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 technologyand incorporate manyinnovative design features. To obtain the best performance from your MDA-300/ 500s, careful attention should be paid to placement, installation and operation. Athoro~ughunderstandingo.f these details will help insure satistactory op.eration and long life for the MDA-300/500s and related system components.
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.
B. UNPACKING AND ASSEMBLY NOTE:Do to the extreme weight of the MDA-300 or MDA-500 it is strongly advised that unpacking and placementis completedby at least two individuals. 1. Openthe box on one end. 2. Fold back the flaps on all four sides of the box and carefully roll it over on to the exposedend. 3. Pull the box straight up and off exposingthe foam packing material. 4. Pull the foampiece from the exposedend of the amplitier. 5.
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 ’ shouldbe placedas close, to the speakersas possible. ,It is alwayspreferable torun long interconnect cables to tt~e amplifiers and keep speaker cable length t.o a minimu~m.. Speakercable does add an impedanceat tt~e output ot the amplifier, regardless of the cable. All KRELL amplifiers will drive the lowest im. p.edances with ease.
D. INPUT AND OUTPUT CONNECTIONS CAUTION: Whenmaking connections to this component or any other, makesure ttie poweramplifiers are OFFand the preamplifier is in the MUTE or STANDBY mode. 1. Connectthe speaker cables to the output terminals of each amplifier. The MDA-300/500s utilize two sets of parallel 5 waybindingposts for the left and fight amplifiers. This con_figuration makescable connectionsand-biwiring simple. NOTE: The binding, posts are of the highest quality but w.ill breakif over.tigla.tened.In..
Thepin assignment for the XLRis: pin _1-= shiel-d (ground) p!n 2 = non-inverting input (hot) pin 3 = inverting input NOTE:The RCAcenter 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 ACpow6r cord into the receptacle located on the back of eachMDA-300/500.Insert tile other end into the wall ACreceptacle.
E. AMPLIFIER OPERATION 1. Pushthe black button on the front of both amplifiers to turn them on. The blue LEDon the front panels above each switch will illuminate. Whenturning on the system, the amplifiers should alwaysbe 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. Uponturn-on, the amplifier’s outputs are not connectedto the.speak.ers.
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. Appropriateprotecti’ce action exists for DCconditions, stiort circuit, oscillatidn, ACpoweranomalies,high groundresistance and out-of:phase ground. Collectively tlae protection circuitry is designedto avoid damageto the amplifiers or speakers causedby other d.
H. REAR PANEL DESCRIPTIONS All descriptions are for each amplifier chassis INPUTS: Balanced via 3 pin XERconnector Single ended via RCAconnector XLR PIN CONFIGURATION p!n 1 Shield (ground) p.
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 damageto the amplifier, we recommend.30 minutes of warm-upbefore critical listening and switching the amplifier off whennot in use. WhenIpush the powerbutton on the front of the ~DA-300/-500, the amplifier doesn’t turn on. What shouldI c[o? A. Unplugthe amplifier from the ACreceptacle and removethe input from the amplifier.
Q. After the amplifier is on for about one hour it becomes 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 optimumoperating temperature. 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 myaudio system and when I turned the unit on the MDA-300/500 shut off.
J, SPECIFICATIONS MDA-300 MDA-500 GAIN 26dB GAIN 26dB SIGNAL-TO-NOISE 106dB unweighted SIGNAL-TO-NOISE 106dB unweighted THD 1K at 8 ohms less than .2% THD 1K at 8 ohms less than .2% 20K at 8 ohms less than .4% 20K at 8 ohms less then .5% INPUT IMPEDANCE 47,000 ohms (47K) INPUT IMPEDANCE 47,000 ohms (47K) INPUT SENSITIVITY 2.5 volts for 300 watts out INPUT SENSITIVITY 3.2 volts for 500watts out OUTPUT IMPEDANCE .
K. WARRANTYAND 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. Returnfreight is includedin ~the warranty. Thewarrantyperiod b.egins on thee date ot p_u_rchaseand is activated with the return ot the enclosed Warran.tyCard and a copy of the Sales receipt. Please return the warranty cardimmediate!yafter successful installation and operation are completed. Thewarrantyfor Krell products is valid ~n~in t.
KRELL INDUSTRIES 35 HIGGINS DRIVE MILFORDCT 06460 SALES203-874-3139 FAX203-878-8373 COPYRIGHT1992 KRELL INDUSTRIES (MDA9204)