Krell Industries Stereo Amplifier KSA 150 250 User Manual

KRELL,  
THE LEADER IN AUDIO ENGINNERING  
KSA – 150 / 250 OWNER’S MANUAL  
INTRODUCTION  
Thank you for your purchase of the new Krell KSA-150 or KSA-250 Power  
amplifier. The KSA-150 and 250 represent the absolute latest evolution in  
amplifier technology. They have many innovative design features in addition to  
Krell refined Class A power and direct-coupled circuitry from input to output.  
There are several aspects of the KSA-150 and KSA-250’s operation that require  
your special attention before installation. Because of the high level of  
performance capabilities of the KSA-150 and 250, careful placement and  
installation are crucial. Your thorough understanding of the operation and  
interrelation of your new amplifier with your audio system will ensure its  
maximum performance and long life.  
ABOUT THE OWNER’S MANUAL  
The Owner’s Manual is divided into various groups of information. The purpose  
of the manual is to familiarize you with the product and guide you through its set-  
up, installation and operation in a logical progression.  
TABLE OF CONTENTS  
A.  
B.  
General Information: A description of the basic design and  
performance features of the KSA-150 and KSA-250  
Power Considerations: Your new power amplifier and its electrical  
requirements  
C.  
D.  
Unpacking  
Installation: Cautions, unit location guidelines, and connection of inputs  
and speakers  
E.  
F.  
G.  
Operation  
Protection Circuitry  
Warranty and Service Information  
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protective action exists for a wide range of problematic conditions. Collectively,  
the protection circuitry is designed to avoid damage caused by other defective  
components, faulty wiring, mishandling of the system or amplifier failure.  
Krell is committed to balanced operation in all products. Balanced systems have  
long been standard in professional audio applications and the same advantages  
apply to home audio equipment. There is a 6dB increase in gain without an  
increase in noise and there is a decrease in overall system noise caused by stray  
AC and RF fields. Sonic performance is drastically improved, particularly in  
dynamic and soundstage presentation.  
B. POWER CONSIDERATIONS  
The KSA-150 is rated as delivering 150 watts per channel into 8 ohms. The  
amount of Class A power is adjusted for the finest sonic performance with a  
minimum of generated heat and energy consumption. The amplifier’s maximum  
power into 8 ohms is 220 watts per channel. The KSA-250 is rated as delivering  
250 watts per channel into 8 ohms. The amplifier’s maximum power into 8 ohms  
is 320 watts per channel.  
That every Krell product uses Class A circuitry in all gain and supply stages is a  
foundation of our design philosophy. A second design commitment that relates to  
amplifiers is that every unit be capable of doubling its output into successively  
lower impedances. The KSA-150 will deliver 300 watts per channel into 4 ohms,  
600 watts per channel into 2 ohms and 1,200 watts per channel into 1 ohm. The  
KSA-150 is fully capable of driving impedances below 1 ohm. The KSA-250 will  
deliver 500 watts per channel into 4 ohms, 1,000 watts per channel into 2 ohms  
and 2,000 watts per channel into 1 ohm. The KSA-250 is capable of driving  
impedances below 1 ohm.  
Given the above, the AC power supplied to the amplifier is crucial to getting  
maximum performance. The KSA-150 will operate at its peak with a dedicated  
20- amp line, although this is not a requirement. Additionally, the KSA-150 should  
only be operated with the power cord supplied with the unit. Use of other power  
cords may damage the amplifier and void its warranty. The KSA-250 requires a  
dedicated 20-amp line. It too, should only be operated with the power cord  
supplied with the unit.  
Please consult Krell or your dealer before using any devices designed to alter or  
stabilize the AC power for the KSA-150 or KSA-250.  
C. UNPACKING  
Remove the unit, power cord and accessories from the shipping container. Store  
all packing materials in a cool, dry place for future use. Inspect the unit for  
shipping damage. If any damage is evident, contact your dealer immediately. If  
the unit is in proper condition, proceed with the installation.  
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D. INSTALLATION  
1. CAUTIONS: These are important points of which you should always be  
aware.  
·
Do not connect the power cord into the AC mains before completing  
the entire installation.  
·
·
The unit must always be turned off while making connections.  
Krell XLR and custom RCA connectors are made to very exacting  
standards. Connectors of lesser quality may damage the amplifiers  
or cause poor connections. Please check with your dealer or Krell  
about the use of any other connectors.  
2. UNIT LOCATION GUIDELINES  
With the power cord disconnected from the AC mains, lay out the pre-amp to  
power amplifier interconnect and speaker cables to best determine the  
placement for the amplifier. As mentioned earlier, the KSA-150 operates at its  
peak with a dedicated 20-amp line and the KSA-250 requires a dedicated 20-  
amp line. Consult a licensed electrician for installation of a dedicated line.  
Amplifiers dissipate in heat much of the power they consume. The KSA-150 or  
KSA-250 must be installed in a location that provides unobstructed ventilation. If  
the units will be installed on shelving or in a cabinet, extra ventilation is  
necessary. This can be accomplished with the use of ‘whisper’-type fans in a  
variety of ways. Consult your dealer for assistance. Generally, with the front and  
rear of the installation shelving or cabinetry open, 8 inches of clearance on the  
sides and top of the amplifies should provide adequate ventilation.  
The dimensions of the KSA-150 are: 19” wide X 16.75” deep x 8.5” high. Add  
2.5” of depth for front and rear handles. The unit weighs 90 pounds. Shipping  
weight is 105 pounds. The dimensions of the KSA-250 are: 19” wide x 21.5” deep  
x 8.5” high. Add 2.5” of depth for front and rear handles. The unit weighs 140  
pounds. Shipping weight is 144 pounds.  
3. CONNECTION OF INPUTS AND SPEAKERS  
Note: The KSA-250’s AC power cord may be connected to the amplifier at this  
time, but do not yet connect the power cord to the AC mains.  
The KSA-150 and KSA-250 have both balanced and single-ended inputs. The  
balanced inputs use 3-pin XLR connectors and single-ended inputs use RCA  
connectors. The pin assignments for the XLRS are: pin 1 = signal ground: pin 2 =  
non-inverting input: pin 3 = inverting input. The RCA connector is wired in parallel  
with pin 2, the non-inverted input. Only one of these inputs should be  
connected to the preamplifier.  
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The input that is not connected to the preamplifier may be used as an output to a  
second amplifier for power bi-amp applications. Before proceeding with such an  
installation, you should consult your dealer or Krell.  
The KSA-150 and KSA-250 are shipped with shorting pins in the XLR inputs.  
These pins must remainin the XLR inputs if the units are to operate in the single-  
ended mode. These pins must be removed to connect either unit for balanced  
operation. The shorting pin connects pins 1 and 3 and grounds the inverted input.  
The wiring to and from the amplifier, and all components in general, should be  
arranged in a neat, organized manner. Specifically, AC wires should be  
separated from audio wire. This insures the avoidance of hum or the introduction  
of other unwanted noise into the system.  
It is always preferable to run long interconnect cables to the amplifier and to keep  
speaker cable length to a minimum. Speaker cable does add impedance  
between the speakers and the amplifier, regardless of the wire gauge. All Krell  
amplifiers will drive the lowest impedances with ease. When impedance is added  
in any significant amount, (for instance with excessive cable length) amplifier  
power is literally wasted in driving the cable, thereby reducing the maximum  
power that can be delivered to the speakers.  
The feet on the KSA-150 or KSA-250 can be used three different ways. They are  
made from machined Delrin and are supplied with separate rubber bottoms and  
mounting screws. The rubber bottom can be screwed into the Delrin for the  
protection of fragile surfaces such as hardwood floors or furniture. For use on  
rugs or carpeting, using the feet without the rubber bottoms is recommended.  
You may purchase, from your authorized dealer, a set of Acoustic Mass  
Dampers (AMDs). AMDs are custom-machined stainless steel feet fitted with a  
threaded insert and a washer made from acoustically absorbent material. When  
threaded into the Delrin feet, the AMS will decouple the amplifier from vibrations  
present on the surface where the unit is installed.  
Once the amplifier is in place, and turned off, you can begin to connect the  
interconnect and speaker cables. The preamplifier should be off, with the level  
fully attenuated (turned down). All other sources should be off. The two sets of 5-  
way binding posts for each channel’s output are wired in parallel to allow easy bi  
wiring.  
You may now connect the AC.  
E. OPERATION  
Activate the system by turning on the source components and preamplifier with  
the volume fully attenuated (turned down). The amplifier must always be turned  
on last. Just after turn-on, a soft click will be heard. This is the main power relay  
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closing. At this pint the amplifier’s outputs are not connected to the speakers.  
After the protection circuits detect that the unit has completely stabilized, the  
speaker relays will engage. Another click will be heard at this point. The amplifier  
is now ready to use. The amplifier will be at temperature and sound its best after  
approximately 15 minutes.  
Operation of the amplifier is simple. It is important to note that care must be  
taken in the operation of the whole system in relation to the significant power  
output of either amplifier. Mistakes, such as switching between active sources  
without muting the preamplifier output or bumping/miscuing a phonograph  
cartridge, can generate large transients at low frequencies. When this type of  
transient activity occurs, the amplifiers can generate enough power-surge to  
damage most loudspeakers. All switching of sources should be done with the  
preamplifier level either muted or fully attenuated (turned down). Inputs to the  
amplifier should never be changed while the amplifier is on.  
Care must be taken when setting high playback levels. Because of their  
tremendous reserve of clean power, Krell amplifiers safely drive speakers to  
higher sound pressure levels than other amplifiers. This often results in driving  
the speakers to their limit. Always turn the volume level down at the first sign of  
distortion.  
When turning off the system, the amplifier should always be first. This avoids the  
possibility of a turn-off transient occurrence from some other component to the  
speakers.  
F. PROTECTION CIRCUITRY  
The KSA-150 and KSA-250 have a sophisticated series of circuits that protect  
them from dangerous input signals or loads on the output. These circuits also  
analyze various amplifier functions to prevent speaker damage that may be  
caused if the amplifier fails to function properly.  
There are two protection modes: Input and Output. When the Input Protection is  
engaged the amplifier will remain on, with the front panel LED illuminated, but it  
will not pass a signal. This indicates a problem with the input signal caused by  
the preamplifier or source component. This is most often a DC condition. The  
amplifier will resume passing signal when the problem is resolved.  
When the Output Protection is engaged the amplifier will turn off, with the front  
panel LED turning off as well. This usually indicates a problem with the speaker  
wires, their connection, or the speakers themselves. Once the problem is located  
and resolved the amplifier will turn on normally with activation of the front panel  
switch. The Output Protection will also engage if the amplifier fails. If the amplifier  
will not turn on with all inputs and outputs disconnected, please contact your  
dealer or Krell Service.  
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IMPORTANT NOTES REGARDING PROTECTION CIRCUITRY  
1. When the Output Protection circuitry has been engaged, allow at  
least 20 seconds before turning on the amplifier again. Repeated  
fast cycling of the On/Off switch can damage the amplifier and void  
the warranty.  
2. If the amplifier does not come on following the procedure above,  
please contact your dealer.  
3. There is a circuit breaker on the amplifier real panel. This breaker  
protects the amplifier in the event of catastrophic failure. If the  
circuit breaker engages, contact your dealer or the Krell Service  
Department. Do not attempt to reset the circuit breaker.  
G. WARRANTY AND SERVICE INFORMATION  
There are no fuses or user-serviceable parts in the KSA-150 or KSA-250. Both  
amplifiers have a limited warranty of five years from the date of purchase for  
parts and labor. Return freight is included in the warranty. Please return the  
warranty car immediately after successful installation and operation are  
completed.  
The warranty for Krell products is valid only in the country to which they were  
shipped and at the Krell factory in Orange, Connecticut, USA. If there are  
problems with any of your Krell products, please contact your authorized Krell  
dealer or the Krell Service Department.  
Please do not return any unit to Krell without first having contacted the Krell  
Service Department and receiving a Return Authorization Number. Units should  
be shipped in Krell packing. Packing materials may be purchased through the  
Krell Service Department. Freight charges to the factory or distributor are the  
responsibility of the customer. Krell or the dealer/distributor will pay return freight  
charges on warranty repairs.  
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