Radio Shack MPA-125 manual

Owner’s Manual Please read before using this equipment. MPA-125 100-Watt PA Amplifier 32-2003.fm Page 1 Tuesday, March 28, 2000 10:45 AM[...]

2 ˆ Contents Features ........... .............. .............. .............. .............. ................. .............. .............. ...... ........ .... 3 Preparation ......... .............. .............. .............. .............. .............. .............. .............. ........ ... ....... 4 Presetting the Controls ..........[...]

3 Features 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 ea sily handles am- plification of voice and music. Use it in meet- ing halls and auditoriums, at sports eve nts, in schools, and in the office for paging systems – anywhere [...]

4 Preparation ˆ Preparation PRESETTING THE CONTROLS Before you begin making connection s or using your amplifier, preset the audio inpu t source’s and the amplifier’s controls to avo id over-driving a channel o r producing sudden unexpected loud sounds. Presetting Audio Input Devices Set the audio input sources’ controls to these levels: Pre[...]

5 Connections MOUNTING THE AMPLIFIER You can mount the ampl ifier in a standard- sized audio equipment rack or on a desk, shelf, or table. Be sure you place it in a loca- tion with adequa te ventilatio n. Do not put it on thick carpeting (which can restrict air flow) or near a heat source such as a he at vent or radiator (which can cause it to over[...]

6 Connections Notes: • If your microphone’s cord is longer than 20 feet (6.01 meters), we recommen d that you connect it to a balanced jack to reduce signal hum. • If you connect a microphone to both jacks for MIC 1 , MIC 2 , MIC 3 , or MIC 4 , the microphon e you connect to the unbalanced jack has priori ty . • If you connect a microphone [...]

7 Connections Connecting an Auxiliary Sound Source You can connect any high-level sound source , such as a CD player, tape deck, or tuner, to the CD/AUX jack on the b ack of the amplifier. 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 microphon es (or six[...]

8 Connections CONNECTING THE SPEAKERS You can connect one or more 4-, 8- or 1 6- ohm speakers to the amplifier, with or with- out transformers. To ensure equal vol ume from each speaker, all connected spe akers should have the same impedance rating. Proper phasing is important when you use more than one speaker in the same room or area. Out-of-phas[...]

9 Connections You can achieve a proper total impedance by combining se ries and parallel connec- tions. Preparing the Speaker Wire Use the shortest length of wire possible to connect the speakers. After placing the speakers, use th is table to de termine th e wire length and ch oose the approp riate gauge size: Note: If you connect speakers without[...]

10 Connections Connecting T wo Speakers In Parallel Follow these steps to co nnect speakers in p arallel. 1. Connect both speaker ’ s negative (–) terminals to ea ch other , th en connect both wires to the COM terminal on the back of the amplifier . 2. Connect both speake r ’s positive (+) terminals to each other , then connect both wires to [...]

11 Connections 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 conne ction described above is also 8 ohms. Like- wise, the total speaker impedance is[...]

12 Connections Follow these steps to connect speakers using a transfo rmer. Connect a wire from 70V RMS on the back of the amplifier to the transformer’s desi red 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. If you want a particular speaker to have a high er volume level, conne[...]

13 Connections SAFETY INDICATORS Your amplifier has two indicators that warn you of potential dama ge to the amplifier. The CLIPPING indicator lights when a soun d source’s signal exceeds its mixing control setting. If this happens, reduce the leve l of the appropriate mi xing control or reduce MASTER VOLUME until the indicator flickers only at p[...]

14 Connections USING THE FEEDBACK FILTER The FEEDBACK FIL TER control lets you reduce or eliminate squeal and other noise caused by feedback. After you adjust MASTER VO L UME , MIC 1 , MIC 2 , MIC 3 , MIC 4 /PHON O , and CD/AUX , turn on the amplifier and any connected sound source. If you he ar any feedback, turn FEEDBACK FIL TER clockwise until y[...]

15 Troubleshooting ˆ T roubleshooting We do not expect yo u to have any problems wi th your RadioSha ck MPA-125 100-Watt PA Am- plifier, but if you do have a problem, this chart mi ght help. If not, take the amplifie r to your loca l RadioShack store for assistance . Symptom Possible Cause Suggestion No power . The fuse might be blown. Check the a[...]

16 Care and Maintenance ˆ Care and Maintenance Your RadioShack MPA-125 100-Watt PA Amplifier is an examp le of superior design and craftsmanship. The following su ggestions will help you care for your ampli fier so you can en- joy it for years. Keep the amplifier dry. If it gets wet, wipe it dry immediately. Liquids might con- tain minerals that c[...]

17 Care and Maintenance REPLACING THE FUSE If the amplifier does not op erate, 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. Caution: Do not use a fuse with ratin gs[...]

18 Specifications ˆ Specifications Output Power at THD 2%, 8 Ohm Lo ad 1 kHz ................................................................................... 10 0 W T otal Harmonic D istortion (at 70 W atts, 8 ohms, 1 kHz, with Band Pass Filter) MIC (Phone Jack) ................................. .................................................[...]

19 Notes ˆ Notes 32-2003.fm Page 19 Tuesday, March 28 , 2000 10:45 AM[...]

32-2003 03A00 Printed in China RadioShack A Division of Tandy Corporation Fort Worth, Texas 76102 Limited One-Y ear W arranty This product is warranted by RadioShack against manufactu ring defects in material and workman- ship under normal use for one (1 ) year from t he da te of pu rchase from Radi oSha ck compan y- owned stores and authorized Rad[...]