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A. INTRODUCTION Thank you for your purchase of the KRELL MDA-300 or MDA-500 power amplifiers. These amplifiers represent the latest evolution in amplifier technology and incorpo- rate many innovative design features. To obtain the best performance from your MDA-300/ 500s, careful attention should be paid to placement, installation and operation. A thoro~ugh understanding o.f these details will help insure satistactory op.eration and long life for the MDA-300/500s and related system com- ponents.
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TABLE OF CONTENTS 4. UNPACKING AND ASSEMBLY BASIC INSTALLATION AND OPERATION INPUT AND OUTPUT CONNECTIONS 8. AMPLIFIER OPERATION 9. PROTECTION CIRCUITRY 10. REAR PANEL DES CRIPTIONS 12. QUESTIONS AND ANSWERS 14. SPECIFICATIONS 15. WARRANTY AND SERVICE INFORMATION 3
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B. UNPACKING AND ASSEMBLY NOTE: Do to the extreme weight of the MDA-300 or MDA-500 it is strongly advised that unpacking and placement is completed by at least two individuals. 1. Open the box on one end. 2. Fold back the flaps on all four sides of the box and carefully roll it over on to the exposed end. 3. Pull the box straight up and off exposing the foam packing material. 4. Pull the foam piece from the exposed end of the ampli- tier. 5. Roll the amplifier carefully onto its handles and re-
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C. BASIC INSTALLATION AND OPERATION 1. Place the MDA-300/500, on a firm level surface away from excessive dirt or moisture. Ideally the amplifiers ’ should be placed as close, to the speakers as possible. ,It is always preferable torun long interconnect cables to tt~e amplifiers and keep speaker cable length t.o a minimu~m.. Speaker cable does add an impedance at tt~e output ot the amplifier, regardless of the cable. All KRELL amplifiers will drive the lowest im. p.edances with ease. When imped-
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D. INPUT AND OUTPUT CONNECTIONS CAUTION: When making connections to this component or any other, make sure ttie power amplifiers are OFF and the preamplifier is in the MUTE or STANDBY mode. 1. Connect the speaker cables to the output terminals of each amplifier. The MDA-300/500s utilize two sets of parallel 5 way binding posts for the left and fight amplifi- ers. This con_figuration makes cable connections and-bi- wiring simple. NOTE: The binding, posts are of the highest quality but w. ill brea
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Thepin assignment for the XLR is: pin _1-= shiel-d (ground) p!n 2 = non-inverting input (hot) pin 3 = inverting input NOTE: The RCA center conductor for each channel is wired_in, parallel with pin 2, the non-inv, erted input. Only one ot these inputs Should be connectecl to a preamplifier. 3. Insert the AC pow6r cord into the receptacle located on the back of eachMDA-300/500. Insert tile other end into the wall AC receptacle. (Refer to section C, Basic Instal- lation and Operation, for AC power
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E. AMPLIFIER OPERATION 1. Push the black button on the front of both amplifiers to turn them on. The blue LED on the front panels above each switch will illuminate. When turning on the system, the amplifiers should al- ways be last.-The MDA-300/50.0s On/Off switch is part of a multi-level turn-on circuit that goes through several steps of protection. Upon turn-on, the amplifier’s outputs are not connected to the.speak.ers. After ttie protect!on circuits have determined that the unit has complete
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E PROTECTION CIRCUITRY There are no fuses in the MDA-300/500s. The amplifiers are protected by a series of non-intrusive, opto-coupled circuits that constantly evaluate the amplifier’s operation. Appropriate protecti’ce action exists for DC conditions, stiort circuit, oscillatidn, AC power anomalies, high ground resistance and out-of:phase ground. Collectively tlae protection circuitry is designed to avoid damage to the amplifiers or speakers caused by other d.efecti~e components, faulty wiring,
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H. REAR PANEL DESCRIPTIONS All descriptions are for each amplifier chassis INPUTS: Balanced via 3 pin XER connector Single ended via RCA connector XLR PIN CONFIGURATION p!n 1 Shield (ground) p.ln 2 Non-inverting or 0 degrees (hot) pan 3 Inverting or 1-80 degrees OUTPUT: Two pairs of five-way binding posts in parallel OTHER: Standard AC receptacle 20 amp circuit breaker OPTIONS: Black Faceplate 11
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I. QUESTIONS AND ANSWERS Q. Should I leave the MDA-300/500 on at all times? A. Although you could leave the MDA-300/500 on at all times without fear of damage to the amplifier, we recom- mend. 30 minutes of warm-up before critical listening and switching the amplifier off when not in use. When Ipush the power button on the front of the ~ DA-300/-500, the amplifier doesn’t turn on. What should I c[o? A. Unplug the amplifier from the AC receptacle and remove the input from the amplifier. Check the
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Q. After the amplifier is on for about one hour it be- comes very hot. Is this normal? A. Yes. Due to the high bias design of the MDA-300/500 it will become quite warm. After approximately 1 hour the amplifier will be at its optimum operating tempera- ture. If the amplifier should-have a severe temperature inbalance between the. left and right channel, unplug the unit and call your aut~0rized dealer or Krell. Q. I tried a new preamplifier in my audio system and when I turned the unit on the MDA-
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J, SPECIFICATIONS MDA-300 MDA-500 GAIN GAIN 26dB 26dB SIGNAL-TO-NOISE SIGNAL-TO-NOISE 106dB unweighted 106dB unweighted THD THD 1K at 8 ohms 1K at 8 ohms less than .2% less than .2% 20K at 8 ohms 20K at 8 ohms less than .4% less then .5% INPUT IMPEDANCE INPUT IMPEDANCE 47,000 ohms (47K) 47,000 ohms (47K) INPUT SENSITIVITY INPUT SENSITIVITY 2.5 volts for 300 watts out 3.2 volts for 500 watts out OUTPUT IMPEDANCE OUTPUT IMPEDANCE ¯ 15 ohms .2 ohms OUTPUT VOLTAGE OUTPUT VOLTAGE 139 volts peak to pe
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K. WARRANTY AND SERVICE INFORMATION There are no user-serviceable parts inside the MDA-300/ 500. The MDA-300/500 has a limited warranty of f~ve years parts and labor. Return freight is included in ~the warranty. The warranty period b.egins on thee date ot p_u_rchase and is activated with the return ot the enclosed Warran.ty Card and a copy of the Sales receipt. Please return the warranty cardimmediate!y after successful installation and operation are completed. The warranty for Krell products is
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KRELL INDUSTRIES 35 HIGGINS DRIVE MILFORD CT 06460 SALES 203-874-3139 FAX 203-878-8373 COPYRIGHT 1992 KRELL INDUSTRIES (MDA9204)
