Krell 350-MCX, FPBX Owners manual
Full Power Balanced
X Series Power Amplifiers
700cx, 400cx, 300cx Stereo
750Mcx, 450Mcx, 350Mcx Monaural
with Krell CAST II Technology
THE LEADER IN AUDIO ENGINEERING
Instructions for Use
Owner’s Reference
Krell Industries, Inc.
45 Connair Road
Orange, CT 06477-3650 USA
TEL 203-799-9954
FAX 203-891-2028
E-MAIL krell@krellonline.com
WEB SITE http://www.krellonline.com
This product complies with the EMC directive (89/336/EEC) and the low-voltage
directive (73/23/EEC).
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 ques-
tions not addressed in this reference m anual.
© 2003 by Krell Industries, Inc. All rights reserved P/N 305976
Full Power Balanced
X Series Power Amplifiers
700cx, 400cx, 300cx Stereo
750Mcx, 450Mcx, 350Mcx Monaural
with Krell CAST II Technology
Instructions for Use
v 03.0
CONTACT
INFORMATION
WARNINGS
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.
Contents
Krell Full Power Balanced X Series Power Amplifiers iii
Page
INTRODUCTION 1
DEFINITION OF TERMS 2
REVOLUTIONARY KRELL CAST and CAST II TECHNOLOGY 4
UNPACKING 6
PLACEMENT 7
AC Power Guidelines 7
FRONT P ANELDESCRIPTION 8
700cx, 400cx, and 300cx Stereo Power Amplifiers 8
750Mcx, 450Mcx, and 350Mcx Monaural Power Amplifiers 8
BACK PANEL DESCRIPTION 10
700cx, 400cx, and 300cx Stereo Power Amplifiers 10
750Mcx, 450Mcx, and 350Mcx Monaural Power Amplifiers 10
CONNECTING THE FULL POWER BALANCED AMPLIFIER
TO YOUR SYSTEM 13
Input and Output Connections 13
Krell Trigger Connections 14
DC Protection Circuitry 14
Using a Tube Preamplifier 15
AMPLIFIER OPERATION 16
On/Off and Stand-by Operation 16
Krell Trigger Operation 17
REMOTE CONTROL OPERATION 18
How to Turn Off the Amplifier LEDs 18
How to Turn On the Amplifier LEDs 18
How to Switch between Krell CAST and XLR Inputs 18
Using a Dedicated Wall Outlet and Switch 18
AMPLIFIER TROUBLESHOOTING 19
How to Troubleshoot System Noise 19
How to Evaluate Amplifier Operation 19
QUESTIONS AND ANSWERS 21
WARRANTY 23
RETURN AUTHORIZA TION PROCEDURE 24
SPECIFICA TIONS 25
Illustrations
Page
FIGURE 1 The Full Power Balanced Stereo Amplifier 8
Front Panel
FIGURE 2 The Full Power Balanced Monaural Amplifier 8
Front Panel
FIGURE 3 The Full Power Balanced Stereo Amplifier 10
Back Panel
FIGURE 4 The Full Power Balanced Monaural Amplifier 10
Back Panel
iv Krell Full Power Balanced X Series Power Amplifiers
Krell Full Power Balanced X Series Power Amplifiers 1
Introduction
Thank you for your purchase of a Full Power Balanced X Series
Power Amplifier.
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. Athorough understanding of these details will help ensure satisfactory operation and
long life for your Full Power Balanced amplifier and related system
components.
2 Krell Full Power Balanced X Series Power Amplifiers
Definition of Terms
Following are the definitions of key terms used in your owner’s reference manual.
Krell Trigger
Amethod of synchronizing remote control operation for Krell systems that include multiple preamplifiers, amplifiers, and associated
components. When Krell Trigger 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.
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)
Aproprietary 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.
Single-ended
A two-wire input or output circuit. Use care when using singleended connections as the ground connection is made last and broken first. Turn the system off prior to making or breaking singleended connections. Single-ended connections are not recommended for connections requiring long cable runs.
CONFIGURATIONS
INPUT AND OUTPUT
CONNECTIONS
Krell Full Power Balanced X Series Power Amplifiers 3
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.
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.
Definition of Terms,
continued
OPERATION
TECHNOLOGY
4 Krell Full Power Balanced X Series Power Amplifiers
Revolutionary Krell CAST
and CAST II Technology
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 II 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 compo-
Krell Full Power Balanced X Series Power Amplifiers 5
nent 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 CAST Technology,
continued
6 Krell Full Power Balanced X Series Power Amplifiers
Unpacking
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 Quick Setup Guide 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 back 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 back 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.
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 Procedure on
page 24, for more information.
Notes
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