Mackie M1200/M1400 Owner's Manual

Also see for FR Series: HOOK-UP GUIDE Service manual Owner's manual

Mackie M1200/M1400 Owner's Manual Manual pdf 20 page image

20The AMP MODE switch determines the in-put signal routing within the M•1200/M•1400amplifier. Shipped from the factory, the switchis set to STEREO. This is correct for about 90%of the applications using an amp like this(hence the TYPICAL indicator near it). Butyou may be in the 10% bracket, requiring spe-cial input routing within the amp.AMP MODE should be configured beforeoperation — if you must change it during per-formance, turn down the GAIN controls asa precaution to protect the speakers from anyinadvertent pops or thumps.STEREO mode (separate left and rightinputs, separate left and right outputs) is thetypical setup for amplifying stereo signals.MONO mode (sometimes called Dual-Mono – one mono input, two mono outputs) isfor sending a mono signal to two differentspeaker sets, with separately-adjustable GAINcontrols.BRIDGE mode (sometimes calledBridged-Mono – one mono input, one monooutput) uses both sides of the amp to doublethe power to one speaker set. With two M•1200power amplifiers, each set to BRIDGE mode,you can deliver as much as 1200 watts peramplifier.If you set the AMP MODEswitch in MONO orBRIDGE, use the CHAN-NEL 1 inputs only — theCHANNEL 2 inputs go no-where in this case.Note: There is one exception to this rule. If youhave the OUTPUT APPLICATION switched toSUBWOOFER, the inputs to Channels 1 and 2are summed regardless of the AMP MODEsetting (see ). Also, BRIDGE mode re-quires special connections at the SPEAKEROUTPUTS .BRIDGEIn STEREO mode, the M•1200 PowerAmplifier can deliver 600 watts per side into2 ohms. If that’s not enough, you can use twoM•1200s, each in BRIDGE mode, and deliver1200 watts per amplifier into 4 ohms. TheM•1400 produces 630 watts per side into2 ohms in STEREO and 1260 watts into 4 ohmsin BRIDGE mode. Or, you can use one amp inBRIDGE mode to power a monaural system.Finally, BRIDGE mode is also popular forsubwoofer applications — but please seeSUBWOOFER for a special subwoofer surprise.To use all the M•1200/M•1400’s power todrive one speaker cabinet using BRIDGE mode,you’ll have to do four things:1. Turn off the power to the M•1200/M•1400.2. Set the AMP MODE switch to BRIDGE.3. Connect the positive side of the speakercable to the Channel 1 red (+) binding post.4. Connect the negative side of the speakercable to the Channel 2 red (+) binding post.5. (Okay, make that five things!) Use only theCHANNEL 1 INPUT (unless you’re usingthe SUBWOOFER OUTPUT APPLICATION).The CHANNEL 1 GAIN control adjusts theoutput level of the amplifier. The CHANNEL 2GAIN control has no effect.Once again: Before making connections toan amp or reconfiguring an amp’s routing, turnthe power off, make the changes, then turn thepower back on.OUTPUT APPLICATIONThe OUTPUT APPLICATION switch shouldbe configured before you turn on the amplifier.This switch allows you to choose between threedifferent configurations:LIMITER ON (TYPICAL). This is the normalconfiguration: full-bandwidth audio with pro-tective limiting (please see ).LIMITER OFF is also full bandwidth audio,but without protective limiting (please see ).SUBWOOFER mode, with built-in low-passfilter, no protective limiting (please see ).LIMITERThe LIMITER is not designed to alter yoursound — it’s just there to protect your speak-ers from clipping. Its effect is virtuallytransparent, meaning you probably won’t evennotice any audible difference. We recommendthat you leave it engaged (via OUTPUT APPLI-CATION ), hence the TYPICAL label below it.If you’re working at quiet levels all the time,or you’ve already placed a compressor/limiterin the signal path, or if you just hate compres-sion, you can leave the LIMITER out of thecircuit (via OUTPUT APPLICATION ).The LIMITER senses whenthe amp is about to beoverdriven and attenuatesthe overall level just enoughto keep the signal from clip-ping. Clipping occurs when the output voltageno longer linearly follows the input voltageand simply stops. This causes a sine wave to