Cat. No.
FEATURES Your new Ratio Shad< N/PA-31 20Watt AC/McAJte PA Ampfififfl- gives you 20 Watts of sofid power for your PA system. Its wkJe frequency response easiy handles amplification of voice and music. It o p i a t e s on either 120 volts AC or 12 vdts DC power so you can use it in meeting halls and auditDriums, at sports evets, in sdnools, in the office for paging systems — ariywtTere you need to d ^ e r special arvKXincemeits with great sound.
PREPARATION PLACING THE AMPUFCR Before you use you amftffier, be aire you choose a kxation with adequate ventilation. Do not ptebce the ampfifier on thick carpeting (wtiich can restrict ttis air fkiw) or n ^ a heat souce, ajch as a heat vent or radiator (wtvch can cause Vhe ampfifier to overheat). PRESETTMG THE CONTROLS Setting the Amplifier Warrang:A sudden high output from the amplifter coukj damage yotr hearing or the speakers connected to the ampHfia-'s output. Control PO\NER MIC 1, MC 2, PHOISHD/AUX.
CONNECTING AUDIO COMPONENTS TO THE AMPUFIER You can connect optional comporents (such as miCTophones, tuners, turntables, or CD players) to your amplifier to expand your system. Your tocal Radio Shack store canies a wide selection of audio components, adapters, microphones, and speakers. Cautton: Make sure you make all ttie connections to ttie anrtplifier and ^aeakers before connecting and tuming on power.
PUCING THE SPEAKERS Sf»aker ptecanait depencte on your room's size and anrangerr^it We recommaxJ you piay a wide-range recorcfing and experiment with speaker placement until you firto the locations ttrat result in the best sound. The foBowing drawings ^x)w recommerxjed qjeaker placements for typical, nanow, aixl wkJe sound coverage. lypteal Covofsge *^oo9•$oo9-Q009. .QooQ- I#l't\ Sngia Spsaksr (Nanow Ccwsrsse) b 0 0 Use the ^tortest latgth of wire possitde to connect the qaeakers.
• Speakers are connected in series when the first ^Deaker's poative termrial is corBiected to the next speaker's negative terminal. Determine the total speaker impedance of speakers connected in series by adcBng up the individual impedances of afl the connected speakers. Phasing the Spe^ricers Proper ptia^g is important when you use more ttian one speaker in ttie same room or area. Out-of-phase speakers can lose up to one-half of ttieir potential volume, and can have a significantty decreased bass effect.
For exam|:te, if you plan to connect two 8-ohm speakers in paraUel, divide 8 (the impedance of one speaker) by 2 (the rsjmber of speakers) f a a total speaker impec^ce of 4 ohms. COM 4 0 8 0 160 70V 8Q^ Connecting Orriy One Speaker Connect the speaker's negative (-) terminal to the amplifier's COM tenrrwial. Then connect the ^leaker's positive (-F) terminal to the terminal that matches the speaker's impedance (4Q, 8Q, or 16Q).
Connecting Speakers in Parallel 1. Group the four speakers into two pairs. Fdtow these steps to connect speakers in parallel. 2. Connect eadi pair of speakers in series. The total impedance of each pair is 16 ohms (8 + 8 = 16). CDM 4 0 8 0 160 70V 3. Connect the two pairs of speakers in parallel. The total impedance of both pairs is 8 ohms (16 / 2 = 8). 1. Connect the speakers' negative (-) tenninals together. 2. Connect the speakers' positive (-F) tenninals together. 3.
Line transformers have several connectors cafled taps. The primary taps (on one side of the transfonnner) are the inputs and are rated in watts. The secondary taps (cff) the opposite sicte of the transformer) are the outputs and are rated in ohms. {SECONDARY) Cauttons: • Before you connect the speakers, be ajre the total wattage of the primary taps you intend to use does not exceed the ampfifier's maximum 20watt output power rating. • Avoid multiple connections to the amplifier's 70V and COM terminals.
Cautinn: • Your vehide must have a negativeground dectrical system. If you are unsure about what type of electrical system your vehide has, ask your vehide dealer. Cautfanu Use only an identical 5 x 20 mm, fast-acting, 2-amp, 250-volt fuse (such as Cat. No. 270-1052). Foflow these steps to replace tiie ampfifier's fuse. 1. Unpfijg the ampfifier's power cord. • Disconnect the AC conj before you connect tiie DC power cable.
VEHICLE INSTALLATION Before you install ttie ampfifier in your veNcle, read the foltowing hints to help you select a proper mounting location: • OKWse a mounting location in your vehide where all ttie amplifier's controte are easy to reach but do not interfere with ttie operation of the vehide. Ttie most common location is under ttie dashboard directly over ttie drive shaft hump. • Be sure all wires and cables are away firom the brake, clutch, and accelerator.
US6NG YOUR AMPUFSER 1. & t PH0N0/AUX.CD on the back of tiie asnfMBt to PHCM^iO or AUX.O) dependir^ on whidi fiiput soirce yoj want to mb(. 3. Start play on ttie aiKlto input soiree. 4. Set MASTER VOLUME to 10 (mid position). MASTCR VWJUMC • IS MJXXD VAS |«i« a./ ^fl •*v B*V^ @ • The micnophones connected to MIC 1 and MIC 2 and tiie audto input source connected to eitiier tiie PHONO or AUX.CD input jacks are all used at tine same time. • You can connect input sources to PHONO and AUX.
7. Adust TONE toward LOW to adjust the sound toward a bw fi-equency tone, or toward HIGH to adjust it toward a high frequency tone. OMOXAUX.CS MIN tiMt TONC LOW HXMI • ^ Notes: • Leaving TONE set at tiie mid position produces a flat, unacQusted tone. • If feedback occurs, ftjm TONE toward LOW or tum down the volume. 8. Press POWER to ttjm off tiie ampfifier.
TROUBLESHOOTING Your N^A-31 Ampfifier ^KuJd require vay fittte maintenaiiue. If yoj do have problans, refer to ttis chat for posatde adutiars. If yoi csffnot soto the probton, cottact your locd Radto Shack ^ore tor assstance. Nottwig works If you are ifiing AC pcmer. - Qeck tiie AC tase (an tte track peffei). ff t t s fuse is btanm. r^idace it witii a 2-An^, 2S0-ydi t e e ( a e T^qafBcgrg the Ampfifier's Fuse' on Page 10). - CtTBck to rreisaatsethBAc auflet hee pouKr.
CARE AND MAINTENANCE Your new Radto Shack MPA-31 20Watt A(^ot)ite PA Ampfifier is an exampto of superior design and craftsmanship. The fofiowing suggestions wiD help you care for ttie amplifier so you can enjoy it for years. M(xlifying or tampering with tine ampfifier's intemal components can cause a malfunction and might invalidate tine wananty. If the ainplifier is not perfomning as it shouto, take it to your local Radio Shack store for assistance. Keep tiie amplifier dry.
SPECIRCATIONS (ii^xit Poww at 4 C»Tms 1 W4z, 1 0 % T m Power BandMslth at 5W, 10% THD, A M Irput 20 Watte 193 Hz-20 kHz T.H.D at lOW, 1 kHz wflth a) kHz Low Pass Fiter M1C1 MIC 2 AUX.CD PHONO 022% 0,21 % 0.20% 0.24% Input Sensitivity at 10% THD, 1 kHz MIC 1 MIC 2 AUX.CD PHONO Z5mV 2^mV 150 mV 2^nriV Signal to Nose Ratio (Input Shortaj) witin 30 kHz Low Pass FBter MIC 1 MIC 2 AUX.CD PHONO Frequency Response at 4 OTTTS -F 1/-3 dB M1C1 M1C2 AUX.
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RAOIO SHACK LIUfTED WARRANTY This product is warranted against defects for 1 year from date of purchase from Radio Shack company-owned stores and authorized Radio Stiack franci lisees and dealers. Within this period, we will repair it wrttiout charge for parts and labor. Simply bring your R s t o Shack mIes slip as proof ot purchase date to any Radio Shack store. Warranty does not cover transportation costs. Nor does It cover a product subjected to misuse or accidental damage.
