Radio Shack MPA-125 Owner's Manual
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Radio Shack MPA-125 Owner's Manual

100-watt pa amplifier
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32-2003.fm Page 1 Tuesday, March 28, 2000 10:45 AM
MPA-125 100-Watt PA Amplifier

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Summary of Contents for Radio Shack MPA-125

  • Page 1 32-2003.fm Page 1 Tuesday, March 28, 2000 10:45 AM MPA-125 100-Watt PA Amplifier...

  • Page 2: Table Of Contents

    32-2003.fm Page 2 Tuesday, March 28, 2000 10:45 AM ˆ Contents Features ... 3 Preparation ... 4 Presetting the Controls ... 4 Presetting Audio Input Devices ... 4 Presetting the Amplifier ... 4 Mounting the Amplifier ... 5 Placing the Speakers ... 5 Connections ...

  • Page 3: Features

    32-2003.fm Page 3 Tuesday, March 28, 2000 10:45 AM ˆ Features Your RadioShack MPA-125 100-Watt PA Amplifier gives you the versatility and power you need in a professional sound system. Its wide frequency response easily handles am- plification of voice and music. Use it in meet-...

  • Page 4: Preparation

    32-2003.fm Page 4 Tuesday, March 28, 2000 10:45 AM ˆ Preparation PRESETTING THE CONTROLS Before you begin making connections or using your amplifier, preset the audio input source’s and the amplifier’s controls to avoid over-driving a channel or producing sudden unexpected loud sounds.

  • Page 5: Mounting The Amplifier

    32-2003.fm Page 5 Tuesday, March 28, 2000 10:45 AM MOUNTING THE AMPLIFIER You can mount the amplifier in a standard- sized audio equipment rack or on a desk, shelf, or table. Be sure you place it in a loca- tion with adequate ventilation. Do not put it on thick carpeting (which can restrict air flow) or near a heat source such as a heat vent or radiator (which can cause it to overheat).

  • Page 6: Connecting A Turntable

    32-2003.fm Page 6 Tuesday, March 28, 2000 10:45 AM Notes: • If your microphone’s cord is longer than 20 feet (6.01 meters), we recommend that you connect it to a balanced jack to reduce signal hum. • If you connect a microphone to both jacks for you connect to the unbalanced jack has priority.

  • Page 7: Connecting An Auxiliary Sound Source

    CD/AUX Connecting the MIX BUS Jack You can connect another MPA-125 to this jack to double the size of your PA system. This lets you use up to eight microphones (or six microphones and two turntables), and two auxiliary sound sources.

  • Page 8: Connecting The Speakers

    32-2003.fm Page 8 Tuesday, March 28, 2000 10:45 AM CONNECTING THE SPEAKERS You can connect one or more 4-, 8- or 16- ohm speakers to the amplifier, with or with- out transformers. To ensure equal volume from each speaker, all connected speakers should have the same impedance rating.

  • Page 9: Preparing The Speaker Wire

    32-2003.fm Page 9 Tuesday, March 28, 2000 10:45 AM You can achieve a proper total impedance by combining series and parallel connec- tions. Preparing the Speaker Wire Use the shortest length of wire possible to connect the speakers. After placing the speakers, use this table to determine the wire length and choose the appropriate gauge size:...

  • Page 10: Connecting Two Speakers In Parallel

    32-2003.fm Page 10 Tuesday, March 28, 2000 10:45 AM Connecting Two Speakers In Parallel Follow these steps to connect speakers in parallel. 1. Connect both speaker’s negative (–) terminals to each other, then connect both wires to terminal on the back of the amplifier. 2.

  • Page 11: Connecting Speakers With Transformers

    32-2003.fm Page 11 Tuesday, March 28, 2000 10:45 AM 3. Connect the two pairs of speakers in parallel. If you connected 8 ohm speak- ers the total impedance of both pairs is 8 ohms (16 2 = 8). Note: If each of the four speakers is 8 ohms, the total speaker impedance of the combined series/parallel connection described above is also 8 ohms.

  • Page 12: Connecting Power

    32-2003.fm Page 12 Tuesday, March 28, 2000 10:45 AM Follow these steps to connect speakers using a transformer. Connect a wire from on the back of 70V RMS the amplifier to the transformer’s desired pri- mary tap (10, 5, 2.5, 1.25 or 0.62 watts). Note: Usually, each speaker in a system uses the same wattage tap.

  • Page 13: Safety Indicators

    32-2003.fm Page 13 Tuesday, March 28, 2000 10:45 AM SAFETY INDICATORS Your amplifier has two indicators that warn you of potential damage to the amplifier. The CLIPPING indicator lights when a sound source’s signal exceeds its mixing control setting. If this happens, reduce the level of the appropriate mixing control or reduce until the indicator flickers only at peak volume levels.

  • Page 14: Using The Feedback Filter

    32-2003.fm Page 14 Tuesday, March 28, 2000 10:45 AM USING THE FEEDBACK FILTER control lets you reduce or eliminate squeal and other noise caused by FEEDBACK FILTER feedback. After you adjust , and , turn on the MASTER VOLUME MIC 1 MIC 2 MIC 3 MIC 4/PHONO...

  • Page 15: Troubleshooting

    ˆ Troubleshooting We do not expect you to have any problems with your RadioShack MPA-125 100-Watt PA Am- plifier, but if you do have a problem, this chart might help. If not, take the amplifier to your local RadioShack store for assistance.

  • Page 16: Care And Maintenance

    32-2003.fm Page 16 Tuesday, March 28, 2000 10:45 AM ˆ Care and Maintenance Your RadioShack MPA-125 100-Watt PA Amplifier is an example of superior design and craftsmanship. The following suggestions will help you care for your amplifier so you can en- joy it for years.

  • Page 17: Replacing The Fuse

    32-2003.fm Page 17 Tuesday, March 28, 2000 10:45 AM REPLACING THE FUSE If the amplifier does not operate, you might need to replace the fuse on the back of the amplifier with the supplied (or another) 3- amp, 250-volt fuse. Important: Let the amplifier cool down and see if it starts again before you assume a fuse needs to be replaced.

  • Page 18: Specifications

    32-2003.fm Page 18 Tuesday, March 28, 2000 10:45 AM ˆ Specifications Output Power at THD 2%, 8 Ohm Load 1 kHz ... 100 W Total Harmonic Distortion (at 70 Watts, 8 ohms, 1 kHz, with Band Pass Filter) MIC (Phone Jack) ... 0.25% MIC (XLR Jack) ...
  • Page 19 32-2003.fm Page 19 Tuesday, March 28, 2000 10:45 AM ˆ Notes Notes...
  • Page 20 32-2003.fm Page 20 Tuesday, March 28, 2000 10:45 AM Limited One-Year Warranty This product is warranted by RadioShack against manufacturing defects in material and workman- ship under normal use for one (1) year from the date of purchase from RadioShack company-owned stores and authorized RadioShack franchisees and dealers.

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