Krell Industries Three-Channel Power Amplifier KAV-250a/3 User manual

Leader in Audio Engineering
KAV-250a
Stereo PowerAmplifier
KAV-250a/3
Three-ChannelPowerAmplifier
Instructionsfor Use,v 99.2
Owner’s Reference

KAV-250aStereo PowerAmplifier and
KAV-250a/3Three-Channel PowerAmplifier
Instructionsfor Use,v 99.2
Cover: KAV-250a/3 Three-ChannelPowerAmplifier
Krell Industries,Inc.
45 Connair Road
Orange, CT 06477-3650 USA
TEL [phone]
FAX[phone]
E-MAILkrell @krellonline.com
WEBSITEhttp://www.krellonline.com
This product complieswith the EMCdirective (89/336/EEC)andthe low-voltage directive
(73/23/EEC).
WARNINGS
Theamplifier mustbeplacedona firm, level surfacewhereit is not exposedto dripping or
splashing.
Theventilation grids onthe top of the amplifier andthe spaceunderneaththe amplifier mustbe
unobstructedat all times during operation. Donot place flammablematerial aboveor beneath
theamplifier.
ContactyourauthorizedKrell dealer, distributor, or Krell beforeusinganydevicesdesignedto
alter or stabilize the ACpowerfor the KAV-250aor KAV-250a/3.
Beforeconnectingthe KAV-250aor KAV-250a/3,makesure the amplifier is off andany output
device(suchas a preamplifier) is in muteor stand-bymode.Makesure all cable terminations
areof the highestquality andfree fromfrayedends,short circuits, or coldsolderjoints.
Useonlyoneset of inputsto the amplifier at a time.
After reconfiguring for MAT,do not usemorethan oneinput at the sametime.
After bridging, donot usebothinputs at the sametime.
THEREARE NO USERSERVICEABLEPARTSINSIDE ANY KRELL PRODUCT
PleasecontactyourauthorizedKrell dealer, distributor, or Krell if youhaveanyquestionsnot
addressedin this reference manual.
Thisproductis manufacturedin theUnitedStatesof America.Krell® is aregisteredtrademarkof Krell
Industries,Inc., andis restrictedfor usebyKrellIndustries,Inc., its subsidiaries,andauthorizedagents.
Multi AmpThroughput
TM is a trademarkof Krell Industries,Inc. All othertrademarksandtradenamesare
registeredto their respectivecompanies.
©1999byKrell Industries, Inc. All rights reserved P/N: I960101710688

Contents
INTRODUCTION’
DEFINITION OF TERMS
UNPACKING
PLACEMENT
ACPowerGuidelines
FRONTPANELDESCRIPTION: KAV-250a
BACKPANELDESCRIPTION: KAV-250a
FRONTPANELDESCRIPTION:KAV-250a/3
BACKPANELDESCRIPTION:KAV-250a/3
CONNECTINGTHEKAV-250a or KAV-250aJ3 AMPLIFIER
TO YOURSYSTEM
Input andOutputConnections
OPTIONAL SYSTEMCONFIGURATIONS
Multi AmpThroughput
Bridged Operation
Examplesof ConnectionScenarios
AMPLIFIER OPERATION
On/Off andOperation
AMPLIFIER TROUBLESHOOTING
Howto Troubleshoot SystemNoise
QUESTION AND ANSWER
WARRANTY
RETURNAUTHORIZATION PROCEDURE
SPECIFICATIONS
Page
1
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2
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10
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14
15
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25
26
26
27
28
29
30
KAV-250aand KAV-250a/3Amplifiers iii

Illustrations
FIGURE1
FIGURE2
FIGURE3
FIGURE4
FIGURE5
The KAV-250aFront Panel
The KAV-250aBack Panel
TheKAV-250a/3Front Panel
The KAV-250a/3Back Panel
Reconfiguring the KAV-250afor MAT
or BridgedOperation
FIGURE6 Reconfiguring the KAV-250a/3for MAT
or BridgedOperation
Page
4
6
9
11
16
19
iv KAV-250aand KAV-250a/3Amplifiers

Introduction
Thankyou for your purchaseof the Krell KAV-250aStereoPowerAmplifier or
KAV-250a/3Three-ChannelPowerAmplifier..
TheKAV-250aandKAV-250aJ3amplifiers provide substantial two- andthree-channel
output powerthat delivers realistic musicproductionat anexceptionalvalue. These
amplifiers canbecustomizedwith a variety of optional systemconfigurations: Multi
AmpThroughput(MAT),bridged operation, and high powermonooperation. These
options provide a wider range of poweroutputs andconnectionoptions. Boththe KAV-
250aandKAV-250a/3amplifiers provide balancedandsingle-endedinputs for
completecompatibility with other components.TheKAV-250aand KAV-250a/3
amplifiers canbeoperatedusing the 12VDCtrigger for other components.Either
amplifier integrates seamlesslyhometheater or whole-housesystems.
This referencemanualcontains importantinformation onplacement,installation, and
operation of the KAV-250aandKAV-250a/3amplifiers. Pleaseread this information
carefully. Athoroughunderstandingof thesedetails helpsensuresatisfactory operation
andlong life for your KAV-250aor KAV-250aJ3amplifier andrelated system
components.
Definition of Terms
Multi AmpThroughput
Aninternal connectionoption that sendsthe samemusicsignal to all amplifier channels
using onebalancedor single-endedconnection. MATreducesinstallation complexity
andcabling requirementsin systemscontainingmultiple amplifiers. MATalso allows a
variety of connectionscenarios,including poweringloudspeakersthat havetwosets of
binding postsandindependentlypoweringmultiple pairs of stereo loudspeakersto
extendthe listening environmentthroughoutyour home.
Bridging
Aninternal connectionoption that links twoamplifier channelsto operateasone
combinedamplifier channel,greatly increasing the channel’spoweroutput.
On
Whenthe powerbutton onthe front panel is pressedandthe blue powerLED
illuminates, the amplifier is onandreadyto playmusic.
Off
Whenthe powerbutton on the front panel is pressedandthe blue powerLEDturns off,
theamplifieris off.
KAV-250aand KAV-250a/3Amplifiers 1

Unpacking
Openthe shipping box, whichcontains:
1 amplifier unit (packedin foamend-caps)
2 ribbon connectioncables
KAV-250afuses:
2 AGC-8(~ ’amp)
1 slow-blow(20 ampfor 100/120V or 12 ampfor 220/240V)
or
KAV-250a/3fuses:
3 AGC-.8 ~ amp)
1 slow-blow(20 ampfor 100/120V or 12 ampfor 220/240V)
1 12 VDCoutput (12 Vtrigger) cable
1 IECconnector(ACpower)cord
1 T-15Torx wrench
1 packetcontainingthe owner’sreferencemanualandthe warrantyregistration
card.
Graspthe undersideof the foamend-capsthat encasethe amplifier andlift the
amplifier straight outof theshippingbox.
Placethe amplifier in a safelocation andremovethe protective plastic wrapping.
Notes
If anyof theseitemsare not includedin the shippingbox,pleasecontactyour
authorizedKrell dealer,distributor, or Krell for assistance.
Saveall packingmaterials.If youshipyouramplifier in the future, repackthe unit in its
original packagingto prevent trans# damage.SeeReturnAuthorization Procedure,
onpage29, for moreinformation.
2KAV-250aand KAV-250aJ3Amplifiers

Placement
Before you integrate the KAV-250aor KAV-250a/3into your system, review the
following guidelinesto choosethe location for the component.Thiswill facilitate a
clean,trouble-freeinstallation.
TheKAV-250aandKAV-250aJ3require at least two inches (5 cm)of clearance
eachside andat least twoinches(5 cm)of clearanceabovethe componentto provide
adequateventilation.
Youramplifier doesnot requireanytype of special rackor cabinetfor installation. For
the dimensionsof your amplifier seeSpecifications, on pages30 and31.
Placethe amplifier as close to the loudspeakersas possible andkeepthe speaker
cable length to a minimum.Speakercable addsimpedanceto the load the amplifier
mustdrive, regardlessof the cable’s gauge.Krell amplifiers drive the lowest
impedanceswith ease, but long speakercables reducethe maximumpowerthat is
deliveredto the loudspeakers.
AC POWER GUIDELINES
Krell recommendsoperating eachamplifier from a dedicated15-ampACpowerline.
For maximumpoweroutput, operate the KAV-250aor KAV-250a/3amplifier from a
dedicated 20-ampACpowerline.
KAV-250aand KAV-250a/3Amplifiers 3

FIGURE 1 THE KAV-250a FRONTPANEL
1 2
1 PowerButton
2 PowerLED

Front Panel Description: KAV-250a
SeeFigure 1 on page4
1 Power Button
Usethis button to turn the KAV-250apoweron andoff andalso to switch the 12 VDC
output(12Vtrigger) onandoff.
2 Power LED
Theblue powerLEDilluminates whenthe amplifier is on.
KAV-250aand KAV-250a/3Amplifiers 5

FIGURE 2 THE KAV-250a BA(;K PANEL
5
11 12 10 13
BalancedInputs
3 Right Input
4 Left Input (Bridged)
Single-endedInputs
5 Right Input
6 Left Input (Bridged)
Amplifier ChannelOutputs
7 Right Output(Bridged-)
8 Left Output(Bridged+)
Fuses
9 AGC~ Fuses
10 Line Fuse
RemoteControls
11 12 VDCRemotePowerOut
12 12 VDCRemotePowerIn
Power
13 IEC PowerConnector

BackPanel Description: KAV-250a
SeeFigure 2 on page6
TheKAV-250abackpanel provides connectionsfor all inputs andoutputs, remote
control input andoutput links, andACpowersupply. Inputs andoutputslabeled left and
right areonthe left andright sideof theamplifier, respectively,whenviewingthe
amplifier fromthe front panel.
Balanced Inputs
3, 4 Inputs
Theseare the right (3) andthe left (4) KAV-250achannelinputs for output devices
balancedXLRconnectors.
Single-ended Inputs
5,6 Inputs
Theseare the right (5) andthe left (6) KAV-250achannelinputs for outputdevices
single-ended RCAconnectors.
Theleft balancedor single-endedinputs are usedfor bridgedoperation. See
Reconfiguring the KAV-250afor BridgedOperation,on page20.
Amplifier Channel Outputs
7 OutputBridged(-)
8 Output Bridged(+)
Theseare the right (7) andleft (8) KAV-250aamplifier channeloutputswith five-way
loudspeakerbinding posts. Theloudspeakerbinding post terminals acceptspadelugs,
barewire, bananaplugs, or pins. Usethe red terminal for the positive connectionand
the black terminal for the.negativeconnection.For information on loudspeaker
connectionsfor bridged operation, see Reconfiguringthe lEA V-250afor Bridged
Operation,on page20.
Fuses
9 AGC-12Fuses
TheAGC12 Volt loudspeakerfuses protect the KAV-250aagainst short circuits in
loudspeakeroutput.
10 Line Fuse
Theline fuseprotects the KAV-250aagainstshort circuits in internal powersupplies.
Note
Fusesmustbe replacedwith the fuse value specified on the KAV-250abackpanel. Use
a 20 ampslow-blowline fuse for 100/120V systemsor a 12 ampslow-blowline fuse for
220/240 V systems.
KAV-250aandKAV-250a/3Amplifiers 7

BackPanelDescription,continued
RemoteControls
11 12 VDCRemotePowerOut
12 12 VDCRemotePowerIn
TheKAV-250ais equippedwith an output that sends12 VDCpoweron/off (12
trigger) signals to other Krell componentsandother devicesthat incorporate
12 Vtrigger. Thisallows youto turn the KAV-250aonandoff usinga Krell or other
componentin a custominstallation.
Notes
12VDCOut/in (12 V trigger) remotepoweris limited to 30ma.
Consultthe owner’smanualof anycomponentusedin a custominstallation to take full
advantageof the KAV-250aremotecapability.
PowerSupply
13 IEC Connector
TheKAV-250ais equippedwith a standardfemaleIECpowerconnector, for use with
the provided ACpowercord,
8KAV-250aand KAV-250a/3Amplifiers

FIGURE3 THE KAV-250a/3 FRONTPANEL
1415
14 PowerButton
15 PowerLED

Front Panel Description: KAV-250a/3
SeeFigure 3 on page9
14 PowerButton
Usethis button to turn the KAV-250a/3poweron andoff andalso to switch the 12 VDC
output(12Vtrigger) onandoff.
15 Power LED
Theblue powerLEDilluminates whenthe amplifier is poweredon.
10 KAV-250aand KAV-250a/3Amplifiers

FIGURE 4 THE KAV-250a/3 BACK PANEL
16 19 17 2o 18 21
25 22 25 23 25 24 27 28 26 29
BalancedInputs
16Right Input
17CenterInput
18 Left Input
Single-endedInputs
19 Right Input
20 CenterInput
21Left Input
Amplifier ChannelOutputs
22 Right Output
23 Center Output
24 Left Output
Fuses
25 AGCe~Euses ~-----’~
26 Line Fuse
RemoteControls
27 12 VDCRemotePowerOut
28 12 VDCRemotePowertn
Power
29 IEC PowerConnector
ZOO0.

BackPanel Description: KAV-250a/3
SeeFigure 4 on page11
TheKAV-250a/3backpanel provides connectionsfor all inputs andoutputs, remote
control input andoutput links, andACpowersupply. Inputs andoutputslabeledleft and
right are ontheleft andright side of the amplifier, respectively,whenviewingthe
amplifier fromthefront panel.
Balanced Inputs
16, 17, 18 Inputs
Theseare the right (16), center (17), andleft (18) KAV-250a/3channe~inputs
output devices with balancedXLRconnectors.
Single-ended Inputs
19, 20, 21 Inputs
Theseare the right (19), center (20), andleft (21) KAV-250a/3channelinputs
output deviceswith single-endedRCAconnectors.
Amplifier Channel Outputs
22, 23, 24 Outputs
Theseare the right (22), center (23), andleft (24) KAV-250a/3amplifier channel
outputs with five-way loudspeakerbinding posts. Theloudspeakerbinding post
terminalsacceptspadelugs, barewire, bananaplugs, or pins. Usethe red terminal for
the positive connectionandthe blackterminal for the negativeconnection.For
information aboutloudspeakerconnectionsfor bridged operation, see Reconfiguring
the KAV-250aJ’3for BridgedOperation,on page21.
Fuses
25 AGC-12Fuses
TheAGC12 Volt loudspeakerfuses protect the KAV-250a/3against short circuits in
loudspeakeroutput.
26 Line Fuse
Theline fuse protects the KAV-250a/3againstshort circuits in internal powersupplies.
12 KAV-250aand KAV-250aJ3Amplifiers

BackPanelDescription,continued
Note
Fusesmustbe replacedwith the fuse value specified on the KAV-250a/3backpanel
Usea 20 ampslow-blowline fuse for 100/120V systemsor a 12 ampslow-blowline
fuse for 220/240V systems.
RemoteControls
27 12 VDCRemotePower Out
28 12 VDCRemotePowerIn
TheKAV-250a/3is equippedwith an output that sends12 VDCpoweron/off (12
trigger) signals to other Krell componentsandother devicesthat incorporate
12Vtrigger. Thisallows youto turn the KAV-250aJ3onandoff usinga Krell or other
componentin a custominstallation.
Notes
12VDCOut/In (12 Vtrigger) remotepoweris limited to 30 ma.
Consultthe owner’smanualof eachcomponentusedin a custominstallation to take full
advantageof the KAV-250a/3remotecapability.
PowerSupply
29 IEC PowerConnector
TheKAV-250a/3is equippedwith a standard femaleIECpowerconnector, for use with
the provided ACpowercord.
KAV-250aand KAV-250a/3Amplifiers 13

Connectingthe KAV-250aor KAV-250a/3
Amplifier to YourSystem
INPUT AND OUTPUT CONNECTIONS
Thefollowing steps describe howto connectcables to the KAV-250aor KAV-250a/3
amplifier.
1. Neatlyarrangeandorganizethe wiring to andfromthe amplifier andall
components.SeparateACwires from audio cables to prevent humor other
unwantednoise from being introducedinto the system.
21 Connectthe loudspeakercables to the KAV-250aamplifier channeloutput speaker
binding posts(7, 8), or the KAV-250a/3amplifier channeloutput speakerbinding
posts(22, 23, 24) locatedontheir respectivebackpanels.
Theamplifier channeloutputs for the KAV-250aandKAV-250a/3use five-way
loudspeakerbinding posts. Theloudspeakerbinding post terminals accept spade
lugs, barewire, bananaplugs, or pins. Usethe red terminalfor the positive
connectionandthe black terminal for the negativeconnection.
3. Connectthe interconnectcablesfromyour output deviceto the amplifier inputs. The
KAV-250ais equippedwith balanced(3, 4) or single-ended(5, 6) inputs and
KAV-250a/3is equippedwith balanced(16, 17, 18) or single-ended(19, 20,
inputs locatedon their respectivebackpanels.Thebalancedinputs usethree-pin
XLRconnectors; the single-endedinputs use RCAconnectors.
4. Insert the endof the ACpowercord into the IECpowerconnectoron the KAV-250a
(13) or KAV-250a/3(29) backpanel.Insert the other endinto the ACwall outlet.
Theamplifier is nowreadyfor operation. SeeAmplifier Operation,on page25.
TheKAV-250aor KAV-250a/3amplifier is shippedwith shorting pins in the XLR
inputs. Thesepins shouldremainin the XLRinputs if the amplifier is operatingin the
single-endedmode.Whenthe shorting pin is inserted, pins 1 and3 are shorted
together. Removethe shorting pins to connectthe amplifier for balancedoperation.
TheXLRpin configuration is describedbelow:
Pin1 Ground
Pin 2 Non-inverting(0
°)
Pin 3 Inverting (180
°)
Krell recommendsusing balancedinterconnect cables. Balancedinterconnect cables
not only canminimizesonic loss but are also immuneto inducednoise, especially with
installations usinglong cables. Balancedconnectionshave6 dBmoregain than single-
endedconnections.Whenlevel matchingis critical, keepthis gainvaluein mind.
14 KAV-250aand KAV-250aJ3Amplifiers

Optional SystemConfigurations
TheKAV-250aand KAV-250a/3can be reconfigured for either Multi AmpThroughput
(MAT)or bridgedoperation.
IMPORTANT
Removingthe coverto reconfigurefor MAT or for bridgedoperationis the ONLY
instance youare authorized to removethe cover of ANYKre// componentwithout
voiding your Warranty.Formoreinformation onproduct/imitations andrestrictions, see
Warranty, on page28.
Before Reconfiguringfor MATor BridgedOperation
Readthe following importantsafety instructions beforeyouattemptto reconfigureyour
amplifier for either MATor bridgedoperation:
1. Unplugthe powercord. Unplugthe ACpowercord from both the IECpower
connectorof the KAV-250a(13) or KAV-250aJ3(29) on the backpanel, and
the ACoutlet.
2. Avoidthe powersupply.After removingthe screws(see instructions below) and
the cover, locate andstay awareof the location of the powersupply. Avoidmaking
contactwith that areaof the amplifier.
3. Removejewelry. Rings, necklaces,bracelets, andother piecesof metal jewelry
can conductan electrical charge. Considerremovingthembefore attempting any
reconfiguration.
4. Alwaysreplacecover.Makesure the amplifier’s cover is properly replacedand
securedby the 12 screwsbefore resumingoperation.
IMPORTANT
Operatingthe amplifier without the coverproperly replacedandsecuredmay
void your warranty.
MULTI AMP THROUGHPUT
Multi AmpThroughput(MAT),an internal connectionoption for either the KAV-250a
the KAV-250a/3,lets yousendthe samemusicsignal to all amplifier channelsusing
onebalancedor single-endedconnection. MATreducesinstallation complexity and
cabling requirementsin systemscontainingmultiple amplifiers.
Inputsandoutputslabeledleft andright are ontheleft andright sideof the amplifier,
respectively, whenviewingthe amplifier fromthe front panel
KAV-250aand KAV-250a/3Amplifiers 15

FIGURE5 RECONFIGURINGTHEKAV-250a FORMATORBRIDGEDOPERATI( tN
PCboards showing
MATjumper
configuration
Left Right
PCboards showing
bridged jumper
configuration
Left Right
Powersupply
PCboards
Right
16 KAV-250aandKAV-250-a/3Amplifiers