Krell Industries MDA-300/500 Stereo Amplifier User Manual
Contents
1. qamna MIDA 300 MIDA SOOQ OWNER S REFERENCE A INTRODUCTION Thank kwe 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 thorough understanding of these details will help insure satisfactory operation and long life for the MDA 300 500s and related system com ponents This Owner s Reference is divided into several sections each designed to perform a different function As you read through this Owner s Reference you will become better acquainted with the features and functions that make the MDA 300 500s a superb value A Question and Answer section 1s also included where answers to com mon questions are provided Should you have any ques tions or suggestions please feel free to contact your au thorized dealer or the KRELL staff for assistance In the unlikely event that your MDA 300 500s should require service you will be pleased to know that itis backed by a comprehensive Customer Satisfaction policy and one of the most advanced service facilities in the industry For detailed information on the terms and con ditions of service please consult your warranty registra tion card your authorized KRELL Dealer or Distributor 4 102. 12 14 1 3 TABLE OF CONTENTS UNPACKING AND ASSEMBLY BASIC INSTALLATION AND OPERATION INPUT AND OUTPUT CONNECTIONS AMPLIFIER OPERATION PROTECTION CIRCUITRY REAR PANEL DESCRIPTIONS QUESTIONS AND ANSWERS SPECIFICATIONS WARRANTY AND SERVICE INFORMATION ms NOLLAN www 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 rs Pull the foam piece from the exposed end of the ampli ler 5 Roll the amplifier carefully onto its handles and re move the second ptece of foam The following items will now be visible in each box l MDA 300 500 monaural amplifier l Warranty card l AC power cord 4 or 5 Rubber bottoms MDA 500 has 5 feet NOTE If any of these items are not included please contact your authorized dealer immediately for assis tance 6 Remove the plastic bag from the amplifier 7 Repeat procedure for the second amplifier NOTE Save all packing materials If you must ship your MDA 300 500s in the future repack the unit in its origi nal packaging to prevent transit damage CAUTION Do not connect the power cords into the AC mains before completing the Installation
3. 300 500 was in the system What should I do A Often when a new component is introduced into an audio a a hum may become present This is often caused by a ground loop in the system Try putting a 3 prong to 2 prong AC adaptor cheater plug on the AC power cord lifting the ground from the unit This should make the hum disappear If not try another adaptor else where in the system NOTE Always keep one major audio component grounded NOTE Even though the ground is lifted from the power amplifier it 1s still grounded via the interconnect cables throughout the rest of the system o Q Can I use special audio power cords on the MDA 300 or MDA 500 a A You can experiment with special power cords as long as they are grounded on both ends and meet the amplifier s 15 amp power requirement 12 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 qute warm After approximately 1 hour the amplifier will be at its eu operating tempera ture If the amplifier should have a severe temperature inbalance between the left and right channel unplug the unit and call your authorized dealer or Krell Q I tried a new preamplifier in my audio system and when I turned the unit on the MDA 300 500 shut off Is the amplifier defective A More than likely the amplifier is not defective When connecting components you should alwa
4. d ends shorts or cold solder joints 2 Connect the interconnect cables from your preampli fier to the input of each MDA 300 500 The wiring to and from the amplifiers and all compo nents in general should be arranged in a neat organized manner Specifically AC wires should be separated from audio wires This practice avoids hum or other unwanted noise from being induced into the system The MDA 300 500s have balanced and single ended inputs The balanced inputs use 3 pin XLR connectors and the single ended inputs use standard RCA connec tors CAUTION Use only one input to the amplifier at a time The MDA 300 500s are ki pa with shorting pins in the XLR inputs These pins should remain in the XLR inputs if you are operating the MDA 300 500s in the single ended mode When the shorting pin is inserted pin 1 and pin 3 are shorted together The shorting pins must be removed to connect the MDA 300 500s for balanced operation The pn assignment for the XLR s pin 1 shield ground pin 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 inverted input Only one of these inputs should be connected to a preamplifier 3 Insert the AC power cord into the receptacle located on the back of each MDA 300 500 Insert the other end Into the wall AC receptacle Refer to section C Basic Instal lation and Operation for AC power requireme
5. e done with the preamplifier level either muted or fully attenuated Inputs to the amplifier should not be changed while the amplifier is on NOTE Care must be taken when setting high playback levels Because of their tremendous reserve of clean power KRELL amplifiers safely drive speakers to higher sound pressure levels than other amplifiers This also means driving the speakers to their limit Always turn the level down at the first sign of distortion When turning the system off the amplifiers should ALWAYS be first This avoids the possibility of a turn off transient from some other component getting to the speakers F 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 protective action exists for DC conditions short circuit oscillation AC power anomalies high round resistance and out of phase ground Collectively the protection circuitry is designed to avoid damage to the amplifiers or speakers caused by other defective components ky ial a mishandling of the system or amplifier failure When the protection circuit is engaged the amplifiers will shut off and short their output After resolving either the input or output problem the amplifi ers can be turned on The amplifiers also have circuit breakers on their backpanel for the AC power Should the butto
6. ms 144 pounds K WARRANTYAND SERVICE INFORMATION There are no user serviceable parts inside the MDA 300 500 The MDA 300 500 has a limited warranty of five years parts and labor Return freight is included in the warranty The warranty yan begins on the date of urchase and is activated with the return of the enclosed arranty Card and a copy of the Sales receipt Please return the warranty card immediately after successful installation and operation are completed The warranty for Krell products 1s valid only in the coun try to which they were originally shipped and at the factory If you think there are problems with your unit please contact your dealer distributor or the factory immediately Please do not return any unit to KRELL for repair with out first calling to discuss the problem and to obtain a Return Authorization number Freight to the factory or distributor 1s your responsibility Return freight to you will be paid by the factory or distributor Any unauthorized updates or modifications performed to the unit will void the warranty 15 p eee OAAS UNV AINVADTIVA maw MM KRELL INDUSTRIES 35 HIGGINS DRIVE MILFORD CT 06460 w SALES 203 874 3139 FAX 203 878 8373 COPYRIGHT 1992 KRELL INDUSTRIES MDA9204
7. n in the center of the breaker pop out an it in to reset the breaker If the amplifiers still do not come back on call Krell Industries H REAR PANEL DESCRIPTIONS All descriptions are for each amplifier chassis INPUTS Balanced via 3 pin XLR connector Single ended via RCA connector XLR PIN CONFIGURATION pin1 Shield ground pin 2 Non inverting or 0 degrees hot pin 3 Inverting or 180 degrees OUTPUT Two pairs of five way binding posts in parallel OTHER Standard AC receptacle 20 amp circuit breaker OPTIONS Black Faceplate 11 en IT TNVd AVA Gw L QUESTIONSAND 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 I push the power button on the front of the DA 300 500 the amplifier doesn t turn on What should I do A Unplug the amplifier from the AC receptacle and remove the input from the amplifier Check the output connections then a on amplifier back in Check the circuit breaker on the back of the unit and reset it if nec essary Push the power button on the front panel If the hac persists unplug the unit and call your dealer or rell industries Q When I turn the amplifier on there is a loud hum through the speakers There was never a hum before the MDA
8. nts SNOLLDINNO mauwa rm 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 500s 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 speakers After the protection circuits have determined that the unit has completely stabilized the aS relays will be engaged You will hear a click at this point The amplifiers are now ready to use The amplifiers will be at temperature and sound their best after approximately 30 minutes 2 With the preamplifier in the Mute position or volume control fully attenuated select a source Turn the volume control up to your desired listening level 3 Understanding the operation of these amplifiers is very easy Equally important 1s an understanding of the care that should be exercised when operating the system as a whole in relation to the enormous power output of the MDA 300 500s Simple mistakes such as switching between active sources without muting the preamplifier output or bumping miscuing a cartridge can generate large transients at low frequencies With this type of transient the MDA 300 500s can gen enough power to damage most loudspeakers All switching of sources should b
9. section 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 to run long interconnect cables to the amplifiers and keep speaker cable length to a minimum Speaker cable does add an impedance at the output of the amplifier regardless of the cable All KRELL amplifiers will drive the lowest impedances with ease When imped ance is added the amplifier s power is literally wasted in driving cable Long speaker cables reduce the maximum power that can be delivered to the speakers 2 Amplifiers dissipate much of the power they consume in heat The MDA 300 500s dwa installed in a location that A gc unobstructed ventilation If you have to install the units on shelves or in a cabinet extra ventilation may be necessary This can be accomplished with whisper type fans Consult your dealer for assis tance Generally with the front and rear of a cabinet open 2 3 inches of clearance on each side and 8 inches of clear Me above the amplifiers should provide adequate venti ation The exact dimensions for the MDA 300 and MDA 500 are in the Specifications Section below 3 The MDA 300 500s should have a dedicated 20 amp line for each amplifier and should only be operated with the power cords supplied Use of other power cords may ary the amplifiers or void its
10. warranty Please consult KRELL or your dealer BEFORE using any devices de ane to alter or stabilize the AC power for the MDA 300 500s If you have any questions about ee or AC power conditions please consult KRELL 4 The feet on the MDA 300 500s can be used in several different ways They are made from machined Delrin and are supplied with separate threaded rubber bottoms The rubber bottoms can be screwed into the feet for protec tion of fragile surfaces such as hardwood floors or furni ture For use on rugs we recommend using the feet with out the rubber bottoms MDA 300 500s feet can also accept the KRELL AMDs Acoustic Mass Damper These improve the amplifier s sonic performance in most installations es NOLLVTIVISNI www sssss D INPUT AND OUTPUT CONNECTIONS CAUTION When making connections to this component or any other make sure the 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 ae binding posts for the left and right amplifi ers This configuration makes cable connections and bi wiring simple NOTE The binding posts are of the highest quality but will break if overtightened Insert wire or spade lug into the connector and tighten until there is no movement from the cable CAUTION Make sure all cable terminations are of the en quality free from fraye
11. ys keep the amplifier off The ampliter sensed a bad input signal and shut off protecting itself and the speakers There also could have been a bad cable connection or excessive DC offset coming from the output of the pre amplifier Before turning the amplifier on check the input cables If that doesn t help bring the preamplifier to the dealer for testing 13 mes SUAASNVY ANV SNOLLSYN m J SPECIFICATIONS MDA 300 GAIN 26dB SIGNAL TO NOISE 106dB unweighted THD 1K at 8 ohms less than 2 20K at 8 ohms less than 4 INPUT IMPEDANCE 47 000 ohms 47K INPUT SENSITIVITY 2 5 volts for 300 watts out OUTPUT IMPEDANCE 2 ohms OUTPUT VOLTAGE 139 volts peak to peak OUTPUT POWER All readings are continuous output power per channe 300 watts 600 watts 1200 watts 2400 watts DIMENSIONS 19 0 WIDE 19 5 DEEP with handles 8 5 HIGH with feet SHIPPING WEIGHT 105 pounds 1 ohm 14 MDA 500 GAIN 26dB SIGNAL TO NOISE 106dB unweighted THD 1K at 8 ohms less than 2 20K at 8 ohms less then 5 INPUT IMPEDANCE 47 000 ohms 47K INPUT SENSITIVITY 3 2 volts for 500 watts out OUTPUT IMPEDANCE 15 ohms OUTPUT VOLTAGE 179 volts peak to peak OUTPUT POWER All readings are continuous output power per channe 500 watts 1000 watts 2 ohms 2000 watts 1 ohm 4000 watts DIMENSIONS 19 0 WIDE 24 0 DEEP with handles 8 5 HIGH with feet SHIPPING WEIGHT 8 ohms 4 oh
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