Krell Industries Stereo Amplifier 400 User Manual

EVOLUTION  
EVOLUTION AMPLIFIERS  
302 AND 402 STEREO  
403 THREE-CHANNEL  
400, 600, AND 900 MONAURAL  
OWNER’S REFERENCE  
 
Contents  
List of Illustrations, page 4  
A Letter from Dan D’Agostino, page 5  
SECTION ONE: Evolution Amplifier Features and Technology, page 6  
Features, Revolutionary Krell CAST Technology,  
Definition of Terms  
SECTION TWO: Unpacking and Placement, page 11  
Opening the Evolution Amplifier Shipping Carton  
SECTION THREE: Anatomy of the Evolution Amplifier, page 13  
Front Panel Description, and Back Panel Description  
SECTION FOUR: Connecting an Evolution Amplifier to Your System, page 22  
CAST Connections, Balanced Connections, Single-ended Connections,  
Evolution DC Protection Circuitry/Using Tube Preamplifiers, Connection Steps  
SECTION FIVE: Evolution Amplifier Operation, page 24  
On/Off and Stand-by Operation  
SECTION SIX: Troubleshooting System Noise, page 25  
How to Evaluate Amplifier Operation, Error Codes  
SECTION SEVEN: Questions and Answers, page 27  
WARRANTY, page 28  
RETURN AUTHORIZATION PROCEDURE, page 30  
SPECIFICATIONS, page 31  
3
 
List of Illustrations  
Figure 1, page 13  
Evolution Amplifier Front Panel  
Figure 2, page 15  
Evolution 302 Stereo Back Panel  
Figure 3, page 16  
Evolution 402 Stereo Amplifier Back Panel  
Figure 4, page 17  
Evolution 403 Three-channel Amplifier Back Panel  
Figure 5, page 18  
Evolution 400 Monaural Amplifier Back Panel  
Figure 5, page 19  
Evolution Monaural Amplifier Back Panel  
4
 
A Letter from Dan D’Agostino  
Dear Audio Enthusiast,  
Thank you for your purchase of a Krell Evolution Series amplifier.  
Evolution Series amplifiers continue my quest for amplifiers that deliver absolute  
truth in music reproduction. Active Cascode Topology is a unique circuit technique  
that minimizes distortion by applying from 2 to 3 times more active devices to  
each gain stage. The attributes of this topology is shared throughout the Evolution  
Series amplifiers.  
Krell amplifiers are best known for their ability to drive any loudspeaker to sound  
its best, without regard to impedance or efficiency. I believe that linearity, an  
amplifier’s ability to output an exact duplicate of the input signal, is the ultimate  
measure of that amplifier’s work. At Krell, I drive amplifier designs toward the com-  
mon goal of linearity, through the rigorous application of Krell design principles  
that focus our efforts on four major performance factors: distortion, bandwidth,  
output impedance, and current capability. The Evolution Series amplifiers are a  
synthesis of these factors.  
The Evolution Series amplifiers use Evolution CAST technology, for superior per-  
formance and very low noise.  
I hope that you enjoy your new Evolution Series amplifier.  
Sincerely,  
Daniel D’Agostino  
Chief Executive Officer  
5
 
SECTION  
ONE  
Evolution Amplifier Features and Technology  
This section describes the innovative features and technology of the Evolution  
Series amplifiers, and defines CAST and other key terms used in this reference.  
There are six amplifier models in the Evolution Series: the 302 Stereo Power  
Amplifier, the 402 Stereo Power Amplifier, the 403 Three-channel Power Amplifier,  
the 400 Monaural Power Amplifier, the 600 Monaural Power Amplifier, and the 900  
Monaural Power Amplifier. The compact chassis of the 400 Monaural Power  
Amplifier contains all of the high power, wide bandwidth, and low noise character-  
istics designed into all Evolution Series amplifiers.  
Features  
Evolution Series amplifiers are designed with a signal path that incorporates Krell  
Current Mode and CAST circuitry.  
All amplifiers feature massive power supplies. The power supply makes use of  
extensive electrical and magnetic shielding to keep radiated interference out of  
critical amplifier circuits.  
The Evolution 302 design utilizes a 3000 VA power supply. The Evolution 402 and  
Evolution 600 are equipped with a 5000 VA power supply, and the Evolution 403  
and Evolution 900 house 6000 VA power supplies.  
Internal high-current line conditioning circuitry filters RF noise on the AC mains, as  
well as compensating for asymmetrical power waveforms and DC on the mains.  
Advanced microprocessor control monitors critical operational parameters. Output  
current, DC offset, rail voltages, and operating temperature are all continuously  
monitored.  
6
 
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 create entire CAST systems that reproduce music  
with incredible range, tonality, and precision.  
The 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 characteris-  
tics that act upon the musical signal independently. Each component is unaware  
of the other components in the system. The cables that connect the components  
also have their own electrical characteristics, which affect the sonic presentation  
of the entire system. CAST transmission unifies individual components and inter-  
connects into an electrically-linked whole. The original signal remains unaltered  
from source to speaker.  
CAST Basics  
Here is 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, circuit board  
properties and signal transmission aberrations between components are eliminat-  
ed. 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 compo-  
nents, its origin stems from Krell Current Mode, the technology developed to  
transfer the musical signal within a component. CAST combined with Krell Current  
Mode circuitry takes signal transmission to the next evolutionary level. In essence,  
continued  
7
 
(SECTION ONE: Evolution Amplifier Features and Technology continued)  
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. Krell Current Mode technology enjoys bandwidth increases up to an  
order of magnitude greater than their voltage based counterparts. This dramatic  
increase in circuit bandwidth delivers near perfection in the audible band that typi-  
cally suffers from phase distortions in voltage circuits.  
CAST Cable Construction  
A CAST system uses cables manufactured by Krell and other manufacturers spe-  
cially licensed by Krell. Thin and flexible CAST cables are constructed with the  
same build quality as other Krell components 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 devel-  
oped for every CAST cable made.  
Evolution CAST  
By employing revolutionary current mirror circuitry, the Evolution amplifier compo-  
nents raises CAST technology to another level. This advanced use of the technol-  
ogy increases the linearity, transient speed, and bandwidth of the Evolution com-  
ponents while reducing the distortion by an order of magnitude.  
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 expres-  
sion of technology to date.  
8
 
Definition of Terms  
The following are definitions of key terms used in this owner’s reference:  
Inputs and Outputs  
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 profes-  
sional 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.  
CAST and Evolution CAST  
Krell Current Audio Signal Transmission, or CAST, is a proprietary Krell circuit tech-  
nology for connecting analog components, transmitting the audio waveform  
between components in the current domain rather than in the voltage domain. The  
speed and bandwidth provided by Krell CAST and its circuitry update, Evolution  
CAST, yield accurate, realistic music reproduction, enabling connected compo-  
nents to perform as if they are all part of a single circuit. CAST and Evolution CAST  
are balanced connections, and reject induced noise.  
Single-ended  
A two-wire input or output circuit. Single-ended connections are not recommend-  
ed for connections requiring long cable runs. Use care when using single-ended  
connections, because the ground connection is made last and broken first. Turn  
the system off/on prior to making or breaking single-ended connections.  
Operation  
Off  
When the power status indicator is not illuminated, the amplifier is off.  
Stand-by  
A low-power-consumption status that keeps the audio and power supply circuits  
at idle. The power status indicator is illuminated in red, when the amplifier is in  
stand-by mode. Krell recommends leaving the amplifier in stand-by mode when it  
is not playing music.  
Operation  
When the power button is pressed, and the power status indicator is illuminated in  
blue, the amplifier is in operational mode and ready to play music.  
continued  
9
 
(SECTION ONE: Definition of Terms continued)  
Technology  
Active Cascode Topology  
A unique circuit technique that minimizes distortion by applying from 2 to 3 times  
more active devices to each gain stage thereby reducing the load on individual  
devices and improving circuit-wide linearity.  
Krell Current Mode  
A proprietary Krell circuit topology in which the audio gain stages of a component  
operate in the current domain rather than the voltage domain. This unique technol-  
ogy provides the component with exceptional speed, and a wide bandwidth.  
10  
 
SECTION  
TWO  
Unpacking and Placement  
This section describes the procedures for safely unpacking and placing your  
Evolution amplifier. The amplifier and accessories are shipped in 1 carton. The  
dimensions of the amplifier are shown in the specifications section starting on  
page 31.  
Two people are needed to remove the Evolution amplifier from its shipping box  
safely and easily.  
Opening the Evolution Amplifier Shipping Carton  
1. Open the shipping carton and remove the top layer of foam. The carton con-  
tains these items:  
1 Evolution amplifier chassis  
1 20 amp AC power cord  
1 12 VDC (12 V trigger) cable  
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. Bend and lift with your knees,  
not your back.  
3. Place the amplifier in a safe location, and remove the protective plastic wrap-  
ping.  
Note  
Save all packing materials. If you need to ship the Evolution amplifier in future, repack  
the unit in its original packaging to prevent shipping damage.  
continued  
11  
 
(SECTION TWO: Unpacking and Placement continued)  
Placement  
Before you install an Evolution amplifier into your system, please follow the guide-  
lines in this section to select a location for your component. This will facilitate a  
clean, trouble-free installation.  
Place the amplifier on a firm, level surface, away from excessive heat, humidity, or  
moisture. Each Evolution 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.  
If you place the amplifier in a closed cabinet, you may need to modify shelf spac-  
ing or use small fans to increase ventilation. When the front and back of a cabinet  
are open, the air space between the chassis and shelf must be unobstructed.  
Place the amplifier(s) as close to the loudspeakers as possible. While Evolution  
CAST technology permits long interconnect cable lengths, keep loudspeaker  
cable lengths to a minimum.  
AC Power Guidelines  
The Evolution amplifier requires a dedicated AC circuit rated at a minimum of 20  
amps. Do not use extension cords, multiple AC adapters, or AC power strips.  
Note  
Do not operate the Evolution amplifiers with any device designed to alter or condition  
AC power.  
12  
 
SECTION  
THREE  
Anatomy of an Evolution Amplifier  
This section describes Evolution amplifier functions.  
Figure 1 Evolution Amplifier Front Panel (Evolution 402 shown)  
1 Power Button  
Power  
2 Power Status Indicator  
continued  
13  
 
(SECTION THREE: Anatomy of an Evolution Amplifier continued)  
Front Panel Description  
See Figure 1 on the previous page  
Evolution amplifier front panel functions are described below:  
Power  
1 Power Button  
Press this button to place the Evolution amplifier in operational mode.  
2 Power Status Indicator  
The power status indicator is illuminated in red when the amplifier is in stand-  
by mode. The indicator illuminates in blue when the amplifier is in operational  
mode. If there is no illumination, please check the following items:  
—The power cord is connected to the amplifier  
—The power cord is plugged into a live AC power supply  
—The back panel power breaker switch (10) is set to the on position  
—The back panel backlight switch (8) is set to the on/ext position  
—There is no 12 VDC controller connected to the EXT IN connector  
14  
 
Figure 2 Evolution 302 Stereo Amplifier Back Panel  
Outputs  
Inputs  
3 Loudspeaker Binding Posts  
4 CAST Inputs  
5 Single-ended Inputs  
6 Balanced Inputs  
7 12 VDC Out/In (12 V Trigger)  
8 Backlight Control  
9 IEC Power Cord Receptacle  
10 Power Breaker Switch  
Remote  
Power  
continued  
15  
 
Figure 3 Evolution 402 Stereo Amplifier Back Panel  
Outputs  
Inputs  
3 Loudspeaker Binding Posts  
4 CAST Inputs  
5 Single-ended Inputs  
6 Balanced Inputs  
7 12 VDC Out/In (12 V Trigger)  
8 Backlight Control  
9 IEC Power Cord Receptacle  
10 Power Breaker Switch  
Remote  
Power  
16  
 
(SECTION THREE: Anatomy of an Evolution Amplifier continued)  
Figure 4 Evolution 403 Multi-channel Amplifier Back Panel  
Outputs  
Inputs  
3 Loudspeaker Binding Posts  
4 CAST Inputs  
5 Single-ended Inputs  
6 Balanced Inputs  
7 12 VDC Out/In (12 V Trigger)  
8 Backlight Control  
9 IEC Power Cord Receptacle  
10 Power Breaker Switch  
Remote  
Power  
continued  
17  
 
Figure 5 Evolution 400 Monaural Amplifier Back Panel  
Outputs  
3 Loudspeaker Binding Posts  
4 CAST Input  
5 Single-ended Input  
6 Balanced Input  
7 12 VDC Out/In (12 V Trigger)  
8 Backlight Control  
9 IEC Power Cord Receptacle  
10 Power Breaker Switch  
Remote  
Power  
18  
 
Figure 6 Evolution Monaural Amplifier Back Panel (Evolution 600 shown)  
Outputs  
Inputs  
3 Loudspeaker Binding Posts  
4 CAST Input  
5 Single-ended Input  
6 Balanced Input  
7 12 VDC Out/In (12 V Trigger)  
8 Backlight Control  
9 IEC Power Cord Receptacle  
10 Power Breaker Switch  
Remote  
Power  
19  
 
(SECTION THREE: Anatomy of an Evolution Amplifier continued)  
Back Panel Description  
See Figures 2, 3, 4, 5, and 6 on the previous pages  
The amplifier back panel provides access to the input and output connections,  
12 V trigger inputs and outputs, and the AC power connection and switch. Back  
panel features and their descriptions follow:  
Outputs  
3 Loudspeaker Binding Posts (one pair per channel)  
Each channel has one positive and one negative binding post. They accept  
spade lugs only.  
Inputs  
4 CAST Inputs (one per channel)  
These are CAST inputs with 4-pin bayonet connectors, for use with Krell  
CAST-equipped preamplifiers and components.  
5 Single-ended Inputs (one per channel)  
These are single-ended analog inputs with RCA connectors.  
6 Balanced Inputs (one per channel)  
These are balanced analog inputs with XLR connectors.  
continued  
20  
 
Remote Connections  
7 12 VDC In/Out (12 V Trigger)  
The 12 V trigger allows you to turn the Evolution amplifier on or to stand-by  
from other components.  
Out. The output sends 12 VDC (12 V trigger) power on/off signals to other Krell  
components and other devices that incorporate a 12 V trigger, allowing whole  
systems or parts of systems to be easily controlled remotely. Mono 3.5 mm  
connectors are used in the following configuration: Tip = +12 V, Sleeve = GND.  
Notes  
When an Evolution amplifier is in the operational mode, the 12 V trigger provides 12 Volts  
of DC output. When the amplifier is in the stand-by mode or off, the DC output is  
0 Volts. A maximum of 30 mA is available from the 12 V trigger output.  
Consult the owner's reference of the components used in a custom installation to take  
full advantage of the remote capabilities of an Evolution amplifier.  
8 Backlight Control  
Ext In. Connect a 12 V trigger to the Ext In input connector to turn off the  
power status indicator (2) using a remote control. The switch must be set to  
On/Ext, in order for this to function (see below).  
On/Ext. This activates the power status indicator. (This is the factory default  
position.)  
Off. This turns off the power status indicator, during normal operation. The  
power status indicator remains illuminated for ten seconds after the power but-  
ton is pressed.  
Power  
9 IEC Power Cord Receptacle  
The power receptacle is for use with the provided 20 amp AC power cord. Use  
only the power cord supplied with your Evolution amplifier.  
10 Power Breaker Switch  
Place this switch in the up position to put the amplifier in stand-by mode.  
Place the switch in the down position to turn off the amplifier.  
21  
 
SECTION  
FOUR  
Connecting an Evolution Amplifier  
to Your System  
This section describes Evolution amplifier connections. Each Evolution amplifier  
channel has a CAST 4-pin connector, a balanced input via an XLR connector, a  
single-ended RCA connector, and a pair of loudspeaker binding posts. The rear  
panel also has 12 VDC trigger input and outputs, and a backlight remote trigger  
input. All inputs and outputs are located on the Evolution amplifier back panel.  
Maintain the correct left/right orientation, when hooking up your system.  
CAST Connections  
Krell recommends using its proprietary Krell CAST system for unparalleled sonic  
performance for connections between the Evolution amplifier and other CAST-  
equipped components. Krell CAST uses flexible interconnecting cables that can  
be drawn through tight spaces and concealed.  
Balanced Connections  
The Evolution amplifier also offers balanced operation. The circuitry and connec-  
tions associated with balanced operation not only can minimize sonic loss but  
also are immune to induced noise, especially for installations using long cables.  
XLR Pin Configuration  
Pin 1  
Pin 2  
Pin 3  
Ground  
O
Non-inverting (0 ) (hot)  
O
Inverting (180 ) (cold)  
Single-ended Connections  
Each Evolution amplifier channel has one single-ended input. If connecting a vacuum  
tube preamplifier, use the single-ended inputs only (see below). Connect the u-shap-  
ed jumpers between pins 1 and 3 of the XLR connectors when using single-ended  
inputs.  
continued  
22  
 
Evolution DC Protection Circuitry/Using Tube Preamplifiers  
The high DC output of tube preamplifiers may exceed the active DC protection  
circuitry of the Evolution amplifiers. Excessive DC level in a signal can damage  
amplifiers, loudspeakers, or both. The single-ended inputs of the Evolution ampli-  
fiers are capacitor-coupled and DC does not pass through. Therefore, if connect-  
ing a tube preamplifier, use the single-ended inputs only. For more information  
about DC protection circuitry features, see Error Codes on page 26.  
Connection Steps  
Position the amplifier where you intend to use it in your system.  
The following steps describe how to connect an Evolution amplifier to your sys-  
tem:  
1. Turn off all power sources and components before connecting inputs and out-  
puts.  
2. Neatly arrange and organize wiring to and from the Evolution amplifier and all  
components. Separate AC wires from audio cables to prevent hum or other  
unwanted noise from being introduced into the system.  
3. Connect the outputs of your preamplifier to the appropriate CAST (4), balanced  
(6), or single-ended inputs (5) on the Evolution amplifier.  
Note  
Connect the u-shaped jumpers between pins 1 and 3 of the XLR connectors when  
using single-ended inputs.  
4. Connect the loudspeaker cables to the loudspeaker binding posts (7) on the  
Evolution amplifier. The binding posts accept spade lugs only. Take care to  
observe the correct polarity when making connections: The positive (+) output  
connects to the positive input of the loudspeaker. The negative (-) output con-  
nects to the negative input of the loudspeaker.  
5. Connect the supplied AC power cord to the AC power cord receptacle (9).  
6. Plug the AC power cord into AC power.  
Note  
Use only the power cord provided with the Evolution amplifier to make the connection  
to AC power. Operation with a power cord other than the one supplied by Krell could  
induce noise, limit current, or otherwise impair the ability of the amplifier to perform  
optimally.  
23  
 
SECTION  
FIVE  
Evolution Amplifier Operation  
The Evolution amplifiers are easy to operate.  
IMPORTANT  
When powering up any system, turn the amplifier on last. When powering down, turn  
it off first. This will prevent any turn-on and turn-off thumps in your loudspeakers.  
Always mute or fully attenuate the preamplifier level when switching sources. Do not  
change input connections to the amplifier when the amplifier is on.  
Krell amplifiers have large reserves of clean power that can safely drive loudspeakers  
to higher sound pressure levels than other amplifiers. Use care when setting high play-  
back levels, and lower the volume level at the first sign of loudspeaker distress.  
On/Off and Stand-by Operation  
1. Move the back panel power breaker switch (10) to the up position to place the  
amplifier in stand-by mode. The power status indicator (2) illuminates in red.  
2. Press the silver power button (1) on the amplifier front panel. The power status  
indicator (2) illuminates in blue.  
The initial power-up phase lasts approximately 30 seconds from the moment  
the back panel power breaker switch is placed in the up position. If the power  
button is pressed during this period, the power status indicator flashes blue for  
the remainder of the initial power-up phase. When the initial power-up phase is  
complete, the power indicator illuminates in blue and is no longer flashing. The  
amplifier is in the operational mode.  
3. With the preamplifier muted or its volume completely lowered, select a source.  
4. Increase the volume control to the desired listening level.  
5. To return the amplifier to stand-by, press the power button on the front panel.  
The power status indicator turns red, and the amplifier is in the stand-by  
mode.  
It is now safe to place the rest of the system in stand-by.  
Powering Off  
Krell recommends leaving Evolution amplifiers in the stand-by mode between lis-  
tening sessions. Turn the amplifier off using the power breaker switch (10), and  
disconnect the amplifier from AC power when the system is not being used for an  
extended period of time.  
24  
 
SECTION  
SIX  
Troubleshooting System Noise  
AC grounding becomes critical when connecting high-performance audio compo-  
nents. When you mix and match high-performance audio components, each with  
its own ground potential, a low frequency hum may occur in one or both loud-  
speakers. This often occurs when introducing a new component into a system.  
If this happens when you place the Evolution amplifier into your system, follow  
these simple troubleshooting steps.  
Note  
During these steps, the back panel power breaker switch remains in the on position.  
1. Check that all input and output connections are of sound construction.  
2. With the amplifier in stand-by mode, remove the interconnect cables, then turn  
the amplifier on. If the hum disappears, turn the amplifier into stand-by mode  
again, and reinsert one of the interconnect cables. Turn the amplifier back on.  
Repeat this process for each cable.  
3. If the hum reappears with one or both interconnect cables reinserted, the cable  
needs to be checked.  
4. If the interconnect cables are sound, you may be experiencing a ground loop.  
Please contact your authorized Krell dealer, distributor, or Krell for suggestions  
on how to eliminate the ground loop.  
How to Evaluate Amplifier Operation  
The amplifiers are protected by a series of non-intrusive circuits that constantly  
evaluate the amplifier’s operation. This circuitry protects against damaging DC  
input or output, and short circuits. The protection circuitry in an Evolution amplifier  
is designed to prevent damage to the amplifiers or loudspeakers caused by other  
defective components, faulty wiring, system mishandling, or amplifier failure.  
25  
 
(SECTION SIX: Troubleshooting continued)  
Error Codes  
In the event of a problem, the power status indicator (2) will flash error code(s) in  
red. Errors are identified by a sequence of 3, 4, or 5 flashes. There is a pause  
between codes, and in the case where there is only one error code, the same  
code is repeated.  
Diagnostic Code  
Possible Condition  
Course of Action  
3 flashes  
Excessive current draw  
Check loudspeaker and  
cables for short circuits.  
If you are driving more  
than one loudspeaker  
per channel, check that  
the combined load does  
not drop below 2 Ohms.  
The power breaker  
switch must be shut off  
to reset the fault condi-  
tion.  
4 flashes  
5 flashes  
Excessive temperature  
Excessive DC at input  
Allow the amplifier to  
cool, and increase venti-  
lation. If the problem  
persists, please call the  
factory.  
Check the preamplifier  
output and source out-  
puts for excessive DC  
voltage.  
If you are using a vacuum  
tube preamplifier, use  
only the single-ended  
inputs, as they are  
capacitor coupled.  
26  
 
SECTION  
SEVEN  
Questions and Answers  
Q. Should I leave my Evolution amplifier on at all times?  
A. For maximum amplifier performance, leave the back panel power breaker  
switch on at all times. This places the amplifier in stand-by mode. Evolution  
amplifiers are designed to be powered on and off from stand-by, using the  
front panel power button. This eliminates “cold start” degradation. The amplifi-  
er will operate at full performance within minutes.  
Q. When I turn on the amplifier 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 all input and output connections and cables,  
making sure they are of sound construction. See Troubleshooting System  
Noise, on page 25. If the interconnects and cables are sound, you may be  
experiencing a ground loop. This can often be easily eliminated. Please con-  
tact your authorized Krell dealer, distributor, or Krell for suggestions on how to  
solve this problem.  
Q. My loudspeakers are rated for 150 Watts. Are the Evolution models too power-  
ful for them?  
A. No. A loudspeaker seldom is damaged from overdriving. More often, damage  
occurs when an amplifier that lacks sufficient power is asked to handle heavy  
demand situations such as high playback levels. These amplifiers may have  
very high 8 Ohm power ratings, but in heavy demand situations they can be  
driven into clipping (in which high power, high frequency harmonics go to the  
loudspeakers, due to loss of amplifier power). Clipping can damage loud-  
speakers. Avoid damage to your loudspeakers by reviewing your loudspeak-  
er’s specifications, and exercise caution in heavy demand situations.  
27  
 
Warranty  
Krell products have a limited warranty. Amplifiers, preamplifiers, preamp/processors,  
and receivers carry a limited warranty of five years for parts and labor on circuitry.  
Loudspeakers carry a limited warranty of five years for parts and labor. CD and  
DVD players carry a limited warranty of five years for parts and labor on circuitry,  
and three years for parts and labor on mechanical parts.  
Should the product fail to perform at any time during the warranty, Krell will repair it  
at no cost to the owner, except as set forth in this warranty.  
This warranty does not apply to damage caused by acts of God or nature.  
This warranty shall be in lieu of any other warranty, expressed or implied, including,  
but not limited to, any implied warranty of merchantability or fitness for a particular  
purpose. There are no warranties which exceed beyond those described in this  
document, if the product does not perform as warranted herein, the owner’s sole  
remedy shall be repair. In no event will Krell be liable for incidental or consequential  
damages arising from purchase, use, or inability to use the product, even if Krell  
has been advised of the possibility of such damages.  
IMPORTANT  
The single-ended inputs on the Evolution amplifiers are cap-coupled. Use these  
inputs whenever you are connecting a tube preamplifier.  
Proof of purchase in the form of a bill of sale or receipted invoice substantiating  
that the product is within the warranty period must be presented to obtain warranty  
service. The warranty begins on the date of the original retail purchase, as noted on  
the bill of sale or receipted invoice from an authorized Krell dealer or distributor.  
Previously owned equipment, when re-purchased from an authorized Krell dealer or  
distributor, has the balance of the original warranty, based on the original date of  
manufacture. Krell dealers and distributors are not authorized to sell current prod-  
ucts on the Internet. Current products purchased via the Internet do not have any  
transferrable warranty.  
The warranty for a Krell product is valid only in the country to which it was originally  
shipped, through the authorized Krell distributor for that country, and at the factory.  
There may be restrictions on or changes to the Krell warranty because of regula-  
tions within a specific country. Please check with your distributor for a complete  
understanding of the warranty in your country.  
continued  
28  
 
If the product is serviced by a distributor who did not import the unit, there may be  
a charge for service, even if the product is within the warranty period.  
Freight to the factory is your responsibility. Return freight within the United States  
(U.S.A.) is included in the warranty. If you have purchased your Krell product out-  
side the U.S.A. and wish to have it serviced at the factory, all freight and associated  
charges to the factory are your responsibility. Krell will pay return freight to the  
U.S.A.-based freight forwarder of your choice. Freight and other charges to ship the  
product from the freight forwarder to you are also your responsibility.  
Krell is not responsible for any damage incurred in transit. Krell will file claims for  
damages as necessary for a product damaged in transit to the factory. You are  
responsible for filing claims for shipping damages during the return shipment.  
Krell does not supply replacement parts and/or products to the owner of the prod-  
uct. Replacement parts and/or products will be furnished only to the distributor  
performing service on this product on an exchange basis only; any parts and/or  
products returned to Krell for exchange become the property of Krell.  
No expressed or implied warranty is made for any Krell product damaged by acci-  
dent, abuse, misuse, natural or personal disaster, or unauthorized modification.  
Any unauthorized voltage conversion, disassembly, component replacement,  
perforation of chassis, updates, or modifications performed to the product  
will void the warranty.  
The operating voltage of the product is determined by the factory and can only be  
changed by an authorized Krell distributor or at the factory. The voltage for this  
product in the U.S.A. cannot be changed until six months from the original pur-  
chase date.  
In the event that Krell receives a product for warranty service that has been modi-  
fied in any way without Krell authorization, all warranties on that product will be  
void. The product will be returned to original factory layout specifications at the  
owner’s expense before it is repaired. All repairs required after the product has  
been returned to original factory specifications will be charged to the customer, at  
current parts and labor rates.  
All operational features, functions, and specifications and policies are subject to  
change without notification.  
To register your product for warranty benefits, please complete and return the  
Warranty Registration Card enclosed in the shipping box within 15 days of pur-  
chase. Thank you.  
29  
 
Return Authorization Procedure  
How to Expedite Service  
If you believe there is a problem with your component, please contact your deal-  
er, distributor, 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:  
To contact the Krell Service Department:  
TELL  
203-298-4020, Monday-Friday  
9:00 AM to 5:00 PM EST  
203-795-2287  
FAX  
How to Return a Product  
To return a 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 or damage to the product during shipment  
to the Krell factory and ensure that all freight (shipping) charges are prepaid.  
The product may also be hand delivered if arrangements with the Service  
Department have been made in advance. Proof of purchase will be required for  
warranty validation at the time of hand delivery.  
IMPORTANT  
Use the original packaging to ensure the safe transit of the product to the factory,  
dealer, or distributor. Krell may, at its discretion, return a product in new packaging and  
bill the owner for such packaging if the product received by Krell was boxed in non-  
standard packaging or if the original packaging was so damaged that it was unusable.  
If Krell determines that new packaging is required, the owner will be notified before  
the product is returned.  
How to Purchase Additional Packing  
To purchase additional packing, please contact your authorized Krell dealer, dis-  
tributor, or the Krell Service Department for assistance.  
30  
 
Specifications  
Measurement  
Evolution 302 Stereo Amplifier  
Evolution 402 Stereo Amplifier  
FREQUENCY RESPONSE  
20 Hz to 20 kHz +0, –0.10 dB  
<0.5 Hz to 180 kHz +0, –3 dB  
20 Hz to 20 kHz +0, –0.18 dB  
<0.5 Hz to 120 kHz +0, –3 dB  
SIGNAL-TO-NOISE RATIO  
Wideband, unweighted, referred to full  
power output  
>107 dB  
>106 dB  
“A” weighted  
>117 dB  
25.5 dB  
>116 dB  
25.4 dB  
GAIN  
TOTAL HARMONIC DISTORTION  
<0.02% at 1 kHz, at 300 W, 8 Ohms <0.02% at 1 kHz, at 400 W, 8 Ohms  
<0.15% at 20 kHz, at 300 W, 8 Ohms <0.15% at 20 kHz, at 400 W, 8 Ohms  
INPUT IMPEDANCE  
Single-ended  
Balanced  
CAST  
100 kOhms  
200 kOhms  
75 Ohms  
100 kOhms  
200 kOhms  
70 Ohms  
INPUT SENSITIVITY  
Single-ended or balanced  
2.60 V rms  
3.04 V rms  
CAST  
2.60 mA rms  
3.04 mA rms  
OUTPUT POWER  
All channels driven  
300 W rms at 8 Ohms  
600 W rms at 4 Ohms  
1200 W rms at 2 Ohms  
400 W rms at 8 Ohms  
800 W rms at 4 Ohms  
1600 W rms at 2 Ohms  
OUTPUT VOLTAGE  
139 V peak-to-peak  
49 V rms  
160 V peak-to-peak  
57 V rms  
OUTPUT CURRENT  
SLEW RATE  
35 A peak  
37 A peak  
120 V/µs  
100 V/µs  
OUTPUT IMPEDANCE  
<0.040 Ohms at 20 Hz  
<0.055 Ohms at 20 Hz  
<0.053 Ohms, 20 Hz to 20 kHz  
<0.064 Ohms, 20 Hz to 20 kHz  
DAMPING FACTOR  
Referred to 8 Ohms  
>200 at 20 Hz  
>150, 20 Hz to 20 kHz  
>145 at 20 Hz  
>125, 20 Hz to 20 kHz  
POWER CONSUMPTION  
Stand-by  
Idle  
150 W  
320 W  
370 W  
570 W  
Maximum  
3400 W  
3800 W  
HEAT OUTPUT  
Stand-by  
Idle  
510 BTU/hr.  
1100 BTU/hr.  
5500 BTU/hr.  
890 BTU/hr.  
1300 BTU/hr.  
6400 BTU/hr.  
Maximum  
INPUTS  
2 single-ended via RCA connector  
2 balanced via XLR connector  
2 single-ended via RCA connector  
2 balanced via XLR connector  
2 CAST via 4-pin bayonet connector 2 CAST via 4-pin bayonet connector  
OUTPUTS  
2 pairs Krell binding posts  
2 pairs Krell binding posts  
DIMENSIONS  
17.3 in. W x 9.8 in. H x 20.7 in. D  
17.3 in. W x 9.8 in. H x 22.1 in. D  
438 mm W x 248 mm H x 525 mm D 438 mm W x 248 mm H x 550 mm D  
WEIGHT  
Shipping  
Unit only  
138 lb., 62.4 kg  
120 lb., 54.3 kg  
150 lb., 67.9 kg  
135 lb., 61.1 kg  
All operational features, functions, specifications, and policies are subject to change without notification.  
31  
 
(Specifications continued)  
Measurement  
Evolution 403 3-channel Amplifier Evolution 400 Monaural Amplifier  
FREQUENCY RESPONSE  
20 Hz to 20 kHz +0, –0.18 dB  
<0.5 Hz to 120 kHz +0, –3 dB  
SIGNAL-TO-NOISE RATIO  
Wideband, unweighted, referred to full  
power output  
>106 dB  
“A” weighted  
>116 dB  
25.4 dB  
GAIN  
TOTAL HARMONIC DISTORTION  
<0.02% at 1 kHz, at 400 W, 8 Ohms  
<0.15% at 20 kHz, at 400 W, 8 Ohms  
INPUT IMPEDANCE  
Single-ended  
Balanced  
CAST  
100 kOhms  
200 kOhms  
70 Ohms  
INPUT SENSITIVITY  
Single-ended or balanced  
3.04 V rms  
CAST  
3.04 mA rms  
OUTPUT POWER  
400 W rms at 8 Ohms  
800 W rms at 4 Ohms  
1600 W rms at 2 Ohms  
OUTPUT VOLTAGE  
160 V peak-to-peak  
57 V rms  
OUTPUT CURRENT  
SLEW RATE  
37 A peak  
100 V/µs  
OUTPUT IMPEDANCE  
<0.055 Ohms at 20 Hz  
<0.064 Ohms, 20 Hz to 20 kHz  
DAMPING FACTOR  
Referred to 8 Ohms  
>145 at 20 Hz  
>125, 20 Hz to 20 kHz  
POWER CONSUMPTION  
Stand-by  
Idle  
370 W  
570 W  
Maximum  
5000 W  
HEAT OUTPUT  
Stand-by  
Idle  
1270 BTU/hr.  
1950 BTU/hr.  
7700 BTU/hr.  
Maximum  
INPUTS  
3 single-ended via RCA connector  
3 balanced via XLR connector  
3 CAST via 4-pin bayonet connector  
OUTPUTS  
3 pairs Krell binding posts  
DIMENSIONS  
17.3 in. W x 9.8 in. H x 26.1 in. D  
438 mm W x 248 mm H x 662 mm D  
WEIGHT  
Shipping  
190 lb., 86 kg  
Unit only  
175 lb., 79.2 kg  
All operational features, functions, specifications, and policies are subject to change without notification.  
continued  
32  
 
(Specifications continued)  
Measurement  
Evolution 600 Monaural Amplifier Evolution 900 Monaural Amplifier  
FREQUENCY RESPONSE  
20 Hz to 20 kHz +0, –0.18 dB  
<0.5 Hz to 120 kHz +0, –3 dB  
20 Hz to 20 kHz +0, –0.18 dB  
<0.5 Hz to 120 kHz +0, –3 dB  
SIGNAL-TO-NOISE RATIO  
Wideband, unweighted, referred to full  
power output  
>110 dB  
>113 dB  
“A” weighted  
>119 dB  
25.4 dB  
>122 dB  
25.4 dB  
GAIN  
TOTAL HARMONIC DISTORTION  
<0.02% at 1 kHz, at 600 W, 8 Ohms <0.02% at 1 kHz, at 900 W, 8 Ohms  
<0.15% at 20 kHz, at 600 W, 8 Ohms <0.15% at 20 kHz, at 900 W, 8 Ohms  
INPUT IMPEDANCE  
Single-ended  
Balanced  
CAST  
100 kOhms  
200 kOhms  
70 Ohms  
100 kOhms  
200 kOhms  
70 Ohms  
INPUT SENSITIVITY  
Single-ended or balanced  
3.72 V rms  
4.55 V rms  
CAST  
3.72 mA rms  
4.55 mA rms  
OUTPUT POWER  
600 W rms at 8 Ohms  
1200 W rms at 4 Ohms  
2400 W rms at 2 Ohms  
900 W rms at 8 Ohms  
1800 W rms at 4 Ohms  
3600 W rms at 2 Ohms  
OUTPUT VOLTAGE  
196 V peak-to-peak  
69 V rms  
240 V peak-to-peak  
85 V rms  
OUTPUT CURRENT  
SLEW RATE  
49 A peak  
60 A peak  
100 V/µs  
90 V/µs  
OUTPUT IMPEDANCE  
<0.030 Ohms, 20 Hz to 20 kHz  
>270, 20 Hz to 20 kHz  
<0.023 Ohms, 20 Hz to 20 kHz  
>350, 20 Hz to 20 kHz  
DAMPING FACTOR  
Referred to 8 Ohms  
POWER CONSUMPTION  
Stand-by  
Idle  
260 W  
410 W  
440 W  
650 W  
Maximum  
3800 W  
5000 W  
HEAT OUTPUT  
Stand-by  
Idle  
890 BTU/hr.  
1400 BTU/hr.  
5500 BTU/hr.  
1500 BTU/hr.  
2200 BTU/hr.  
7700 BTU/hr.  
Maximum  
INPUTS  
1 single-ended via RCA connector  
1 balanced via XLR connector  
1 single-ended via RCA connector  
1 balanced via XLR connector  
1 CAST via 4-pin bayonet connector 1 CAST via 4-pin bayonet connector  
OUTPUTS  
1 pair Krell binding posts  
1 pair Krell binding posts  
DIMENSIONS  
17.3 in. W x 9.8 in. H x 22.1 in. D  
17.3 in. W x 9.8 in. H x 26.1 in. D  
438 mm W x 248 mm H x 560 mm D 438 mm W x 248 mm H x 662 mm D  
WEIGHT  
Shipping  
Unit only  
150 lb., 67.9 kg  
135 lb., 61.1 kg  
190 lb., 86 kg  
175 lb., 79.2 kg  
All operational features, functions, specifications, and policies are subject to change without notification.  
33  
 
EVOLUTION AMPLIFIERS  
302 AND 402 STEREO  
403 THREE-CHANNEL  
400, 600, AND 900 MONAURAL  
OWNER’S REFERENCE  
V08.0  
KRELL INDUSTRIES, INC.  
45 CONNAIR ROAD  
ORANGE, CT 06477-3650 USA  
TELL: 203-298-4000 • FAX: 203-891-2028  
 

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