Krell Industries Three-Channel Power Amplifier KAV-250a/3, KAV-250a Instructions For Use Manual

Leader in Audio Engineering

KAV-250a

Stereo Power Amplifier

KAV-250a/3

Three-Channel Power Amplifier

Instructions for Use, v 99.2

Owner’s Reference

KAV-250a Stereo Power Amplifier and
KAV-250a/3 Three-Channel Power Amplifier
Instructions for Use, v 99.2

Cover: KAV-250a/3 Three-Channel Power Amplifier

Krell Industries, Inc.

45 Connair Road

Orange, CT 06477-3650 USA

TEL [phone]

FAX [phone]
E-MAIL krell @ krellonline.com

WEBSITE http://www.krellonline.com

This product complies with the EMC directive (89/336/EEC) and the low-voltage directive

(73/23/EEC).

WARNINGS

The amplifier must be placed on a firm, level surface where it is not exposed to dripping or

splashing.

The ventilation grids on the top of the amplifier and the space underneath the amplifier must be
unobstructed at all times during operation. Do not place flammable material above or beneath

the amplifier.
Contact your authorized Krell dealer, distributor, or Krell before using any devices designed to

alter or stabilize the AC power for the KA V-250a or KA V-250a/3.
Before connecting the KA V-250a or KA V-250a/3, make sure the amplifier is off and any output

device (such as a preamplifier) is in mute or stand-by mode. Make sure all cable terminations

are of the highest quality and free from frayed ends, short circuits, or cold solder joints.

Use only one set of inputs to the amplifier at a time.
After reconfiguring for MAT, do not use more than one input at the same time.
After bridging, do not use both inputs at the same time.

THERE ARE NO USER SERVICEABLE PARTS INSIDE ANY KRELL PRODUCT

Please contact your authorized Krell dealer, distributor, or Krell if you have any questions not
addressed in this reference manual.

This product is manufactured in the United States of America. Krell® is a registered trademark of Krell

Industries, Inc., and is restricted for use by Krell Industries, Inc., its subsidiaries, and authorized agents.
Multi Amp Throughput

TM

is a trademark of Krell Industries, Inc. All other trademarks and tradenames are

registered to their respective companies.

© 1999 by Krell Industries, Inc. All rights reserved P/N: I960101710688

Contents

INTRODUCTION ’
DEFINITION OF TERMS
UNPACKING
PLACEMENT

AC Power Guidelines
FRONT PANEL DESCRIPTION: KAV-250a
BACK PANEL DESCRIPTION: KAV-250a
FRONT PANEL DESCRIPTION: KAV-250a/3

BACK PANEL DESCRIPTION: KAV-250a/3

CONNECTING THE KAV-250a or KAV-250aJ3 AMPLIFIER

TO YOUR SYSTEM

Input and Output Connections

OPTIONAL SYSTEM CONFIGURATIONS

Multi Amp Throughput

Bridged Operation

Examples of Connection Scenarios

AMPLIFIER OPERATION

On/Off and Operation

AMPLIFIER TROUBLESHOOTING

How to Troubleshoot System Noise

QUESTION AND ANSWER
WARRANTY
RETURN AUTHORIZATION PROCEDURE
SPECIFICATIONS

Page

1
1

2

3
3

5
7

10

12

14
14

15

15
20
22

25
25
26
26

27

28
29
30

KAV-250a and KAV-250a/3 Amplifiers iii

Illustrations

FIGURE 1
FIGURE 2
FIGURE 3
FIGURE 4

FIGURE 5

The KAV-250a Front Panel
The KAV-250a Back Panel
The KAV-250a/3 Front Panel
The KAV-250a/3 Back Panel

Reconfiguring the KAV-250a for MAT

or Bridged Operation
FIGURE 6 Reconfiguring the KAV-250a/3 for MAT

or Bridged Operation

Page

4

6
9

11

16

19

iv KAV-250a and KAV-250a/3 Amplifiers

Introduction

Thank you for your purchase of the Krell KAV-250a Stereo Power Amplifier or

KAV-250a/3 Three-Channel Power Amplifier..

The KAV-250a and KAV-250aJ3 amplifiers provide substantial two- and three-channel
output power that delivers realistic music production at an exceptional value. These

amplifiers can be customized with a variety of optional system configurations: Multi
Amp Throughput (MAT), bridged operation, and high power mono operation. These
options provide a wider range of power outputs and connection options. Both the KAV-

250a and KAV-250a/3 amplifiers provide balanced and single-ended inputs for
complete compatibility with other components. The KAV-250a and KAV-250a/3

amplifiers can be operated using the 12 VDC trigger for other components. Either
amplifier integrates seamlessly home theater or whole-house systems.

This reference manual contains important information on placement, installation, and
operation of the KAV-250a and KAV-250a/3 amplifiers. Please read this information

carefully. A thorough understanding of these details helps ensure satisfactory operation
and long life for your KAV-250a or KAV-250aJ3 amplifier and related system

components.

Definition of Terms

Multi Amp Throughput

An internal connection option that sends the same music signal to all amplifier channels

using one balanced or single-ended connection. MAT reduces installation complexity
and cabling requirements in systems containing multiple amplifiers. MAT also allows a

variety of connection scenarios, including powering loudspeakers that have two sets of

binding posts and independently powering multiple pairs of stereo loudspeakers to
extend the listening environment throughout your home.

Bridging

An internal connection option that links two amplifier channels to operate as one
combined amplifier channel, greatly increasing the channel’s power output.

On

When the power button on the front panel is pressed and the blue power LED

illuminates, the amplifier is on and ready to play music.

Off

When the power button on the front panel is pressed and the blue power LED turns off,
the amplifier is off.

KAV-250a and KAV-250a/3 Amplifiers 1

Unpacking

Open the shipping box, which contains:

1 amplifier unit (packed in foam end-caps)

2 ribbon connection cables

KAV-250a fuses:

2 AGC-8 (~ ’amp)

1 slow-blow (20 amp for 100/120 V or 12 amp for 220/240 V)
or

KAV-250a/3 fuses:

3 AGC-.8 ~ amp)

1 slow-blow (20 amp for 100/120 V or 12 amp for 220/240 V)

1 12 VDC output (12 V trigger) cable
1 IEC connector (AC power) cord

1 T-15 Torx wrench
1 packet containing the owner’s reference manual and the warranty registration

card.

Grasp the underside of the foam end-caps that encase the amplifier and lift the

amplifier straight out of the shipping box.

Place the amplifier in a safe location and remove the protective plastic wrapping.

Notes

If any of these items are not included in the shipping box, please contact your
authorized Krell dealer, distributor, or Krell for assistance.

Save all packing materials. If you ship your amplifier in the future, repack the unit in its
original packaging to prevent trans# damage. See Return Authorization Procedure,
on page 29, for more information.

2

KAV-250a and KAV-250aJ3 Amplifiers

Placement

Before you integrate the KAV-250a or KAV-250a/3 into your system, review the

following guidelines to choose the location for the component. This will facilitate a

clean, trouble-free installation.

The KAV-250a and KAV-250aJ3 require at least two inches (5 cm) of clearance

each side and at least two inches (5 cm) of clearance above the component to provide
adequate ventilation.

Your amplifier does not require any type of special rack or cabinet for installation. For
the dimensions of your amplifier see Specifications, on pages 30 and 31.

Place the amplifier as close to the loudspeakers as possible and keep the speaker
cable length to a minimum. Speaker cable adds impedance to the load the amplifier
must drive, regardless of the cable’s gauge. Krell amplifiers drive the lowest

impedances with ease, but long speaker cables reduce the maximum power that is
delivered to the loudspeakers.

AC POWER GUIDELINES

Krell recommends operating each amplifier from a dedicated 15-amp AC power line.
For maximum power output, operate the KAV-250a or KAV-250a/3 amplifier from a

dedicated 20-amp AC power line.

KAV-250a and KAV-250a/3 Amplifiers

3

FIGURE 1 THE KAV-250a FRONT PANEL

1 2

1 Power Button

2 Power LED

Front Panel Description: KAV-250a

See Figure 1 on page 4

1 Power Button
Use this button to turn the KAV-250a power on and off and also to switch the 12 VDC

output (12 V trigger) on and off.
2 Power LED

The blue power LED illuminates when the amplifier is on.

KAV-250a and KAV-250a/3 Amplifiers 5

FIGURE 2 THE KAV-250a BA(;K PANEL

5

11 12 10 13

Balanced Inputs

3 Right Input
4 Left Input (Bridged)

Single-ended Inputs

5 Right Input
6 Left Input (Bridged)

Amplifier Channel Outputs

7 Right Output (Bridged-)
8 Left Output (Bridged+)

Fuses

9 AGC~ Fuses

10 Line Fuse

Remote Controls

11 12 VDC Remote Power Out
12 12 VDC Remote Power In

Power

13 IEC Power Connector

Back Panel Description: KAV-250a

See Figure 2 on page 6

The KAV-250a back panel provides connections for all inputs and outputs, remote
control input and output links, and AC power supply. Inputs and outputs labeled left and

right are on the left and right side of the amplifier, respectively, when viewing the

amplifier from the front panel.

Balanced Inputs

3, 4 Inputs

These are the right (3) and the left (4) KAV-250a channel inputs for output devices

balanced XLR connectors.

Single-ended Inputs

5,6 Inputs

These are the right (5) and the left (6) KAV-250a channel inputs for output devices
single-ended RCA connectors.

The left balanced or single-ended inputs are used for bridged operation. See

Reconfiguring the KA V-250a for Bridged Operation, on page 20.

Amplifier Channel Outputs

7 Output Bridged(-)
8 Output Bridged(+)

These are the right (7) and left (8) KAV-250a amplifier channel outputs with five-way

loudspeaker binding posts. The loudspeaker binding post terminals accept spade lugs,
bare wire, banana plugs, or pins. Use the red terminal for the positive connection and

the black terminal for the.negative connection. For information on loudspeaker
connections for bridged operation, see Reconfiguring the lEA V-250a for Bridged

Operation, on page 20.
Fuses

9 AGC-12 Fuses

The AGC 12 Volt loudspeaker fuses protect the KAV-250a against short circuits in

loudspeaker output.
10 Line Fuse

The line fuse protects the KAV-250a against short circuits in internal power supplies.

Note

Fuses must be replaced with the fuse value specified on the KA V-250a back panel. Use
a 20 amp slow-blow line fuse for 100/120 V systems or a 12 amp slow-blow line fuse for

220/240 V systems.

KAV-250a and KAV-250a/3 Amplifiers 7

Back Panel Description, continued

Remote Controls

11 12 VDC Remote Power Out
12 12 VDC Remote Power In

The KAV-250a is equipped with an output that sends 12 VDC power on/off (12
trigger) signals to other Krell components and other devices that incorporate

12 V trigger. This allows you to turn the KAV-250a on and off using a Krell or other
component in a custom installation.

Notes

12 VDC Out/in (12 V trigger) remote power is limited to 30 ma.

Consult the owner’s manual of any component used in a custom installation to take full
advantage of the KA V-250a remote capability.

Power Supply

13 IEC Connector

The KAV-250a is equipped with a standard female IEC power connector, for use with

the provided AC power cord,

8

KAV-250a and KAV-250a/3 Amplifiers

FIGURE 3

THE KAV-250a/3 FRONT PANEL

14 15

14 Power Button
15 Power LED

Front Panel Description: KAV-250a/3

See Figure 3 on page 9

14 Power Button

Use this button to turn the KAV-250a/3 power on and off and also to switch the 12 VDC

output (12 V trigger) on and off.

15 Power LED

The blue power LED illuminates when the amplifier is powered on.

10

KAV-250a and KAV-250a/3 Amplifiers

FIGURE 4

THE KAV-250a/3 BACK PANEL

16 19 17 2o

18 21

25 22

25 23 25 24

27 28 26 29

Balanced Inputs

16 Right Input
17 Center Input

18 Left Input

Single-ended Inputs

19 Right Input
20 Center Input
21 Left Input

Amplifier Channel Outputs

22 Right Output
23 Center Output
24 Left Output

Fuses

25 AGC e~Euses ~-----’~
26 Line Fuse

Remote Controls

27 12 VDC Remote Power Out
28 12 VDC Remote Power tn

Power

29 IEC Power Connector

ZOO0.

Back Panel Description: KAV-250a/3

See Figure 4 on page 11

The KAV-250a/3 back panel provides connections for all inputs and outputs, remote

control input and output links, and AC power supply. Inputs and outputs labeled left and
right are on the left and right side of the amplifier, respectively, when viewing the
amplifier from the front panel.

Balanced Inputs

16, 17, 18 Inputs

These are the right (16), center (17), and left (18) KAV-250a/3 channe~ inputs
output devices with balanced XLR connectors.

Single-ended Inputs

19, 20, 21 Inputs

These are the right (19), center (20), and left (21) KAV-250a/3 channel inputs
output devices with single-ended RCA connectors.

Amplifier Channel Outputs

22, 23, 24 Outputs

These are the right (22), center (23), and left (24) KAV-250a/3 amplifier channel
outputs with five-way loudspeaker binding posts. The loudspeaker binding post
terminals accept spade lugs, bare wire, banana plugs, or pins. Use the red terminal for
the positive connection and the black terminal for the negative connection. For
information about loudspeaker connections for bridged operation, see Reconfiguring

the KA V-250aJ’3 for Bridged Operation, on page 21.

Fuses

25 AGC-12 Fuses

The AGC 12 Volt loudspeaker fuses protect the KAV-250a/3 against short circuits in
loudspeaker output.

26 Line Fuse

The line fuse protects the KAV-250a/3 against short circuits in internal power supplies.

12

KAV-250a and KAV-250aJ3 Amplifiers

Back Panel Description, continued

Note

Fuses must be replaced with the fuse value specified on the KA V-250a/3 back panel
Use a 20 amp slow-blow line fuse for 100/120 V systems or a 12 amp slow-blow line
fuse for 220/240 V systems.

Remote Controls

27 12 VDC Remote Power Out
28 12 VDC Remote Power In

The KAV-250a/3 is equipped with an output that sends 12 VDC power on/off (12
trigger) signals to other Krell components and other devices that incorporate

12 V trigger. This allows you to turn the KAV-250aJ3 on and off using a Krell or other

component in a custom installation.

Notes

12 VDC Out/In (12 V trigger) remote power is limited to 30 ma.

Consult the owner’s manual of each component used in a custom installation to take full

advantage of the KA V-250a/3 remote capability.

Power Supply

29 IEC Power Connector

The KAV-250a/3 is equipped with a standard female IEC power connector, for use with
the provided AC power cord.

KAV-250a and KAV-250a/3 Amplifiers 13

Connecting the KAV-250a or KAV-250a/3

Amplifier to Your System

INPUT AND OUTPUT CONNECTIONS

The following steps describe how to connect cables to the KAV-250a or KAV-250a/3
amplifier.

1. Neatly arrange and organize the wiring to and from the amplifier and all
components. Separate AC wires from audio cables to prevent hum or other

unwanted noise from being introduced into the system.

21 Connect the loudspeaker cables to the KAV-250a amplifier channel output speaker

binding posts (7, 8), or the KAV-250a/3 amplifier channel output speaker binding
posts (22, 23, 24) located on their respective back panels.

The amplifier channel outputs for the KAV-250a and KAV-250a/3 use five-way
loudspeaker binding posts. The loudspeaker binding post terminals accept spade

lugs, bare wire, banana plugs, or pins. Use the red terminal for the positive
connection and the black terminal for the negative connection.

3. Connect the interconnect cables from your output device to the amplifier inputs. The
KAV-250a is equipped with balanced (3, 4) or single-ended (5, 6) inputs and
KAV-250a/3 is equipped with balanced (16, 17, 18) or single-ended (19, 20,

inputs located on their respective back panels. The balanced inputs use three-pin
XLR connectors; the single-ended inputs use RCA connectors.

4. Insert the end of the AC power cord into the IEC power connector on the KAV-250a
(13) or KAV-250a/3 (29) back panel. Insert the other end into the AC wall outlet.

The amplifier is now ready for operation. See Amplifier Operation, on page 25.
The KAV-250a or KAV-250a/3 amplifier is shipped with shorting pins in the XLR

inputs. These pins should remain in the XLR inputs if the amplifier is operating in the
single-ended mode. When the shorting pin is inserted, pins 1 and 3 are shorted

together. Remove the shorting pins to connect the amplifier for balanced operation.
The XLR pin configuration is described below:

Pin 1 Ground
Pin 2 Non-inverting (0

°)

Pin 3 Inverting (180

°)

Krell recommends using balanced interconnect cables. Balanced interconnect cables
not only can minimize sonic loss but are also immune to induced noise, especially with

installations using long cables. Balanced connections have 6 dB more gain than single­ended connections. When level matching is critical, keep this gain value in mind.

14

KAV-250a and KAV-250aJ3 Amplifiers

Optional System Configurations

The KAV-250a and KAV-250a/3 can be reconfigured for either Multi Amp Throughput
(MAT) or bridged operation.

IMPORTANT

Removing the cover to reconfigure for MA T or for bridged operation is the ONL Y

instance you are authorized to remove the cover of ANY Kre// component without

voiding your Warranty. For more information on product/imitations and restrictions, see
Warranty, on page 28.

Before Reconfiguring for MAT or Bridged Operation

Read the following important safety instructions before you attempt to reconfigure your
amplifier for either MAT or bridged operation:

1. Unplug the power cord. Unplug the AC power cord from both the IEC power
connector of the KAV-250a (13) or KAV-250aJ3 (29) on the back panel, and

the AC outlet.

2. Avoid the power supply. After removing the screws (see instructions below) and
the cover, locate and stay aware of the location of the power supply. Avoid making

contact with that area of the amplifier.

3. Remove jewelry. Rings, necklaces, bracelets, and other pieces of metal jewelry
can conduct an electrical charge. Consider removing them before attempting any

reconfiguration.

4. Always replace cover. Make sure the amplifier’s cover is properly replaced and
secured by the 12 screws before resuming operation.

IMPORTANT

Operating the amplifier without the cover properly replaced and secured may
void your warranty.

MULTI AMP THROUGHPUT

Multi Amp Throughput (MAT), an internal connection option for either the KAV-250a
the KAV-250a/3, lets you send the same music signal to all amplifier channels using

one balanced or single-ended connection. MAT reduces installation complexity and
cabling requirements in systems containing multiple amplifiers.

Inputs and outputs labeled left and right are on the left and right side of the amplifier,

respectively, when viewing the amplifier from the front panel

KAV-250a and KAV-250a/3 Amplifiers 15

FIGURE 5 RECONFIGURING THE KAV-250a FOR MAT OR BRIDGED OPERATI( tN

PC boards showing
MAT jumper

configuration

Left Right

PC boards showing
bridged jumper

configuration

Left

Right

Power supply

PC boards

Right

16 KAV-250a and KAV-250-a/3 Amplifiers

Reconfiguring the KAV-250a for MAT

See Figure 5 on page 16

Tools needed: T-15 Torx wrench and one ribbon connection cable

1. Turn the KAV-250a off by pressing the power button (1) on the front panel. The blue
power LED (2) extinguishes. Unplug the AC power cord from the IEC power

connector (13) on the back panel.

2. Using the T:15 Torx wrench, remove the 12 screws that secure the amplifier cover.
Carefully remove the cover.

3.

Locate the small PC board at the rear of each amplifier channel and jumper pins
labeled J4, J5, and J6.

4.

Connect one end of the ribbon connection cable to jumper pin J4 on the left
amplifier channel (closest to the power supply). The ribbon snaps into place.

Connect the other end of the ribbon connection cable to jumper pin J5 on the right
amplifier channel.

5.

Replace the cover (slide the front panel end in first). Using the T-15 Torx wrench,
secure the 12 screws.

The KAV-250a amplifier is now reconfigured for MAT operation.

Connecting the KAV-250a Reconfigured for MAT

See Figure 2 on page 6

1. Connect your output device to a single-ended or balanced input on the back panel of
the KAV-250a.

2. Connect each amplifier channel output (7, 8) to a separate loudspeaker, using the
positive and negative terminals on the speaker binding posts.

Reconfiguring the KAV-250a/3 for MAT

See Figure 6 on page 19

Tools needed: T-15 Torx wrench and two ribbon connection cables

1. Turn the KAV-250a/3 off by pressing the power button (14) on the front panel. The
blue power LED (15) extinguishes. Unplug the AC power cord from the IEC power

connector (29) on the back panel.

2. Using the T-15 Torx wrench, remove the 12 screws that secure the amplifier cover.
Carefully remove the cover.

3.

Locate the small PC board at the rear of each amplifier channel and jumper pins
labeled J4, J5, and J6.

4. Connect one end of the first ribbon connection cable to jumper pin J4 on the left
amplifier channel (closest to the power supply). The ribbon snaps into place.
Connect the other end of this ribbon connection cable to jumper pin J5 on the center

amplifier channel.

KAV-250a and KAV-250a/3 Amplifiers 17

5. Connect one end of the second ribbon connection cable to jumper pin J4 on the
center amplifier channel. Connect the other end of this ribbon connection cable to

jumper pin J5 on the right amplifier channel.

6.

Replace the cover (slide the front panel end in first). Using the T-15 Torx wrench,
secure the 12 screws.

The KAV-250a/3 amplifier is now reconfigured for MAT operation.

Connecting the KAV-250a/3 Reconfigured for MAT

See Figure 4 on page 11

1. Connect your output device to a single-ended or balanced input on the back panel of
the KAV-250a/3.

2. Connect each amplifier channel output (22, 23, 24) to a separate loudspeaker, using
the positive and negative terminals on the speaker binding posts.

18

KAV-250a and KAV-250a/3 Amplifiers

FIGURE 6 RECONFIGURING THE KAV-250a/3 FOR MAT OR BRIDGED OPERATION

PC boards showing

MAT jumper
configuration

PC boards showing
bridged jumper

configuration

(See Option 1,

on page 21)
PC boards showing

bridged jumper

configuration

(See Option 2,

on page 21)

Left Center Right

Power supply

PC boards

ht

KAV-250a and KAV-250-a/3 Amplifiers

19

BRIDGED OPERATION

The KAV-250a and the KAV-250a/3 can be reconfigured for bridged operation. When
the KAV-250a amplifier’s channels are bridged, the amplifier’s output power is

quadrupled: the amplifier delivers 1,000 Watts to an 8 Ohm load. The KAV-250a/3 can
be reconfigured to bridge any two of its three amplifier channels to operate as one
combined amplifier channel. When using the bridged amplifier channel only, the
KAV-250a/3 delivers 1,000 Watts to an 8 Ohm load.

Inputs and outputs labeled left and right are on the left and right side of the amplifier,
respectively, when viewing the amplifier from the front panel

Reconfiguring the KAV-250a for Bridged Operation

See Figure 5 on page 16

Tools needed: T-15 Torx wrench and one ribbon connection cable

1.

Turn the KAV-250a off by pressing the power button (1) on the front panel. The blue

power LED (2) extinguishes. Unplug the AC power cord from the IEC power
connector (13) on the back panel.

2. Using the T-15 Torx wrench, remove the 12 screws that secure the amplifier cover.
Carefully remove the cover.

3.

Locate the small PC board at the rear of each amplifier channel and jumper pins
labeled J4, J5, and J6.

4.

Connect one end of the ribbon connection cable to jumper pin J4 on the left

amplifier channel (closest to the power supply). The cable snaps into place. Connect
the other end of the ribbon connection cable to jumper pin J6 on the right amplifier

channel.

5.

Replace cover (slide front panel end in first). Using the T-15 Torx wrench, secure

the 12 screws.

The KAV-250a amplifier is now ready for bridged operation.

Connecting the Bridged KAV-250a

See Figure 2 on page 6

1. Connect the output cable from the output device to the balanced XLR (4/ or the
single-ended RCA (6) inputs connectors marked (BRIDGED ~NPUT).

2. Connect the positive loudspeaker lead (red) to the positive binding post on the left
amplifier channel output (8), marked BRIDGED (+). Connect the negative loudspeaker

lead (black) to the positive binding post on the right amplifier channel (7), marked
BRIDGED (-).

20

KAV-250a and KAV-250a/3 Amplifiers

IMPORTANT

When operating the amplifier in bridged mode and using an output device with
single-ended RCA cables, be sure to remove the shorting pin from the/eft balanced
XLR input (4).

Reconfiguring the KAV-250a/3 for Bridged Operation

See Figure 6 on page 19

Tools needed: T-15 Torx wrench and two ribbon connection cables

1. Turn the KAV-250a/3 off by pressing the power button (14) on the front panel. The
blue power LED (15) extinguishes. Unplug the AC power cord from the IEC power

connector (29) on the back panel.

2. Using the T-15 Torx wrench, remove the 12 screws that secure the amplifier cover.
Carefully remove the cover.

3.

Locate the small PC board at the rear of each amplifier channel and jumper pins
labeled J4, J5, and J6.

4.

Option 1: To bridge left and center amplifier channels, connect one end of the
ribbon connection cable to jumper pin J4 on the left amplifier channel (closest to the
power supply). The cable snaps into place. Connect the other end of the ribbon

connection cable to jumper pin J6 on the center amplifier channel.

Option 2: To bridge center and right amplifier channels, connect one end of the
ribbon connection cable to jumper pin J4 on the center amplifier channel. Connect

the other end of the ribbon connection cable to jumper pin J6 on the right amplifier
channel.

5.

Replace cover (slide the front panel end in first). Using the T-15 Torx wrench,

secure the 12 screws.

The KAV-250aJ3 amplifier is now ready for bridged operation.

Connecting the Bridged KAV-250a/3

See Figure 4 on page 11

1.

When the left and center amplifier channels are bridged (Option 1), connect the

output cable from the output device to the center balanced XLR (17) or single-ended

RCA (20) input.

Connect the positive loudspeaker lead (red) to the positive binding post on the
center amplifier channel (23). Connect the negative loudspeaker lead (black) to

positive binding post of the left amplifier channel (24).

KAV-250a and KAV-250a/3 Amplifiers 21

2. When the center and right amplifier channels are bridged (Option 2), connect the
output cable from the output device to the right balanced XLR (16) or single-ended

RCA (19)input.
Connect the positive loudspeaker lead (red) to the positive binding post on the

(right) amplifier channel (22). Connect the negative loudspeaker lead (black)
positive binding post of the center amplifier channel (23).

The remaining channel may be connected for normal operation.

IMPORTANT

When operating the amplifier in bridged mode and using an output device with a

single-ended RCA cable, be sure to remove the shorting pin from the balanced XLR

input.

EXAMPLES OF CONNECTION SCENARIOS

High Power Mono Operation

High power mono operation uses two KAV-250a bridged amplifiers: one amplifier is
dedicated to the left loudspeaker and one amplifier is dedicated to the right

loudspeaker. Additional loudspeakers in a home theater system may be connected in

this way by using additional KAV-250a amplifiers. The diagram below illustrates
connecting a system for high power mono operation:

22

KAV-250a and KAV-250a/3 Amplifiers

Examples of Connection Scenarios, continued

Power Biamplification (Stereo, 2-channel)

Power biamplification uses the MAT feature of the KAV-250a to send the same music
signal to all amplifier channels using one balanced or single-ended input connection.

When the KAV-250a is reconfigured for MAT, one channel of the amplifier powers the

Ioudspeaker’s high frequency end, and the other channel powers the Ioudspeaker’s low
frequency end. This connection scenario is used only with loudspeakers that feature
two sets of binding posts. For more information, consult the owner’s reference for your

loudspeakers. The diagram below illustrates connecting a system for power
biamplification:

KAV-250a and KAV-250aJ’3 Amplifiers

23

Examples of Connection Scenarios, continued

Multi Power Mode

Multi power mode uses the KAV-250a/3’s MAT feature to independently power multiple
pairs of stereo loudspeakers to extend the listening environment throughout your home.

When the KAV-250a/3 is reconfigured for MAT, each channel powers an individual

loudspeaker, with one KAV-250a/3 dedicated to driving outputs to the left loudspeakers

and one KAV-250a/3 driving outputs to the right loudspeakers. The diagram below
illustrates connecting a system for multi power mode:

24 KAV-250a and KAV-250aJ3 Amplifiers

Amplifier Operation

ON/OFF AND OPERATION

When powering up your system, turn amplifiers on last. When powering down your
system, turn amplifiers off first. The procedures for amplifier operation follow.

1. Press the KAV-250a power button (1) or KAV-250a/3 power button (14) on
amplifier’s front panel. Wait until the blue power LED (2) on the KAV-250a or (15)

on the KAV-250a/3 illuminates and you hear a click. The amplifier is now ready for

operation.

2. With the output device muted or volume control fully lowered, select an output
device. Decrease or increase the volume control to the desired listening level.

3. Before turning the system off, mute or lower the output device volume. Press the
front panel power button to turn the amplifier off. It is now safe to turn off the rest of

the system.

IMPORTANT

Always turn off the amplifier before changing input connections, and mute or fully
attenuate the preamplifier level when switching sources.

These amplifiers have tremendous reserves of power and safely drive loudspeakers to

extremely high sound pressure levels. However, use care when setting high playback
levels and lower the volume level at any sign of loudspeaker distress.

KAV-250a and KAV-250a/3 Amplifiers

25

Amplifier Troubleshooting

HOW TO TROUBLESHOOT SYSTEM NOISE

When you mix and match audio components, each with its own ground potential, a low
frequency hum may occur in one or both loudspeakers. This often occurs when

introducing a new component into a system.
If a low frequency hum emanates from the loudspeakers when you place the KAV-

250a stereo or KAV-250a/3 three-channel amplifier into your system, follow these
simple troubleshooting steps.

1,

Check all input and output connections, making sure they are of sound construction.

2. With the amplifier off, remove the interconnect cables, then press the KAV-250a
power button (1) or KAV-250a/3 power button (14) to turn the amplifier

3.

If the hum disappears, press the power button again to turn the amplifier off and
reinsert one of the interconnect cables.

4.

Turn the amplifier back on. If the hum reappears with one or both interconnect
cables inserted, there may be a defective cable. Have the interconnect cables
checked before proceeding.

If the interconnect cables are sound, you may be experiencing a ground loop. This can
often be easily eliminated. Please contact your authorized Krell dealer, distributor, or

Krell for suggestions on how to solve this problem.

26

KAV-250a and KAV-250a/3 Amplifiers

Question and Answer

Q. Should I leave the KAV-250a or KAV-250a/3 amplifier on at all times?
A. No. These amplifiers do not have a stand-by mode. Leaving them on at all times

would result in considerable heat output and power consumption. For best results, turn
the amplifier off when not in use, and allow a five minute warm-up after it is turned on.
See Amplifier Operation, on page 25.

Qo When I turn the amplifier on there is a loud hum through the loudspeakers. What
should I do?

A. When a new component is introduced, a low frequency hum may occur in one or
both loudspeakers. Check all input and output connections and cables, making sure

they are of sound construction. See How to Troubleshoot System Noise, on page 26.
If the connections and cables are sound, you may be experiencing a ground loop. This

can often be easily eliminated. Please contact your authorized Krell dealer, distributor,
or Krell for suggestions on how to solve this problem.

Q. When I connect the amplifier to my system using the single-ended inputs, a loud
buzz comes from my loudspeakers. Is the amplifier broken?

A. Check that the shorting pins for the KAV-250a or KAV-250a/3 are inserted into the
XLR inputs (the unit is shipped with the pins in place). When using the single-ended

inputs, these shorting pins must be inserted between pins 1 and 3 to keep external
noise from corrupting the signal. For more information, see Connecting the KAV-250a
or KA V-250a/3 Amplifier to Your System, on page 14.

KAV-250a and KAV-250a/3 Am plifiers 27

Warranty

The KAV-250a and KAV-250a/3 amplifiers have. a limited
and transferable warranty of five years for parts and labor

on cimuitry. Should this product fail to perform at any time
during the warranty, Krell will repair it at no cost to the
owner, except as set forth in this warranty.

This warranty does not apply to damage caused by acts of
God or nature.

The warranty described on this page shall be in lieu of any
other warranty, expressed or implied, including, but not lim­ited to, any implied warranty of merchantability or fitness for

a particular purpose. There are no warranties which exceed
beyond those described in this document. If this product
does not perform as warranted herein, the owner’s sole

remedy shall be repair. In no event will Krell be liable for inci­dental or consequential damages arising from purchase,

use, or inability to use this product, even if Krell has been
advised of the possibility of such damages.

The warranty pedod begins on the date of retail purchase,

as noted on the retail sales slip provided by an authorized
Krell dealer or distributor, or on the warranty registration

card sent to Krell. In the event adequate proof of purchase
date is unavailable, the warranty pedod will begin on the

date the unit was originally shipped from the factory. Krell

can determine the original ship date from the serial number.
Transfer of warranty to a second owner occurs auto-

matically. Please contact Krell to have the registration on the

warranty changed. When the warranty is transferred, any
successive owner assumes the remainder of the odginal

warranty period.
The warranty for Krell products is valid only in the country to

which they were originally shipped, through the authorized

Krell distributor for that country, and at the factory. There

may be restrictions on or changes to Krell’s warranty
because of regulations within a specific country. Please

check with your distributor for a complete understanding of
the warranty in your country.

If a unit is serviced by a distributor who did not import the

unit, there may be a charge for service, even if the product
is within the warranty period.

Freight to the factory is your responsibility. Return freight
within the United States (U.S.A.) is included in the warranty.

If you have purchased your Krell product outside the U.S.A.
and wish to have it serviced at the factory, all freight and
associated charges to the factory are your responsibility.

Krell will pay return freight to the U.S.A.-based freight for­warder of your choice. Freight and other charges to ship the

unit from the freight forwarder to you are also your respon­sibility.

Krell is not responsible for any damage incurred in transit.

Krell will file claims for damages as necessary for units dam­aged in transit to the factory. You are responsible for filing
claims for shipping damages during the return shipment.

Krell does not supply replacement parts and/or products to
the owner of the unit. Replacement parts and/or products
will be furnished only to the distribtuor performing service on

this unit on an exchange basis only; any parts and/or prod-

ucts returned to Krell for exchange become the property of

Krell.

No expressed or implied warranty is made for any Krell
product damaged by accident, abuse, misuse, natural or

personal disaster, or unauthorized modification.

Any unauthorized voltage conversion, disassembly,
component replacement, perforation of chassis,
updates, or modifications performed to the unit will

void the warranty.

The operating voltage of this unit is determined by the fac­tory and can only be changed by an authorized Krell distrib-

utor or at the factory. The voltage for this product in the
U.S.A. cannot be changed until six months from the original

purchase date.
In the event that Krel] receives a product for warranty ser-

vice that has been modified in any way without Krell autho­rization, all warranties on that product will be void. The prod-

uct will be returned to original factory layout Sl~ecifications at

the owner’s expense before it is repaired. All repairs

required after the product has been retumed to odginal fac-

tory specifications will be charged to the customer, at cur-

rent parts and labor rates.
All operational features, functions, and specifications and

policies are subject to change without notification.

To register your product for warranty benefits,
complete and return the Warranty

Registration Card enclosed in the shipping
box within 15 days of purchase. Thank you.

28 KAV-250a and KAV-250a/3 Amplifiers

Return Authorization
Procedure

If you believe there is a problem with your
component, please contact your dealer, dis-

tributor, or the Krell factory to discuss the

problem before you return the component for
repair. To expedite service, you may wish to

complete and e-mail the Service Request
Form in the Service Section of our website

at:

http://www.krellonline.com

To contact the Krell Service Department

TEL [phone]

Monday-Friday

9:00 AM to 5:00 PM EST

FAX [phone]

E-MAIL service@ krellonline.com

WEBSITE http://www.krellonline.com

PRODUCT NAME SERIAL NUMBER

To return this product to Krell, please

follow this procedure so that we may

serve you better:

1. Obtain a Return Authorization Number
(R/A number) and shipping address

from the Krell Service Department.

2.

Insure and accept all liability for loss of

or damage to this product during ship-

ment to the Krell factory and prepay all

shipping charges. Please see the
Warranty page in this manual, concern­ing liability for shipping damage and

shipping charges.

This product may also be hand delivered if
arrangements with the Service Department

have been made in advance. Proof of pur-

chase will be required for warranty valida­tion at the time of hand delivery.

IMPORTANT

Use the original packaging to ensure safe

transit of this product to the dealer, distribu­tor, or factory. Krell may, at its discretion,
return this product in new packaging and bill

the owner for such packaging if the product
received by Krell was boxed in non-stan-

dard packaging or if the original packaging
was so damaged that it was unusable. If

Krell determines that new packaging is
required, the owner will be notified before

this product is returned.

To purchase additional packaging, please
contact your authorized Krell dealer, distrib-

utor, or the Krell Service Department.

29

KAV-250a and KAV-250a/3 Amplifiers

Specifications

KAV-250a Stereo Amplifier

FREQUENCY RESPONSE

SIGNAL TO NOISE RATIO
"A" WEIGHTED

TOTAL HARMONIC DISTORTION (THD)

GAIN
INPUT IMPEDANCE

INPUT SENSITIVITY
OUTPUT VOLTAGE

OUTPUT POWER, EACH CHANNEL
DRIVEN

BRIDGED
POWER CONSUMPTION

INPUTS

OUTPUTS

DIMENSIONS

WEIGHT

20 Hz to 20 kHz +0 dB, -0.1 dB

0.4 Hz to 170 kHz +0 dB, -3 dB

118dB
1 kHz < 0.06%

20 kHz < 0.25%

26.4 dB
100 kOhms

2.15 Vrms
Peak to Peak

RMS
8 Ohms

4 Ohms
8 Ohms

Idle
Max.

138 V

49 V
250 W
500 W

1,000 W

210W

1,850 W
1 pair single-ended via RCA connectors
1 pair balanced via XLR connectors
1 pair amplifier channels via five-way speaker

binding posts

19w x 6.3h x 15.3d in.

48.3w x 16h x 38.9d cm
Shipping 50 lb., 22.7 kg

Unit only 43 lb., 19.5 kg

30

KAV-250a and KAV-250a/3 Amplifiers

KAV-250a/3 Three-Channel Amplifier

FREQUENCY RESPONSE

20 Hz to 20 kHz

0.4 Hz to 112 kHz

SIGNAL TO NOISE RATIO
"A" WEIGHTED

TOTAL HARMONIC DISTORTION (THD)

GAIN

INPUT IMPEDANCE
INPUT SENSITIVITY

OUTPUT VOLTAGE

OUTPUT POWER, EACH CHANNEL

DRIVEN
BRIDGED
POWER CONSUMPTION

INPUTS

OUTPUTS

DIMENSIONS

WEIGHT

+0 dB, -0.2 dB

+0 dB, -3 dB

118dB
1 kHz < 0.06%

20 kHz < 0.25%

26.4 dB
100 kOhms

2.15 Vrms

Peak to Peak
RMS

8 Ohms
4 Ohms

8 Ohms
Idle

Max.

138 V

49 V
250 W
500 W

1,000 W

235 W

1,930 W
3 single-ended via RCA connectors
3 balanced via XLR connectors
3 amplifier channels via five-way speaker

binding posts
19w x 6.3h x 15.8d in.

48.3w x 16h x 40.1d cm
Shipping 60 lb., 27.2 kg

Unit only 52 lb., 23.5 kg

All operational features, functions, specifications, and policies are subject to change without

notification.

KAV-250a and KAV-250a/3 Amplifiers

31

Krell Industries, Inc.
45 Connair Road

Orange, CT 06477-3650 USA
TEL [phone]

FAX [phone]
E-MAIL krell@ krellonline.com

WEBSITE http://www.krellon line.corn

KAV-250a

Stereo Power Amplifier

KAV-250a/3

Three-Channel Power Amplifier