Krell Industries 200c, 300c, 650Mc, 600c, 250Mc Instructions For Use Manual
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Full Power Balanced
Power Amplifiers
200c, 300c, 600c Stereo
250Mc, 350Mc, 650Mc Monaural
with Krell CAST Technology
Instructions for Use
Owner’s Reference
Full Power Balanced
Power Amplifiers
200c, 300c, 600c Stereo
250Mc, 350Mc, 650Mc Monaural
with Krell CAST Technology
v 00.0
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 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 ff 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 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.
This ;~roduct is manufactured in the United States of America. Krell~ is a registered trademark of Krell Industries. Inc.. and is restricted for use by Krell Industdes. Inc., its subsidiaries, and authorized agents. Sustained Plateau Bias II is a patent of Krell Industries, Inc. Krell CAST
TM
is a patent pending of Krell
Industries, Inc. Krell Current Mode
TM,
Krell Link
TM,
and Krell Playback System
TM
are trademarks of Krell Industries, Inc. All other trademarks are registered
to their respective companies.
©2000 by Krell Industries, Inc. All rights reserved P/N 303969
Contents
INTRODUCTION
DEFINITION OF TERMS
REVOLUTIONARY KRELL CAST TECHNOLOGY
UNPACKING
PLACEMENT
AC Power Guidelines
FRONT PANEL DESCRIPTION
200c, 300c, and 600c Stereo Power Amplifiers
250Mc, 350Mc, and 650Mc Monaural Power Amplifiers
BACK PANEL DESCRIPTION
200c, 300c, and 600c Stereo Power Amplifiers
250Mc, 350Mc, and 650Mc Monaural Power Amplifiers
CONNECTING THE FULL POWER BALANCED AMPLIFIER
TO YOUR SYSTEM
Input and Output Connections
Krell Link Connections
DC Protection Circuitry
Using a Tube Preamplifier
AMPLIFIER OPERATION
On/Off and Stand-by Operation
Krell Link Operation
REMOTE CONTROL OPERATION
How to Tum Off the Amplifier LEDs
How to Tum on the Amplifier LEDs
How to Switch between Krell CAST and XLR Inputs
Using a Dedicated Wall Outlet and Switch
AMPLIFIER TROUBLESHOOTING
How to Troubleshoot System Noise
How to Evaluate Amplifier Operation
QUESTIONS AND ANSWERS
WARRANTY
RETURN AUTHORIZATION PROCEDURE
SPECIFICATIONS
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Krell Full Power Balanced Power Amplifiers iii
Illustrations
FIGURE 1 Full Power Balanced Stereo Amplifier Front Panel
FIGURE 2 Full Power Balanced Monaural Amplifier Front Panel
FIGURE 3 Full Power Balanced Stereo Amplifier Back Panel
FIGURE 4 Full Power Balanced Monaural Amplifier Back Panel
Page
6
7
9
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iv
Krell Full Power Balanced Power Amplifiers
Introduction Definition of Terms
The Full Power Balanced series of amplifiers
consists of three stereo amplifiers, the Full
Power Balanced 200c, 300c, and 600c, and
three monaural amplifiers, the Full Power Bal-
anced 250Mc, 350Mc, and 650Mc. 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 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 com ponents.
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 pre-
amplifiers, amplifiers, and associated components. 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. 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
yields accurate, realistic music reproduction.
Krell components connected via CAST perform
as if they are all part of a single circuit.
Krell Full Power Balanced Power Amplifiers
1
Definition of Terms, co,,tinuo,
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 II
A proprietary Krell digital circuit that continually
monitors the input signal and output impedance
of a Krell amplifier and adjusts the bias accordingly to ensure Class A operation. Sustained
Plateau Bias II provides the enormous sonic
benefits of continuous Class A operation while
minimizing the heat generation and power consumption normally associated with Class A
designs.
2 Krell Full Powered Balanced Power Amplifiers
Revolutionary Krell CAST
Technology
Current Audio Signal Transmission, termed
CAST, is a revolutionary method of connecting
analog audio components for unparalleled
sonic performance. Innovative engineering
combines the new Krell CAST circuitry with
existing Krell Current Mode technology to cre-
ate 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 trans-
mission 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 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 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 aesthetically
matched to the components that Krell manufactures. An all-metal body and locking connectors
with gold contacts are part of the standard nocompromise specification developed for evenj
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.
Krell Full Power Balanced Power Amplifiers 3
Unpacking Placement
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
ff 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 unff in its original packaging to prevent transit damage. See Return Authorization Procedure, 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 ade-
quate ventilation.
Although Sustained Plateau Bias II 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 an~l 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 Flev-
olutionary CAST Technology on page 3;
however, try to keep the cable length to a mini-
mum.
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.
4 Krell Full Power Balanced Power Amplifiers
Placement, continued
AC POWER GUIDELINES
The Full Power Balanced 200c and 250Mc
amplifiers need to be operated from a dedicat-
ed AC power line rated at a minimum of 15
amps. The Full Power Balanced 300c, 350Mc,
600c, and 650Mc amplifiers need to be operat-
ed 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.
Krell Full Power Balanced Power Amplifiers 5
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