Krell Industries Power Amplifiers MDA-300/500 Quick start guide

A. INTRODUCTION

Thankyou for your purchase of the KRELLMDA-300or

MDA-500poweramplifiers. These amplifiers represent

the latest evolution in amplifier technologyandincorpo-

rate manyinnovative designfeatures.

Toobtain the best performancefrom your MDA-300/

500s, careful attention shouldbe paid to placement,

installation andoperation. Athoro~ughunderstandingo.f

thesedetails will help insure satistactory op.erationand

long life for the MDA-300/500sand related systemcom-

ponents.

This Owner’sReferenceis divided into several sections,

eac.hdesignedto perfo__r~_,a different function.Asyou

.read throughthis. O.w.ners Referenceyouwill become

better acquaintedwith the features andfunctions that

makethe MDA-300/500sa superb value. A Question and

Answersection is also included whereanswersto com-

monquestions are provided. Shouldyouhave any ques-

tions or suggestionsplease feel free to contact yourau-

thorized dealer or the KRELLstaff for assistance.

In the unlikely event that your MDA-3.00/50.0sshould

requireserviceyouwill be pleasedto ~now~tlaat it is .

backedby a.comprehensiveCustomerbatistaction.policy

andoneof the mostadvancedservice facilities in the

industry. For detailed informationon the terms andcon-

ditions of service, pleaseconsult yourwarrantyreg.istra-

tion card, yourauthorized KRELLDealer or Distributor.

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. WARRANTYAND SERVICE INFORMATION

B. UNPACKING AND ASSEMBLY

NOTE:Doto the extreme weight of the MDA-300or

MDA-500it is strongly advised that unpackingand

placementis completedby at least twoindividuals.

1. Openthe boxon one end.

2. Foldbackthe flaps on all four sides of the boxand

carefully roll it overonto the exposedend.

3. Pull the boxstraight upand off exposingthe foam

packingmaterial.

4. Pull the foampiece fromthe exposedendof the ampli-

tier.

5. Roll the amplifier carefully ontoits handlesandre-

movethe secondpiece of foam.

Thefollowing items will nowbe visible in each box:

1MDA-300/500monaural amplifier

1 Warrantycard

1ACpower cord

4 or 5 Rubberbottoms (MDA-500has 5 feet)

NOTE:If any of these items are not included please

contact yourauthorized dealer immediatelyf6r assis-

tance.

6. Removethe plastic bag fromthe amplifier.

7. Repeatprocedurefor the secondamplifier.

NOTE:Saveall pac.kin~gmaterials..If youmustship your

MDA-300/500sin the tuture, repackthe unit in its origi-

nal packagingto prevent transit damage.

CAUTION:Donot connect the powercords into the AC

mainsbefore completingthe Installation section.

C. BASIC INSTALLATION

AND OPERATION

1. Place the MDA-300/500,on a firm level surface away

fromexcessivedirt or moisture. Ideally the amplifiers ’

shouldbeplacedas close, to the speakersas possible. ,It is

alwayspreferable torun long interconnect cables to tt~e

amplifiers andkeepspeakercable length t.o a minimu~m..

Speakercable doesadd an impedanceat tt~e output ot the

amplifier, regardless of the cable. All KRELLamplifiers

will drive the lowest im. p.edanceswithease. Whenimped-

anceis added,the amphfier’spoweris litera.lly wastedin

driving cable. Longspeaker cables reduce tlae maximum

powerthat can be dehveredto the speakers.

2. Amplifiers dissipate muchof the powerthey consume

in heat. TheMDA-300/500sshould-be installed in a

location that.provides unobstructedventilation. If you

haveto install the units onshelvesor in a cabinet, extra

ventilation m~¢be necessary_. This can be accomplished

with "whisper- type fans. Consultyourdealer for assis-

tance.

Generally,withthe front andrear of a cabinet open,2-3

inches of clearance oneach side and8 inches of clear-

ance abovethe amplifiers should provideadequateventi-

lation.

The exact dimensions for the MDA-300and MDA-500

are in the Specifications Sectionbelow.

3. TheMDA-300/500sshould have a dedicated 20.amp.

line for eachamplifier and shouldonly be operatedwith

the powercords supplied. Useof other powercords may

damagethe amplifiers or void its warranty. Please consult

KREELor your dealer BEFOREusing any devices de-

signedto alter or stabilize the ACpow.erfbr.the MDA-

300/500s. If youhave any questions about placementor

ACpowerconditions please consult KREL-L.

4. Thefeet on the MDA-300/500scanbe used in several

different ways. Theyare madefrom machinedDelrin and

are suppliedwitla separate threadedrubberb~ottoms.The

rubberbottomscan be screwedinto the feet tor protec-

tion of fragile surfaces suchas hardwoodfloors or furni-

ture. For use on rugs, werecommendusing the fee.t with-

out the rubber bottoms. MDA-300/500sfeet can also

accept the KREL.L AMDs(A, coustic MassDamper).

Theseimprovethe amplifier s sonic performancein most

installations.

D. INPUT AND OUTPUT

CONNECTIONS

CAUTION:Whenmaking connections to this component

or anyother, makesure ttie poweramplifiers are OFFand

the preamplifier is in the MUTEor STANDBYmode.

1. Connectthe speakercables to the output terminals of

each amplifier. TheMDA-300/500sutilize two sets of

parallel 5 waybindingposts for the left andfight amplifi-

ers. This con_figurationmakescable connectionsand-bi-

wiringsimple.

NOTE:Thebinding, posts are of the highest quality but

w.ill breakif over.tigla.tened.In..se.rt wireor spadeluginto

the connectoranc~tigt~ten until there is no movement

fromthe cable.

CAUTION:Makesure all cable terminations are of the

highest quality, free fromfrayedends, shorts or cold

solderjoints.

2. Connectthe interconnect cables fromyour preampli-

fier to the input of each MDA-300/500.

Thewiring to andfromthe amplifiers, and all compo-

nents in general, shouldbe arrangedin a neat, organized

manner.Specifically, ACwires should be separated from

audio wires. This practice avoids humor ottier unwanted

noise frombeing inducedinto the system.

The MDA-300/500shave balanced and single-ended

inputs. Thebalanced inputs use 3-pin XLRconnectors

and the single-ended inputs use standard RCAconnec-

tors.

CAUTION:Useonly one input to the amplifier at a time.

TheMDA-300/500sare shipped with. shorting pins in the

~LRinputs. Thesepins shoi~ld remainin the XLRinputs

it youare operating the MDA-300/500sin the single-

elided mode.Whenthe shorting pin is inserted, pin 1 and

pin 3 are. shortedtogether. Thesfiorting pins mustbe

removeclto connect the MDA-300/500sfor balanced

operation.

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

oneot these inputs Shouldbe connectecl to a preamplifier.

3. Insert the ACpow6rcord into the receptacle located on

the back of eachMDA-300/500.Insert tile other end into

the wall ACreceptacle. (Refer to section C, Basic Instal-

lation and Operation, for ACpower requirements)

E. AMPLIFIER OPERATION

1. Pushthe blackbuttononthe front of bothamplifiersto

turn themon. Theblue LEDon the front panels above

eachswitch will illuminate.

Whenturning on the system,the amplifiers shouldal-

waysbe last.-The MDA-300/50.0sOn/Offswitch is part

of a multi-level turn-oncircuit that goesthroughseveral

steps of protection. Uponturn-on, the amplifier’s outputs

are not connectedto the.speak.ers. Afterttie protect!on

circuits havedeterminedthat the unit has completely

stabilized, the speakerrelays will be engaged.-Youwill

hear a click at this point. Theamplifiers are nowreadyto

use. Theamplifiers will be at temperatureandsoundtheir

best after approximately30 minutes.

2. Withthe preamplifier in the Muteposition, or volume

control fully attenuated, select a source. Turnthe volume

controlup to yourdesired listening level.

3. Understandingthe operationof these amplifiers is very

e.asy. Equallyimportantis an understandingof the care

that should be exercised whenoperating the systemas a

whole,in relation to the enormouspoweroutput of the

MDA-300/500s.Simple mistakes, such as switching

betweenactive sources without mutingthe preampfifier

9utput, or bumping/miscuinga cartridge, can generate

large transients at lowfrequencies.Withthis type of

transient the MDA-300/500scan generate enoughpower

to damagemostloudspeakers. AII switching of sources

should be donewith the preamplifier level e~ther muted

or fully attenuated. Inputs to the amplifier shouldnot be

changedwhilethe amplifier is on.

NOTE:Care must be taken whensetting high playback

levels. Becauseof their tremendousreserve of-clean

power,KRELLamplifiers safely drive speakers to higher

soundpressurelevels than other amplifiers. Thisalso .

meansdriving the speakersto their fimit. Alwaysturn the

level downat the first sign of distortion.

Whenturning the systemoff, the amplifiers should

ALWAYSbe first. This avoids the possibility of a turn-

off transient fromsomeother componentgetting to the

speakers.

E PROTECTIONCIRCUITRY

Thereare no fuses in the MDA-300/500s.Theamplifiers

are protected by a series of non-intrusive, opto-coupled

circuits that constantlyevaluatethe 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 avoiddamageto

the amplifiers or speakerscausedbyother d.efecti~e

components,faulty wiring, mishandlingof the systemoy

amplifierfailure. Whenthe protection, circuit is engage(l,

the a.mplifierswill shut off andshort tlaeir output.After

resolving either the input or outputproblemthe amplifi-

ers can15eturnedon.

Theamplifiers also havecircuit breakers ontheir

backpanelfor the ACpower.Shouldthe button in the

center of the breakerpopout, pushit in to reset the

breaker.If the amplifiersstill donot comebackon, call

Krell Industries.

H. REAR PANEL DESCRIPTIONS

All descriptions are for eachamplifier chassis

INPUTS:

Balancedvia 3 pin XERconnector

Single ended via RCAconnector

XLR PIN CONFIGURATION

p!n 1 Shield (ground)

p.ln 2 Non-invertingor 0 degrees(hot)

pan3 Inverting or 1-80degrees

OUTPUT:

Twopairs of five-waybindingposts in parallel

OTHER:

Standard ACreceptacle

20 ampcircuit breaker

OPTIONS:

Black Faceplate

This manual suits for next models

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