Krell 300-CX, 350-MCX, 400-CX, 450-MCX, 750-MCX Owners manual

Instructions for Use

Owner’s Reference

THE LEADER IN AUDIO ENGINEERING

Full Power Balanced

X Series Power Amplifiers

700cx, 400cx, 300cx Stereo

750Mcx, 450Mcx, 350Mcx Monaural

with Krell CAST II Technology

Full Power Balanced

X Series Power Amplifiers

700cx, 400cx, 300cx Stereo

750Mcx, 450Mcx,

350Mcx Monaural

with Krell CAST II Technology

v 02.0

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 Indus-

tries, Inc., its subsidiaries, and authorized agents. Sustained Plateau Bias III™ is a trademark of Krell Industries, Inc. and is a Krell technology based on

U.S. Patent No. 5,331,291. CAST™, CAST II™, Krell Current Mode™, Krell Link™, and Krell Playback System™ are trademarks of Krell Industries, Inc.

All other trademarks are registered to their respective companies.

©

2002 by Krell Industries, Inc. All rights reserved P/N 305976

This product complies with the EMC directive (89/336/EEC) and the low-voltage directive (73/23/EEC).

WARNINGS

The Full Power Balanced amplifier must be placed on a firm, level surface where it is not exposed to drip-

ping or splashing.

The ventilation grids on the top of the Full Power Balanced amplifier must be unobstructed at all times during

operation. Do not place flammable material on top of or beneath the component.

Before making connections to the Full Power Balanced amplifier, ensure that it is off and the 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.

The differential circuitry employed with Full Power Balanced amplifiers requires special attention when connect-

ing speakers. Do not connect the negative speaker terminals together. Do not connect the negative speaker ter-

minals to ground or attempt to bridge the left and right speaker binding posts of Full Power Balanced stereo ampli-

fiers.

Do not connect a Full Power Balanced amplifier to a speaker selector device that employs a common

ground scheme, as it may short-circuit the amplifier output.

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.

Page

INTRODUCTION 1

DEFINITION OF TERMS 1

REVOLUTIONARY KRELL CAST and CAST II TECHNOLOGY 3

UNPACKING 4

PLACEMENT 4

AC Power Guidelines 5

FRONT PANEL DESCRIPTION 8

700cx, 400cx, and 300cx Stereo Power Amplifiers 8

750Mcx, 450Mcx, and 350Mcx Monaural Power Amplifiers 8

BACK PANEL DESCRIPTION 11

700cx, 400cx, and 300cx Stereo Power Amplifiers 11

750Mcx, 450Mcx, and 350Mcx Monaural Power Amplifiers 12

CONNECTING THE FULL POWER BALANCED AMPLIFIER

TO YOUR SYSTEM 13

Input and Output Connections 13

Krell Link Connections 13

DC Protection Circuitry 14

Using a Tube Preamplifier 14

AMPLIFIER OPERATION 15

On/Off and Stand-by Operation 15

Krell Link Operation 15

REMOTE CONTROL OPERATION 16

How to Turn Off the Amplifier LEDs 16

How to Turn On the Amplifier LEDs 16

How to Switch between Krell CAST and XLR Inputs 16

Using a Dedicated Wall Outlet and Switch 16

AMPLIFIER TROUBLESHOOTING 17

How to Troubleshoot System Noise 17

How to Evaluate Amplifier Operation 17

QUESTIONS AND ANSWERS 19

WARRANTY 20

RETURN AUTHORIZATION PROCEDURE 21

SPECIFICATIONS 22

Krell Full Power Balanced X Series Power Amplifiers iii

Contents

Page

FIGURE 1 Full Power Balanced Stereo Amplifier Front Panel 6

FIGURE 2 Full Power Balanced Monaural Amplifier Front Panel 7

FIGURE 3 Full Power Balanced Stereo Amplifier Back Panel 9

FIGURE 4 Full Power Balanced Monaural Amplifier Back Panel 10

iv Krell Full Power Balanced X Series Power Amplifiers

Illustrations

The Full Power Balanced X Series consists of

three stereo amplifiers, the Full Power Bal-

anced 700cx, 400cx, and 300cx Stereo Power

Amplifiers and three monaural amplifiers, the

Full Power Balanced 750Mcx, 450Mcx, and

350Mcx Monaural Power Amplifiers. Installa-

tion, connection, and operation of all amplifiers

in the Full Power Balanced series are identical;

however, a pair of Full Power Balanced Monau-

ral amplifiers are required for stereo operation.

Full Power Balanced amplifiers can be config-

ured to accommodate any sophisticated music

or home theater system and can be operated

by an optional remote control or through the

remote control of other Krell components.

This owner’s reference manual contains impor-

tant information on placement, installation, and

operation of the Full Power Balanced ampli-

fiers. Please read this information carefully. A

thorough understanding of these details will

help ensure satisfactory operation and long life

for your Full Power Balanced amplifier and

related system components.

Following are the definitions of key terms used

in your owner’s reference manual.

CONFIGURATIONS

Krell Link

A method of synchronizing remote control oper-

ation for Krell systems that include multiple pre-

amplifiers, amplifiers, and associated compo-

nents. When Krell Link in/out connections are

used, the remote capabilities of the linked com-

ponents are controlled from one component,

called the control component. The linked com-

ponents respond to stand-by and operational

mode commands from the control component

via MIDI cables.

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. Bal-

anced connections are completely immune to

induced noise from the system or the environ-

ment.

Krell Current Audio Signal Transmission

(CAST)

A proprietary Krell circuit technology for connect-

ing analog components, in which the audio

waveform is transmitted between components in

the current rather than voltage domain. The

speed and bandwidth provided by Krell CAST

and the CAST circuitry update, Krell CAST II,

yield accurate, realistic music reproduction. Krell

components connected via CAST and CAST II

perform as if they are all part of a single circuit.

Krell Full Power Balanced X Series Power Amplifiers 1

Definition of TermsIntroduction

2 Krell Full Powered Balanced X Series Power Amplifiers

Definition of Terms, continued

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.

OPERATION

Off

When the power switch on the back panel is

placed in the down position and the blue power

LEDs turn off, the component is off.

Operational Mode

When the power button on the front panel is

pressed and the three blue power LEDs illumi-

nate, the component is in the operational mode

and ready to play music.

Stand-by Mode

A low power consumption status that keeps the

audio and regulator circuits at idle. Krell recom-

mends leaving the component in the stand-by

mode when it is not playing 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.

Krell Sustained Plateau Bias III

A patented microprocessor control system that

maintains Class A bias operation regardless of

musical demand. Class Abias is the most accu-

rate method used to amplify musical signals.

The new Sustained Plateau Bias III software is

featured in the Full Power Balanced X Series

amplifiers and was developed from the algo-

rithm utilized in the Master Reference Amplifier.

Sustained Plateau Bias III maximizes an ampli-

fier’s efficiency both in power consumption and

heat generation.

Krell Full Power Balanced X Series Power Amplifiers 3

Current Audio Signal Transmission, termed

CAST, is a revolutionary method of connecting

analog audio components for unparalleled

sonic performance. CAST circuitry, and the

CAST circuitry update, Krell CAST II, combine

innovative engineering with existing Krell Cur-

rent Mode technology to create entire CAST

systems that reproduce music with incredible

range, tonality, and precision.

Voltage Signal Transmission

and the Traditional Audio System

Traditionally, signal is transmitted in the voltage

domain between two components. In an audio

system, each component is a discrete entity with

unique characteristics that act upon the musical

signal independently. Each component is

unaware of the other components in the system.

The cables that connect the components each

have their own electrical characteristics, which

affect the sonic presentation of the entire sys-

tem.

CAST: A New Approach

CAST circuitry recognizes signal transmitted in

the current domain instead of the voltage

domain between each component. CAST

transmission unifies the individual components

and their interconnects into an electrically

linked whole. The sonic presentation of the

entire system remains intact.

CAST Basics

Here’s how a CAST audio system works. Inter-

nally, each CAST source transfers, or amplifies,

current using Krell Current Mode circuitry. This

current signal is then output using CAST cir-

cuitry. When the signal is received by a CAST

input, Krell Current Mode circuitry again takes

over until the signal reaches the loudspeaker.

By maintaining the musical signal in the current

domain from beginning to end, an entire CAST

system behaves as if it is one component. With

CAST, anomalies of signal transmission between

components are eliminated. Cable impedances

and their effects on the transmitted signal are

non-existent.

How CAST and Krell Current Mode Interact

While CAST is a new method of transferring the

musical signal between components, its origin

stems from Krell Current Mode, the technology

developed to transfer the musical signal within

a component. CAST combined with Krell Cur-

rent Mode takes circuitry signal transmission to

the next evolutionary level. In essence, Krell

Current Mode maintains the integrity of the sig-

nal within the component and CAST preserves

the transmitted signal between components.

Together, CAST and Krell Current Mode tech-

nologies unify separate Krell components into a

single global circuit.

CAST Cable Construction

A CAST system uses cables manufactured by

Krell and other manufacturers specially

licensed by Krell. Thin and flexible CAST

cables are constructed with the same build

quality as other Krell products and are aesthet-

ically matched to the components that Krell

manufactures. An all-metal body and locking

connectors with gold contacts are part of the

standard no-compromise specification devel-

oped for every CAST cable made.

The Best Musical Performance

When you operate a CAST system, you will

hear significant improvements in every perfor-

mance area: speed, precision, dynamic range,

depth and width of the sound stage, transient

impact, tonal balance, harmonic distortion, and

more. The goal for CAST is the same company

goal used for all Krell products. Krell strives for

the delivery of the best performance of a musi-

cal event for you, using the full expression of

technology to date.

Revolutionary Krell CAST

and CAST II Technology

4 Krell Full Power Balanced X Series Power Amplifiers

Two people are needed to remove the Full

Power Balanced amplifier from its shipping box

safely and easily.

1. Open the shipping box and remove the top

layer of foam. You see these items:

1 Full Power Balanced Amplifier

1 Packet containing the owner’s

reference manual and the warranty

registration card

2. Orient the shipping box so that one person

stands at the front of the amplifier and one

person stands at the rear of the amplifier.

Both people need to grab a pair of the card-

board handle cutouts (one pair located at the

front of the amplifier and one pair located at

the rear of the amplifier) and simultaneously

lift the amplifier straight up, out of the carton.

3. Place the amplifier in a safe location and

remove the protective plastic wrapping.

Notes

If any of the items mentioned above 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 Full

Power Balanced amplifier in the future, repack

the unit in its original packaging to prevent tran-

sit damage. See Return Authorization Proce-

dure, on page 21 for more information.

Before you install the Full Power Balanced

amplifier into your system, please follow the

guidelines in this section to choose its proper

location. This will facilitate a clean, trouble-free

installation.

The Full Power Balanced amplifier requires at

least two inches (5 cm) of clearance on each

side and at least eight inches (20 cm) of clear-

ance above the component to provide ade-

quate ventilation.

Although Sustained Plateau Bias III circuitry

reduces the high heat dissipation and heat out-

put of traditional Class A circuitry, Full Power

Balanced amplifiers still can become hot under

normal operation.

When the front and rear of a cabinet are open

the air space between the chassis and shelf

must be unobstructed. If you place the amplifi-

er in a closed cabinet, you may need to modify

shelf spacing or use small fans to increase ven-

tilation. For the dimensions of your Full Power

Balanced amplifier, see Specifications, on

pages 22–23.

Place the amplifier as close to the speakers as

possible. Krell CAST technology permits you to

use interconnect cables of any length, see Rev-

olutionary Krell CAST and CAST II Technol-

ogy on page 3; however, try to keep the cable

length to a minimum.

All Full Power Balanced amplifiers drive the

lowest impedances with ease. When imped-

ance is added due to long speaker cable

lengths, amplifier power is wasted in the cable.

Long speaker cables reduce the maximum

power that is delivered in the speakers.

Unpacking Placement

Krell Full Power Balanced X Series Power Amplifiers 5

AC POWER GUIDELINES

The Full Power Balanced 300cx and 350Mcx

amplifiers need to be operated from a dedicat-

ed AC power line rated at a minimum of 15

amps. The Full Power Balanced 700cx,

750Mcx, 400cx, and 450Mcx amplifiers need to

be operated from a dedicated AC power line

rated at a minimum of 20 amps.

Please contact your authorized Krell dealer, dis-

tributor, or Krell before using any devices

designed to alter or stabilize the AC power for

Full Power Balanced amplifiers.

Placement, continued