200/M•1400 can tolerate is 2 ohms per channel (4 ohms in bridged mode). If you’ve got a set of speakers wired in parallel, be sure the load isn’t adding up to less than 2 ohms. Anything below 2 ohms can cause the SHORT 
LED to light and trig- ger the PROTECT mode.
Remember: As the load gets
“heavier,” its value in ohms
goes down. For instance, a
2-ohm speaker load is twice
as “heavy” as a
As the internal temperature of the amplifier rises, the fan kicks into high speed. This occurs at 60°C (140°F). More air moves through the
constant temperature gradient cooling tunnel to remove additional heat from the output transistors. However, if the internal tempera- ture of the amplifier should exceed 80°C
(176°F), the COLD LED turns off, the HOT LED turns on, and both PROTECT LEDs shine. The output of the amplifier is muted — at this point the amplifier is in Standby mode and remains there until the internal temperature cools off to a safe level (55°C or 131°F). When this occurs, the HOT LED and PROTECT LEDs turn off, the COLD LED turns on and normal operation resumes.
Be Aware: If the HOT LED
comes on frequently, some-
thing is overworking the
M•1200/M•1400 or it’s not properly ventilated. Look
at each of the “extreme conditions” described above and try to determine what is causing the amplifier to overheat. Refer to the “Trouble- shooting” section in Appendix A for more help.
What’s that? Why doesn’t the
fan just go fast all the time?
Well, if it did, you might actu-
ally hear it whirring during 
your quiet moments (there are quiet moments in your life, aren’t there?).
While this whirring would be of no concern in most
POWER
To make the amp operate, push the top half of the POWER switch. It clicks into place and a
(MONO BRIDGE)
1200 WATTS
4 OHM LOAD MIN.
600 WATTS CH
2 OHMS LOAD MIN.
120 VAC 50/60 Hz 1500 WATTS
CAUTION |
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RISK OF ELECTRIC SHOCK | NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL. |
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REPLACE WITH THE SAME TYPE FUSE AND RATING. |
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| CONCEIVED, DESIGNED, AND MANUFACTURED | |
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| BY MACKIE DESIGNS INC • WOODINVILLE • WA | ||||
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| CH | 98072 • USA • MADE IN USA • PATENTS PENDING | ||||
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SPEAKER OUTPUTS 
M•1200 Rear Panel
14
