Krell KAV 3250 User Manual

Instructions for Use

Owner’s Reference

THE LEADER IN AUDIO ENGINEERING

KAV–2250

Stereo Power Amplifier

KAV–3250

Three-channel Power Amplifier

KAV–2250
Stereo Power Amplifier

KAV–3250
Three-channel Power Amplifier

Instructions for Use

v 01.2

Krell Industries, Inc.
45 Connair Road
Orange, CT 06477-3650 USA

TEL [phone]
FAX [phone]
E-MAIL [e-mail]
WEBSITE http://www.krellonline.com

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™ and Krell Current Mode™ are trademarks of Krell Industries, Inc. All other
trademarks and tradenames are registered to their respective companies.

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 and bottom of 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 KAV–2250 and the KAV–3250.

Before connecting the KAV–2250 and the KAV–3250, make sure the amplifier is turned 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 input to each amplifier channel at a time.

Make sure that only one switch on an input switch bank is in the up (on) position at one 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.

© 2001 by Krell Industries, Inc. All rights reserved P/N 305573

Krell KAV–2250 and KAV–3250 27

Specifications

KAV–3250

FREQUENCY

20 Hz to 20 kHz +0 dB, -0.09 dB

RESPONSE

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

SIGNAL TO NOISE
RATIO

“A” WEIGHTED >112 dB

TOTAL HARMONIC

1 kHz < 0.03%

DISTORTION (THD)

20 kHz < 0.20%

GAIN

25.7 dB

INPUT IMPEDANCE

100 kOhms

INPUT SENSITIVITY

2.32 Vrms

OUTPUT VOLTAGE

Peak to Peak 127 V

RMS 45 V

OUTPUT POWER

EACH CHANNEL 8 Ohms 250 W
4 Ohms 500 W
BRIDGED 8 Ohms 1000 W

POWER

Standby 45 W

CONSUMPTION

Idle 115 W

Max. 2000 W

INPUTS

3 single-ended via RCA connectors

3 balanced via XLR connectors

OUTPUTS

3 amplifier channels via five-way binding posts

REMOTE CONNECTORS

12 VDC Out (12 V trigger) via a 3.5 mm connector

12 VDC In (12 V trigger) via a 3.5 mm connector

DIMENSIONS

17.3w x 5.6h x 17.1d in.

43.8w x 14.3h x 43.4d cm

WEIGHT

SHIPPING 78.0 lb., 35.3 kg

UNIT ONLY 68.0 lb., 30.8 kg

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

Krell KAV–2250 and KAV–3250 iii

Contents

Page

INTRODUCTION 1

DEFINITION OF TERMS 2

UNPACKING 4

PLACEMENT 5

AC Power Guidelines 5

FRONT PANEL DESCRIPTION 7

BACK PANEL DESCRIPTION 9

CONNECTING THE AMPLIFIER TO YOUR SYSTEM 11

Input and Output Connections 11

AMPLIFIER OPERATION 13

On/Off and Operation 13
Using a Dedicated Wall Switch 13

TROUBLESHOOTING SYSTEM NOISE 14

RECONFIGURATION OPTIONS FOR THE KAV–2250 AND KAV–3250 15

To Safely Access the Input Switch Banks 15
Amplifier Factory Default Settings 18
Reconfiguring the Amplifier for MAT Operation 18
Reconfiguring the Amplifier for Bridged Operation 21
Example of a Connection Scenario: Multi-power Mode 22

QUESTIONS AND ANSWERS 23

WARRANTY 24

RETURN AUTHORIZATION PROCEDURE 25

SPECIFICATIONS
KAV–2250 26
KAV–3250 27

iv

Krell KAV–2250 and KAV–3250

Illustrations

Page

FIGURE 1 The KAV–2250 Front Panel 6

FIGURE 2 The KAV–3250 Front Panel 6

FIGURE 3 The KAV–2250 Back Panel 8

FIGURE 4 The KAV–3250 Back Panel 8

FIGURE 5 Amplifier Factory Default Settings 16

FIGURE 6 Reconfiguring the KAV–2250 for MAT Operation 17

FIGURE 7 Reconfiguring the KAV–3250 for MAT Operation 17

FIGURE 8 Reconfiguring the KAV–2250 for Bridged Operation 20

FIGURE 9 Reconfiguring the KAV–3250 for Bridged Operation 20

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 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, concern-
ing 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 valida-
tion at the time of hand delivery.

IMPORTANT

Use the original packaging to ensure safe
transit of this product to the dealer, distribu-
tor, 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 unuseable. 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.

Krell KAV–2250 and KAV–3250 25

To contact the Krell Service Department

TEL [phone]

Monday-Friday
9:00 AM to 5:00 PM EST

FAX [phone]

E-MAIL [e-mail]

WEBSITE http://www.krellonline.com

PRODUCT NAME

MODEL NUMBER SERIAL NUMBER

Krell KAV–2250 and KAV–3250 1

Introduction

Thank you for your purchase of the Krell KAV–2250 Stereo Power Amplifier or the KAV–
3250 Three-channel Power Amplifier.

The KAV–2250 and KAV–3250 amplifiers provide substantial two- and three-channel
output power that delivers realistic music reproduction at an exceptional value. These
amplifiers can be customized with two optional system configurations: Multi Amp
Throughput (MAT) and bridged operation. These configurations provide a wider range of
power outputs and connection options. Both the KAV–2250 and KAV–3250 amplifiers
have balanced and single-ended inputs, for complete compatibility with other
components. The KAV–2250 and KAV–3250 amplifiers can be operated using the 12
VDC trigger on other components. Either amplifier integrates seamlessly into home
theater or whole-house systems.

This reference manual contains important information on placement, installation, and
operation of the KAV–2250 and KAV–3250 amplifiers. Please read this information
carefully. A thorough understanding of these details helps ensure satisfactory operation
and long life for your amplifier and related system components.

2

Krell KAV–2250 and KAV–3250

Definition of Terms

Following are the definitions of key terms used in your owner’s reference manual.

CONFIGURATIONS

Bridging

A method of linking two amplifier channels by distributing the speaker load between the
positive binding posts. Bridging the channels quadruples the power rating at 8 Ohms.
Bridged configurations should not be used with loads under 4 Ohms.

Krell Multi Amp Throughput (MAT)

An internal configuration 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.

INPUT AND OUTPUT CONNECTIONS

Balanced

A symmetrical input or output circuit that has equal impedance from both input terminals
to a common ground reference point. The industry standard for professional and sound
recording installations, balanced connections have 6 dB more gain than single-ended
connections and allow the use of long interconnect cables. Balanced connections are
completely immune to induced noise from the system or the environment.

Single-ended

A two-wire input or output circuit. Use care when using single-ended connections as the
ground connection is made last and broken first. Turn the system off prior to making or
breaking single-ended connections. Single-ended connections are not recommended for
connections requiring long cable runs.

Krell KAV–2250 and KAV–3250 23

Questions and Answers

Q.

Should I turn the amplifier off when not playing music?

A.

No. Leave the amplifier in stand-by when not playing music. The stand-by mode
avoids cold starts as well as minimizes heat output and power consumption. Krell
recommends turning the amplifier off if you plan to be away for a period of time, for
example, on vacation. See

Amplifier Operation,

on page 13.

Q.

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 that all input and output connections and cables are of sound
construction. See

Troubleshooting System Noise

,

on page 14. 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.

Q.

When I connect the amplifier to my system using the single-ended inputs, a loud

buzz comes from my loudspeakers. What is it?

A.

Check that the shorting pins for the amplifier are inserted into the XLR inputs (the unit
is shipped with the pins in place). When using the single-ended inputs, the shorting pins
must be inserted between pins 1 and 3 to keep external noise from corrupting the
signal. For more information, see

Connecting the Amplifier to Your System

,

on page

11.

Q.

Can I bridge all the channels on my KAV–3250 amplifier?

A.

No. You can bridge two of the amplifier’s channels: 1 and 2. Channel 3 cannot be
bridged.

Q.

Will I be able to use the amplifier without reconfiguring the channels for MAT or

bridged operation?

A.

Yes. The amplifier is shipped from the factory ready to play music. The default
settings, see

Figure 5,

on page 16, allow you to connect each amplifier channel output

to a separate loudspeaker. MAT and bridging reconfigurations are optional.

Krell KAV–2250 and KAV–3250 3

Definition of Terms,

continued

OPERATION

Off

When the back panel power switch is in the down (off) position and the red stand-by
LED turns off, the component is off.

Stand-by Mode

When the AC power cord is plugged into the wall and the back panel power switch is in
the up (on) position, the red stand-by LED illuminates, indicating that the component is
in stand-by mode. This low power consumption status keeps the audio and regulator
circuits at idle. Krell recommends leaving the component in the stand-by mode when it
is not playing music.

Operational Mode

From the stand-by mode, when the power button on the front panel is pressed and the
blue power indicator illuminates, the component is in the operational mode and ready to
play music.

TECHNOLOGY

Krell Current Mode

A proprietary Krell circuit topology in which the audio gain stages of a component
operate in the current rather than voltage domain. This unique technology provides the
component with exceptional speed and a wide bandwidth.

4

Krell KAV–2250 and KAV–3250

Unpacking

1. Open the shipping box and remove the top layer of foam. You see these items:

1 amplifier unit (packed in foam end-caps)
1 IEC connector (AC power) cord

1 12 VDC output (12 V trigger) cable
1 T-15 Torx wrench
KAV–2250 fuses:
2 AGC-12 (12-amp)
or
KAV–3250 fuses:
3 AGC-12 (12-amp)
1 packet containing the owner’s reference manual
and the warranty registration card.

2. Locate the cutouts in the foam end caps.

3. Slip hands under cutouts and lift the amplifier straight out of the box.

4. 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 transit damage. See

Return Authorization Procedure,

on page 25, for more information.
The KAV–2250 weighs 64 lbs. and the KAV–3250 weighs 68 lbs. It may be more

convenient for two people to lift the amplifier out of the shipping box.

Krell KAV–2250 and KAV–3250 21

Reconfiguration Options,

continued

Connecting the Amplifier Reconfigured for MAT

1. Connect the cable from your source device to the balanced or single-ended input

you have selected to receive the signal. (For example, if you use the switch settings
shown in Figure 6 your source device is connected to input 1.)

2. Connect each amplifier channel output to a separate loudspeaker.

RECONFIGURING THE AMPLIFIER FOR BRIDGED OPERATION

Reconfiguring the KAV–2250 or the KAV–3250 to Bridge Channels 1 and 2

See Figures 8 and 9 on page 20

To send the signal from a source device connected to input 1,
with channels 1 and 2 bridged:

1. For input switch bank 1, push switch 1 up (on).

2. For input switch bank 2, push switch 1 up (on).

3. Push the bridge switch up (on) between input switch banks 1 and 2.

Notes

Amplifier channels 1 and 2 may be bridged. Channel 3 on the KAV–3250

cannot be

bridged.
The unbridged channel on the KAV–3250

may be connected to a separate loudspeaker

for normal operation.

Connecting the Amplifier Reconfigured for Bridged Operation

1. Connect the cable from the input device to the balanced or single-ended input you

have selected to receive the signal.

2. Connect the positive loudspeaker lead to the red binding post on the corresponding

amplifier channel marked “

BRIDGE

+.” Connect the negative loudspeaker lead to the

red binding post on the amplifier channel marked “

BRIDGE

-.”

IMPORTANT

Tighten binding posts by hand only.

Krell KAV–2250 and KAV–3250 5

Placement

Before you integrate your new amplifier into your system, please review the following
guidelines to choose the location for the component. This will facilitate a clean, trouble­free installation.

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

The amplifier does not require any type of special rack or cabinet for installation. For the
dimensions of your amplifier see

Specifications

,

on pages 26 and 27.

Place the amplifier as close to the loudspeakers as possible and keep the loudspeaker
cable length to a minimum. Loudspeaker 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 loudspeaker cables reduce the maximum power that is
delivered to the loudspeakers.

AC POWER GUIDELINES

Krell recommends operating the amplifier from a dedicated 15-amp AC power line.
Please contact your authorized Krell dealer, distributor, or Krell before using any
devices designed to alter or stabilize the AC power for the KAV–2250 and KAV–3250.
`

Power Cord

The KAV–2250 and KAV–3250 should be operated only with the power cord supplied.

KAV–2250

132

6 Krell KAV–2250 and KAV–3250

Figure 1 The KAV–2250 Front Panel

Figure 2 The KAV–3250 Front Panel

KAV–3250

132

1 Power Button
2 Stand-by LED
3 Power Indicator

Krell KAV–2250 and KAV–3250 19

Reconfiguration Options,

continued

Reconfiguring the KAV–2250 for MAT: Send One Input Signal
to Both Output Channels via Input 2

Not illustrated

To send the signal from a source device connected to input 2:

1. Push switch 2 up (on) for both input switch banks.

2. Push switch 1 down (off) for both input switch banks.

Reconfiguring the KAV–3250 for MAT: Send One Input Signal
to All Three Output Channels via Input 1

See Figure 7 on page 17

To send the signal from a source device connected to input 1:

1. Push switch 1 up (on) for all input switch banks.

2. Push switches 2 and 3 down (off) for all input switch banks.

Reconfiguring the KAV–3250 for MAT: Send One Input Signal
to All Three Output Channels via Any Input

Not illustrated

You can send the signal from any of the inputs, depending on your preference,
for example:

To send the signal from a source device connected to input 2:

1. Push switch 2 up (on) for all input switch banks.

2. Push switches 1 and 3 down (off) for all input switch banks.

or

To send the signal from a source device connected to input 3:

1. Push switch 3 up (on) for all input switch banks.

2. Push switches 1 and 2 down (off) for all input switch banks.