Mackie FRS-2800 Owner's Manual - Page 10

FRS SERIES AMPLIFIERS 10. AMP MODE This switch determines the input signal routing within the amplifier. For most applications, you will use the stereo setting. However, some applications might be better suited for using either the mono or the bridge setting. Stereo: This is the normal position used when amplifying stereo signals. This mode accepts separate left and right inputs (1 and 2), and routes them to the channel 1 and channel 2 outputs. Each channel's level control adjusts the gain for its own channel, and each channel is independent. Mono: This mode (also known as dual-mono) is used when you want to send a mono signal to both outputs. It accepts a single input (input 1), and routes it to both the channel 1 and channel 2 amplifiers. Each channel's level control adjusts the gain for its own channel. Bridge: This mode (also known as bridged-mono) accepts a single input (input 1), and uses both amplifier outputs to power one speaker. Use the channel 1 level control to adjust the gain (turn the channel 2 level control all the way down). The hookup diagram at the bottom of page 6 shows how to connect a speaker in bridged mono. WARNING: In bridged mode, both connections to your speaker are live; that is, neither is grounded through the chassis (because the black binding posts are not used). the output voltage no longer linearly follows the input voltage. As the amplifier output voltage increases, it will eventually run into the internal DC power supplies and start to flatten out. The flat tops represent a DC voltage reaching your speakers, which interrupts the natural movement of the speaker's voice coil. High frequency harmonics are also produced which can play havoc with your tweeters. Square waves sound awful, and could possibly damage your speakers and/or your reputation. Speakers are designed to handle good clean continuous signals, but give them a clipped signal and even high-power speakers can be damaged. For example, a 100 watt amplifier that is clipping, can damage speakers that are rated at 400 watts. The limiter is especially handy when you're working with loud output levels. Having the signal spikes (kick drum, for instance) attenuated a bit can actually increase the apparent loudness of the overall mix without diminishing the "power" behind the spikes. It is also a useful protection device for those unexpected moments, such as the lead singer actually hitting the right note, a mike stand or the drummer falling over, dropping the tone arm, or an attack of killer feedback. With the limiter engaged, you can still overdrive the amplifier into clipping and cause distortion. It just takes a stronger signal to do it. So even with the limiter turned on, you must pay attention to the OL LEDs. 11. CLIP LIMIT When engaged, this switch protects your loudspeakers from the effects of clipping. It is designed to be virtually transparent, meaning you probably won't even notice any audible difference when the switch is turned on. We recommend that you leave this switch on at all times. However, if you are working at quiet levels, or you have already placed a compressor/limiter in the signal path, you can leave this switch off. The limiter senses when the amplifier is about to be overdriven and attenuates the overall level just enough to keep the signal from clipping. Clipping occurs when 12. SUBSONIC FILTER Turn this switch on to engage a low-frequency cutoff (high-pass) filter at 30 Hz. The frequency range below 30 Hz is attenuated. The amplifiers can amplify signals below 20 Hz, but most speakers can't reproduce frequencies that low. By engaging the subsonic filter, you allow the amplifier to power only the frequencies you can hear. In addition, this filter can reduce low-frequency stage noise (footsteps) and accidental microphone pops that could damage a loudspeaker. Leave this off if your amplifier is powering a subwoofer, or if your speakers can reproduce low frequencies such as the kick drum range. FAST RECOVERY POWER AMPLIFIER CHANNEL 2 BRIDGED CHANNEL 1 : WARNING TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE. DO NOT REMOVE COVER. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL. : AVIS RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR THIS DEVICE COMPLIES WITH PART 15 OF THE FCC RULES FOR THE U.S. AND ICES-003, FOR CANADA. OPERATION IS SUBJECT TO THE FOLLOWING TWO CONDITIONS: (1) THIS DEVICE MAY NOT CAUSE HARMFUL INTERFERENCE, AND (2) THIS DEVICE MUST ACCEPT ANY INTERFERENCE RECEIVED, INCLUDING INTERFERENCE THAT MAY CAUSE UNDESIRED OPERATION. DESIGNED BY MACKOIDS IN WOODINVILLE, WA, USA • MANUFACTURED IN CHINA FABRIQUE EN CHINE • COPYRIGHT ©2007 "MACKIE", AND THE RUNNING MAN FIGURE ARE TRADEMARKS OF LOUD TECHNOLOGIES, INC. SPEAKER OUTPUTS PIN PIN PIN 1+ 1 BRIDGED 1+ 2+ 1+ 1 PIN CH 2 2+ 2 1+ 1 CH 1 10 FRS SERIES AMPLIFIERS FILTER SUBSONIC @ 30Hz CLIP LIMIT AMP MODE 10 11 12