Krell Industries 600, 300, 650M, 200, 250M Instructions For Use Manual

~The L~eade~r in A~udio Engineen’ng

Full Power Balanced
Power Amplifiers

600, 300, 200 Stereo
650M, 350M, 250M Monaural

Instructions for Use, v 98.2

Owner’s Reference

A note from Dan D’Agostino

Thank you for your pd~chase of a Full Power Balanced amplifier. This
component has been designed to exceed all other amplifier products in ultimate
performance, musicality, and overall durability. I am sure that it will give you
many years of superior performance. Some of the features that r[Lake this Full

Power Balanced amplifier unique include:

Kreil Current ModeTM: This advanced circuit topology is a KRELL

introduction to the audio industry and yields a far greater degree of speed

and stage presence than is possible through conventional technologies’.

Fully Regula-~ed Output Stage: One of the most obvious causes of musicat
corruption in an amplifier is voltage and current drop in the output stage.
While the large capacitive banks used by other manufacturers are marginally
effective with current drop, capacitors cannot compensate for voltage drop.

~, Full Power Balanced amplifier’s regulated output stage and power supply is

impervious to these forms of corruption. Current and voltage remain constant
under all operating conditions.

Balanced Amplifier Design: Your Full Power Balanced amplifier
incorporates completely balanced circuit topology from input to output,
maintaining the integrity of the audio signal and exercising greater speaker
control by means of its balanced, push-pull relationship with the speaker
drivers.

Class A Operation: Class A is the only linear operating state in electronics.
Your Full Power Balanced amplifier operates in Class A to its full rated power
to provide the most accurate and richly detailed musical experience possible.

Sustained Plateau Bias Ii~: Sustained Plateau Bias II

TM

is a KRELL
patented process that enables your amplifier to play all music (up to full rated
power) in Class A, yet greatly reduce the heat dissipation and energy

consumption associated with conventional Class A designs. Sustained

3

¯

Pla~teau Bias ii

TM

is a true Class A circuit, as opposed to sliding or adaptive

biasing schemes.

The Full Power Balanced amplifier follows all classic KRELL mar~ufaoturing and
materials requirements, and I am sure that you will not find its equal anywhere in
the world.

Enjoy your KRELL Full Power Balanced amplifier.

Sincerely,

Dan D’Agostino

C.E.O

4

Introduction

To obtain the best performance from your Full Power Balanced amplifier, careful

’attention should be paid to its placement, installation, and operation. A thorough

understanding of these details will help insure satisfactory operation and long

life for the Full Power Balanced amplifier and related system components.

This Owner’s Reference is divided into several sections, each designed to

perform a different function. As you read through the Owner’s Reference you

will become better acquainted with the features and functions that make the Full

Power Balanced amplifiers a superb value..A Troubleshooting section is
included with solutions to potential problems. Should you have any questions
or suggestions, please feel free to contact your authorized ~ealer or the KRELL
staff for assistance.

The Full Power Balanced series of amplifiers consists of three stereo amplifiers,

the Full Power Balanced200, 300, and 600, and the three monaural amplifiers,

the Full Power Balanced 250M, 350M, and 650M. Installation, connection, and

operation of all amplifiers in the series is identical; however, please note that two
Full Power Balanced 250M, 350M or 650M amplifiers are required for stereo
operation.

In the unlikely event that your Full Power Balanced amplifier should require
service, you wi!! be pleased to know that is backed by a comprehensive
Customer Satisfaction policy and one of the most advanced service facilities in
the industry. For detailed information on the terms and conditions of service,

please refer to the Warranty and Service section of this Reference, Warranty
Registration Card, or an authorized KRELL Dealer or Distributor.

Unpacking

After opening the box and removing the top layer of foam, the Full Power
Balanced amplifier and the following items will now be visible:

IEC 320 20 amp AC power cord
Owner’s Reference
Warranty card

NOTES:
If any of these items are not included, please contact your authorized KRELL

dealer or distributor.
Save all packing materials. If you must ship your Full Power Balanced amplifier

in the future, repack the unit in its original packing to prevent shipping damage.

5

Location

Place the Full Powe~ Balanced amplifier on a firm level surface away from dirt or
moisture. When using custom racks or cabinetry, keep in mind the weight and

ventilation requirements for these amplifiers. Ideally, the amplifier should be

placed as close to the speakers as possible. It is preferable to run long

balanced interconnect cables to the amplifier and keep the speaker cable
length to a minimum. Speaker cable adds impedance to the I-6ad the amplifier

must drive, regardless of the cable’s gauge. All KRELL amplifiers will drive the
lowest impedances with ease, but when impedance is added due to long cable
lengths, amplifier power is wasted in the cable. Long speaker cables reduce the
maximum power that can be delivered to the speakers.

Remote Installation

Some installations do not have adequate, space or flexibility to place the amplifier
close to the speakers. The Full Power Balanced amplifiers can be situated in a

room or space close to the speakers, but out of sight, .and turned On or Off from
the listening room. Intemally, a provision has been made allowing the amplifier
to be powered On from an AC wall receptacle and not from the front panel power
switch or optional remote control. We suggest mounting a standard wall switch

in the listening room that controls an AC power outlet dedicated to the power
amplifier. This arrangement can be provided by an electrician. Please contact
your dealer for assistance.

NOTE: Once AC power is applied, the front panel power switch and the remote

P.csntml pnw~r .~vifP.h =r=

Cabinetry Considerations

Class A operation offers tremendous sonic benefits. Unfortunately, traditional

Class A amplifiers dissipate a tremendous amount of heat. KRELL’s patented

Sustained Plateau Bias circuitry combats this characteristic and reduces the heat

output considerably. However, the Full Power Balanced amplifiers can still

become quite warm under normal operation. The Full Power Balanced amplifiers

should be installed in a location that provides unobstructed ventilation.

IMPORTANT: The ventilation gdds on the top of all Full Power Balanced
amplifiers need to be unobstructed at all times during operation. Do not place
flammable material on top of or beneath Full Power Balanced amplifiers. For

installations inside cabinetry, extra ventilation may be necessary. Make sure the

Full Power Balanced amplifiers have adequate air circulation. Generally, two
inches of clearance on each side of the amplifier and eight inches of clearance

above the amplifier will provide adequate ventilation. In more extreme instances,

-, small fans can aid in removing excess heat from internal spaces-. Contact your
dealer, distributor, or Kreil®for more information.

6

AC Power Considerations

For best performan¢-e, a dedicated AC power line rated at a minimum of fifteen
amps is recommended for each amplifier. For maximum power output, the Full
Power Balanced 300 and 600 amplifiers Should be operated from a dedicated
twenty amp AC power line. The Full Power Balanced amplifiers should only be
operated with the power cord supplied. Please consult KRELL.or your dealer

before using any devices designed to alter or stabilize the AC power for the Full

Power Balanced amplifiers.

Connections

CAUTION: The differential circuitry employed within the Full Power

Balanced aml~lifiers requires special attention when connecting speakers.
Be careful not to connect the negative speaker terminals together. Do not
connect the negative speaker terminals to ground, or attempt to bridge the
left and right channels together of the Full Power Balanced stereo

amplifiers.-Please contact KRELL: Industries for assistance.
Input and Output Connections

Caution: When making connections to this component or any other, make sure
the power amplifier is off and the preamplifier is in the mute or stand-by mode.

The widng 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 cables. This practice prevents hum or other unwanted

noise from being introduced into the system.

1. Connect the speaker cables to the amplifier’s output terminals.

The Full Power Balanced amplifiers utilize two custom sets of identical speaker
terminals for the each channel. This configuration makes cable connections and

biwiring simple. The speaker terminals only accept spade lugs. Bare wire,

banana lugs, or pins will not work. The red terminals are used for positive

connections and the blue terminals are used for the negative connections.

Either the upper or lower set of speaker terminals may be used with speakers

having one pair of binding posts. For biwiring, both sets of terminals should be

used. Consult your speaker’s instruction manual for biwiring connections.

CAUTION: Make sure all cable terminations are of the highest quality, free from

frayed ends, shorts, or poor solder connections.