Knoll Systems 21-K Owners manual

21K

Stereo Amplifier
Installation Instructions

Caution: To reduce the risk of electrical shock, do not remove

the cover (or back). No user serviceable parts inside. Refer to
qualified service personnel.

Warning: To reduce the risk of fire or electric shock, do not
expose this appliance to rain or moisture.

The lightning flash with arrowhead, within an
equilateral triangle, is intended to alert the user to the

presence of uninsulated “dangerous voltage” within
the products that may be of sufficient magnitude to constitute a
risk of electrical shock to persons.

The exclamation point within an equilateral triangle is
intended to alert the user to the presence of
important operation maintenance (servicing)

instructions in the literature accompanying the appliance.

v1.0

Precautions:

substantial power output capability. Certain precautions must be
taken to ensure proper operation.

1. Never expose the unit to moisture.

2. Never plug an input cable into the amplifier while the
amplifier is turned on.

3. Never apply the “thumb test” (touching the “hot” lead of
the input cable with your finger) to the tip of the input
cable or input jack of the amplifier. RF rectification
and/or hum will be created and could cause damage to
the loudspeakers. Knoll will not be responsible for

SAFETY INSTRUCTIONS:

WARNING: TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK, DO NOT EXPOSE THIS UNIT
TO RAIN OR MOISTURE

Read all the safety and operating instructions before connecting
or using this unit.

All warnings on the unit and in this operating manual should be
adhered to. All operating and use instructions should be
followed.

damage to the loudspeakers due to improper use of the
equipment.

4. Under no circumstances should the output terminals of
the amplifier be short-circuited.

5. Avoid restricting the airflow around the unit. Good airflow
is necessary to help insure proper operation.

6. Be sure that the loudspeakers connected can handle the
output power of the amplifier at the loudspeakers rated
impedance. The warranty on the amplifier does not cover
damage to loudspeakers that have inadequate power
handling capabilities.

7. Do not stack other system components or any other
materials directly on top of the unit. The heat dissipating
system of the amplifier depends on free-flowing air
around the chassis.

The amplifier is a wideband design with

Do not use this amplifier near water including near a bathtub,
swimming pool or hot tub.

This unit should be installed so that its location does not
interfere with proper ventilation. For example, don’t place the
amplifier on a bed, sofa, rug, or similar surface that may block
the ventilation openings; or place in a built-in installation such
as a bookcase or cabinet that may block the flow of air through
its ventilation openings.

The unit should be set away from heat sources such as
radiators, heat vents, or other devices (including amplifiers)
that produce heat.

The unit should be connected to a power supply outlet only of
the voltage and frequency marked on its rear panel.

The power supply cord of the unit should be unplugged from the
wall outlet when it is to be unused for a long period of time.

Care should be taken so that objects to not fall, and liquids are
not spilled, into the enclosure through any openings.

The unit should be serviced by qualified service personnel when:

• The power cord or plug has been damaged; or objects
have fallen, or liquid has been spilled into the unit.

• The unit has been exposed to rain, or liquids of any kind;
or the unit does not appear to operate normally, or
exhibits a marked change in performance.

• The amplifier has been dropped, or the enclosure
damaged.

To prevent electric shock, do not use the polarized plug with an
extension cord, receptacle or other outlet unless the blades can
be fully inserted to prevent blade exposure.

Introduction:

stereo power amplifier and congratulations on your choice. This
amplifier is specifically designed to be the best sounding
amplifier available anywhere. Our engineers and designers
spent years of pain staking research and testing to perfect the
sound quality. We hope you will appreciate this effort and enjoy
the amp.

Thank you for your purchase of a Knoll 21K

Unpacking: The carton and packing materials used in shipping

your new amplifier were specially designed to protect it from the
shock and vibration of shipping. We suggest that you save the
carton and packing materials to use if you move, or if the unit
ever needs to be shipped back to us for any reason. Should you
discover that your amplifier has been damaged during shipping,
please contact your dealer or Knoll immediately and request the
name of the carrier so a written claim can be made.

The right to a claim against a public carrier can be forfeited if the
carrier is not notified immediately in writing and if the shipping
carton and packing materials are not available for inspection by the
carrier. Save all packing materials until the claim is settled.

Placement

During normal home operation the amplifier will become warm.
However, there are instances during high-level playback into
low impedance speakers when the amplifier will become much
warmer than normal. To ensure the amplifier’s trouble-free
operation, it is necessary to provide adequate ventilation. Your
amplifier should be kept away from external sources of heat
such as radiators and hot- air ducts. The amplifier should never
be placed with other heat-producing components in a cabinet or
enclosure lacking free airflow. Do not stack other components
on top of your amplifier.

Rack mounting

A rack mount version of the 21K is available. For best operation
when rack mounting the 21k we suggest it be near the top of
the rack and have vented blank 1 rack space panels above and
below the 21k. For multiple 21k amps in one rack we suggest
spacing the amps 1 rack space apart and inserting a vented
blank 1-rack space panel between each amp.

Getting to know the rear panel

A. Audio Inputs

Use the INPUT jacks to connect the outputs of a
preamplifier, receiver with pre-out connections, CD
player, or other control devices.

B. Input Gain Controls
Use these to adjust the input gain of each channel.

C. Product Serial Number

Write this number in the space provided on page “” for
future reference.

D. Remote Trigger Input

Use the REMOTE TRIGGER jack to connect a compatible
preamplifier, source device, or other product with a
12VDC output (abut 35mA required).

E. Audio Outputs

This is an unbuffered line level output to other devices
such as another 21k amplifier.

F. AC Input

Use the included power cord to connect your amplifier to
an AC power source.

G. Speaker Outputs
Use the OUTPUT binding posts to connect the amplifier to

your speakers: red for positive, black for negative.

Connecting your amplifier

When making connections between any source components and
the amplifier, or when making connections to any speaker, be
certain that both the input devices and the amplifier are turned
off. Unplug all equipment before making any connections so that
there will be no unwanted signal transients that can damage
equipment or speakers.

Input connections

Connecting the 21K to your source equipment is
straightforward. Using the high-quality audio interconnect
cables, match the output channel designations on the rear of
your source equipment to the input jacks on the rear panel of
your amplifier that have the same channel name. When making
connections with RCA type plugs on interconnect cables, make
certain to gently, but firmly, insert the plug into the jack. Loose
connections can cause intermittent sound and may damage your
speakers. Some quality RCA plugs may be very tight, and it is
important to secure a proper connection between the
interconnection cable and the input jack.

Speaker connections

To ensure that the high quality signals produced by your
amplifier are carried to your speakers without loss of clarity or
resolution, Knoll advises that you use high-quality speaker wire.
Many brands of wire are available — the choice may be
influenced by the distance between your speakers and the
amplifier, the type of speakers you use, personal preferences,
along with other factors.

Regardless of the brand or type of speaker wire chosen, we
suggest that you use a wire constructed of fine, multi-strand
copper with a gauge of 14 or less (the lower the number, the
thicker the cable). Wire with a gauge of 16 may be used for
short runs of less than 12 feet. We do not recommend that you
use any wires with an AWG equivalent of 18 or higher due to
the power loss and degradation in performance that will occur.

To connect the amplifiers to your speakers, a pair of binding
posts is provided for each channel output. These posts will
accept bare wire, spade lugs, or banana type plugs. If bare wire
is used for the connections, strip approximately 1/2 inch to 3/4
inch of insulation from the end of each wire and carefully twist
the strands of each conductor together. Be sure not to cut the
individual strands or twist them off. All strands must be used for
optimal performance.

Correct polarity connections are important to maintain proper
speaker phasing. When speaker phasing is correct, all speakers
move in and out at the same time preserving the imaging of the
program material. Out-of-phase connections mean that some