Krell 400-MCX Owners Reference
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 203-799-9954
FAX 203-891-2028
E-MAIL krell@krellonline.com
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. 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 dripping 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 connecting speakers. Do not connect the negative speaker terminals together. Do not connect the negative speaker terminals to ground or attempt to bridge the left and right speaker binding posts of Full Power Balanced stereo amplifiers.
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 Balanced 700cx, 400cx, and 300cx Stereo Power
Amplifiers and three monaural amplifiers, the
Full Power Balanced 750Mcx, 450Mcx, and
350Mcx Monaural Power Amplifiers. Installation, connection, and operation of all amplifiers
in the Full Power Balanced series are identical;
however, a pair of Full Power Balanced Monaural amplifiers are required for stereo operation.
Full Power Balanced amplifiers can be configured 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 important information on placement, installation, and
operation of the Full Power Balanced amplifiers. 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 operation for Krell systems that include multiple preamplifiers, amplifiers, and associated components. When Krell Link in/out connections are
used, the remote capabilities of the linked components are controlled from one component,
called the control component. The linked components 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. Balanced connections are completely immune to
induced noise from the system or the environment.
Krell Current Audio Signal Transmission
(CAST)
A proprietary Krell circuit technology for connecting 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. Singleended 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 illuminate, 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 recommends 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 accurate 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 algorithm utilized in the Master Reference Amplifier.
Sustained Plateau Bias III maximizes an amplifier’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 Current 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 system.
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. Internally, each CAST source transfers, or amplifies,
current using Krell Current Mode circuitry. This
current signal is then output using CAST circuitry. 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 Current Mode takes circuitry signal transmission to
the next evolutionary level. In essence, Krell
Current Mode maintains the integrity of the signal within the component and CAST preserves
the transmitted signal between components.
Together, CAST and Krell Current Mode technologies 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 aesthetically 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 developed for every CAST cable made.
The Best Musical Performance
When you operate a CAST system, you will
hear significant improvements in every performance 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 musical 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 cardboard 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 transit 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 clearance above the component to provide adequate ventilation.
Although Sustained Plateau Bias III circuitry
reduces the high heat dissipation and heat output 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 amplifier in a closed cabinet, you may need to modify
shelf spacing or use small fans to increase ventilation. 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 Technology 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 impedance 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 dedicated 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, distributor, or Krell before using any devices
designed to alter or stabilize the AC power for
Full Power Balanced amplifiers.
Placement, continued
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