Kenwood KA-8100 User manual

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INTRODUCTION
The purpose of this manual is to acquaint you
with the operating features of your new amplifier.
You will notice that in every detail of planning,
engineering, styling, operating convenience, and
adaptability, we have sought to anticipate your
needs and desires.
We suggest that you read this manual carefully.
Knowing how to set up your amplifier, to the best
advantage, will enhance your listening pleasure right
from the start. You will also become aware of the
ease with which you can adjust your amplifier to
meet your special requirements.
SERIAL NUMBER
Record your SERIAL NUMBER on the spaces
designated on the warranty card. You will find
the serial number on the back of the unit.
AFTER UNPACKING
After unpacking, we recommend you inspect
and examine the unit for any possible shipping
damage. If your unit is damaged or fails to operate,
notify your dealer immediately. If your unit was
shipped to you directly, notify the shipping com-
pany without delay. Only the consignee (the per-
son or company receiving the unit) can file a claim
against the carrier for shipping damage.
We recommend you retain the original carton
and packing materials to prevent any damage
should you transport or ship your unit in the fu-
ture.
PRECAUTIONS CONCERNING INSTALLATION
(a) Avoid locations subject to direct sunlight.
(b) Avoid high or low temperature extremes.
(c) Keep the amplifier away from heat radiating
source.
WARNING:
TO PREVENT FIRE OR SHOCK
HAZARD,
DO
NOT
EXPOSE
THIS
APPLIANCE TO RAIN OR MOIS-
TURE.
2 KA-8100(k)
AC VOLTAGE SELECTION
The
KA-8100
operates
on
110
~
120
volts
or
220
~
240
volts
AC.
Before
operating
the
unit,
make
sure
that
the
position
of
the
AC
Voltage
Selector
Switch
matches
your
line
voltage.
If
not,
it
must
be
changed
to
the
proper
setting
in
accord-
ance with
the
instructions
below.
Note:
Our warranty does not cover damage caused by excessive
line voltage due to improper setting of the AC Voltage
Selector Switch.
AC 110-120V~
are |. Remove screws and stopper plate.
2. Switch levers to opposite side.
3. Lock levers by attaching stopper
plate to opposite side screws.
220-240V~
AC 220V~)
1h
AC 110-120V~~
( (AC 120V~)
ar ( ) is European type.
Stopper
plate
©
aye
© 1 @
AC 220-240V~.
(AC 220V~)
AC VOLTAGE SELECTOR SWITCH

FEATURES:
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GUIDE
TO
SAFETY
USAGE
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4
GENERAL
NOTES
FOR
CORRECT
USAGE
.......
4
INTERCONNECTING
DIAGRAM
.............4--
5
CONNECTING
INSTRUCTIONS
.......----.-5-
6
CONTENTS
CONTROLS
AND
THEIR
FUNCTIONS...........
10
OPERATING
INSTRUCTIONS
...........----5-
12
POINTS
TO
BE
CHECKED
PRIOR
TO
SERVICING
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14
SPECIFIGALIONS
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15
FEATURES
1. DC POWER AMPLIFIER
Although an ordinary amplifier is generally provided
with input or interstage capacitors, the KA-8100 power ampli-
fier section does not have any input or interstage capacitors.
In addition, the NF loop circuit also does not have any
capacitor that may be accompanied with a time constant.
Therefore there is no phase difference throughout the fre-
quency range including the super-low-frequency zone. Since
the DC power amplifier is almost free from distortion,
excessive distortion, rising time, etc., it offers extensively
improved sharpness and depth of sound as well as gorgeous
dimensional feeling.
Resolution is very good even at a low sound level, and
there is no oppressive sensation at a high sound level. This
amplifier assures highly qualified reproduction.
2. TWO INDEPENDENT POWER SUPPLIES
The KA-8100 uses the equivalent of two separate mono-
phonic amplifiers, each with its own power supply. This
arrangement completely eliminates the occurrence of dy-
namic crosstalk which is considered to influence the quality
of sound rigorously.
In particular, the power supply for the preamplifier
section employs exclusively designed transistorized regula-
tors to remove a mutual interference between former and
latter stages of the amplifier.
3. ICL EQUALIZER WITH CONSTANT-
CURRENT MIRROR LOAD FET
DIFFERENTIAL CIRCUIT
This is a 3-stage direct-coupled ICL circuit consisting
of the constant-current bias current mirror load differential
circuit, the class A constant-current load Darlington circuit,
and the pure complementary SEPP circuit. The use of
low-noise circuit elements and the optimum selection of
circuit constants assure excellent performance character-
istics such that the phono S/N ratio is 85 dB (IHF A), the
distortion factor is 0.003% (20 Hz ~ 20 kHz REC OUT),
and the RIAA deviation is +0.2 dB.
4. LOW DISTORTION, HIGH S/N RATIO
TONE CONTROL CIRCUIT
A tone control circuit is necessary to correct the
acoustic response of reproduced sound which may be affect-
ed by the room acoustics. However, ordinary tone control
circuit produces more distortion than any other element
in the amplifier. Kenwood solved this problem by using
FET differential amplifier in the first stage of the amplifier,
as well as baxandal tone control to circuit to reduce the
unwanted distortion and noise to negligible level.
5. FULL RANGE OF STEEP-SLOPE FILTER
The low frequency filter, effective from 40 Hz and
below at a slope of 12 dB/oct and subsonic filter with a
slope 6 dB/oct below 18 Hz reduces turntable rumble or
other low frequency interference without materially affect-
ing musical response, while at high frequency filter effec-
tive above 8 kHz with slope of 12 dB/oct helps to reduce
record scratch or other high frequency interferences.
6. SPECIAL TAPE-THROUGH CIRCUITRY
The KA-8100 has facilities for simultaneous recording
by two recorders and for dubbing, either from deck A to
B or vice-versa.
In addition, Kenwood’s tape-through circuitry allows
you to dub while listening to a different program source.
This may not be a feature you will use every day, but it is
quite practical and will be appreciated when the occasion
arises.
7. GAIN CONTROL
The gain in flat amp can be switched to +10 dB, 0,
—10 dB. It works as a normal attenuator and direct play-
back is possible with a low output type cartridge when set
at the +10 dB position.
8. ACCURATE VOLUME CONTROL
EXPANDS FINE ADJUSTMENT
The volume control is equipped with a precision atten-
uator of the type employed in measuring instruments and
other high reliability equipment. Volume adjustment can
be easily performed when listening at low volume levels,
temporarily reducing the volume, or employing a low input
level (high gain) power amplifier. The volume adjustment
range can also be expanded by employing the volume con-
trol and gain control switch in combination.
9. LOUDNESS CONTROL WITH 3-LEVEL,
2-FREQUENCY CHANGE-OVER FEATURE
This loudness control assures very wide and fine adjust-
ments for the compensation of the sound field, acoustic
feeling, and low-frequency performance of the speaker sys-
tems.
10. Kenwood’s excellence of design and superior crafts-
manship is evident not only in the electronics of the KA-
8100 but also in all the controls.
KA-8100(K) 3

GUIDE TO SAFETY USAGE
HANDLING OF POWER PLUG
When you connect or disconnect the power
plug from the wall outlet, never do it with wet
hands to avoid unexpected accident from electric
shock. Hold the power plug itself when you pull
it out of the outlet. It will be a good habit if you
pull out the power plug before you leave your
house for a long time.
POWER CORD
The power cord must not be pulled strongly,
nor bent forcibly, nor extended by connecting an
extra cord. This will damage the cord and be a
cause of electric shock and a fire.
PREVENTION OF INTRUSION OF METALLIC
SUBSTANCE IN UNITS
The case top is provided with ventilation holes.
Never close these holes with ornamental cloth, etc.
Be careful not to put a coin, hair pin, needle, etc.,
into the unit through the holes. Otherwise, it may
be a case of malfunction and electric shock. Such
trouble is often caused by infants.
PREVENTION OF MODIFICATION
Each unit is shipped after passing careful
adjustments to the optimum operating conditions.
The unit interior must not be modified. Some
parts of the interior are applied with high voltage.
Never dismantle the case and touch the internal
parts. Only the qualified servicemen are in charge
of check-in the interiors.
GENERAL NOTES FOR CORRECT USAGE
NEVER HINDER THE AMPLIFIER FROM
VENTILATION
e In order to prevent internal temperature rise,
the amplifier case is provided with ventilation holes.
Therefore, the amplifier should be installed at least
1-31/32"" (5 cm) distant from other things.
The ventilation holes must not be closed by curtain,
table cloth, etc.
e If generation of a large output power for a
long time is attempted, the amplifier must not be
installed in stacks with other units. The tuner and
the amplifier should be installed side by side. If
there is no ample space for installation, then the
amplifier must be installed in the highest position.
PROTECTION OF SPEAKERS SYSTEM
@ Lower the sound volume when switching the
amplifier on or changing over the program source
to another. You should make it a rule to move the
4 kKA-8100(K)
volume control knob to a low sound level before
you turn the POWER switch on. Sudden feeding
of a large input power may damage the speaker
systems. If you keep such a habit, the speaker
systems can be protected against the attack of
violent noise occurring when a stylus is put ona
disk or an FM station is selected.
e Always pay attention to the permissible input
for the speaker systems in operation. If the sound
volume exceeds the permissible levels, the speaker
systems may be destroyed.
PRE OUT POWER IN TERMINAL
e Exactly insert the two short pin plugs into
the connectors between the pre-amplifier and the
power amplifier, located on the amplifier rear panel.
No sound is generated if these plugs are left dis-
connected.

INTERCONNECTING DIAGRAM
TURNTABLE | TAPE DECK A SPEAKER SYSTEMS A SPEAKER SYSTEMS B
RIGHT LEFT RIGHT
mn
(e)
LEFT
O) UN
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at
.
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In
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WUHAN
+ a
SPEAKERS(A.B4~
— A+
| OF [)
160 At88~160)
- B+
INPUT TAPE——-——
RIGHT LEFT RIGHT LEFT
_
BOS)
“9
OD
D
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PHONO
ie
EY
TUNER
at
@
*
@)
@
To AC OUTLET
RAIL RAL
LINE IN LINE OUT
(| ss) GS.
i weueme 002Ou:
TUNER TAPE DECK B
AC OUTLETS
2. UNSWITCHED outlet
The
AC
outlets
on
the
rear
panel
of
the
ampli-
This
outlet
delivers
power
at
all
times.
fier may be used to supply power to other com- (The capacity is 250 watts maximum.)
ponents such as‘a turntable, tape deck, etc. Aiotad:
1.
SWITCHED
outlets
1.
Units
shipped
to
the
European
countries
are
not
equip-
These
outlets
are
controlled
by
the
POWER
ped
with
the
AC
OUTLETS.
switch
on
the
front
panel.
(The
total
capacity
2.
Do
not
connect
any
equipment
whose
power
consump-
:
.
i
i
tlet.
is
100
watts
maximum.)
tion
exceeds
the
capacity
of
each
ou
KA-8100(K) 5

CONNECTING INSTRUCTIONS
SPEAKER CONNECTING AND SPEAKER
SWITCH
In connecting only one pair of speakers con-
nect the right speaker to ‘“RIGHT” and the left
speaker to “LEFT” of SPEAKERS A terminals.
Should (+) or (—) of either right or left channel be
reversely connected, sounds at the center section [
will be adversely affected by lack of separation. | | Omm
To connect an additional pair of speakers, connect
the right speaker to ‘“RIGHT” and the left speaker
to “LEFT” of SPEAKERS B terminals.
When connecting the speaker leads to the
speaker terminals, make sure that the bare wire
strands at the ends of the speaker leads do not
touch the adjacent terminal.
It is recommended that the tips of the speaker
leads are soldered, or the strands of individual leads
are twisted together to eliminate any possibility
of short-circuits forming in the speaker connecting
network.
NN a@ Remove insulation
= from wire end.
Note:
When only one pair of speakers are used, please ensure that
the impedance of each speaker is 4 ohms or more.
Loosen the Insert the Tighten the
When two pairs of speakers are used at the same time (A+B), screw wire screw
e that the impedance of each speaker is 8 ohms
please ensure tha peda p 8 f
or
more.
PHASING OF THE SPEAKERS
Speaker phasing can be determined in the following manner:
1. Set the MODE switch to MONO.
2. Set the INPUT SELECTOR switch to PHONO 1, and adjust the VOL-
UME control to the desired listening level.
3. Play a familiar record.
4. \f the sound comes directly from the front, the speakers are in phase.
If the sound comes from both sides and there is a noticeable loss
in low frequencies, the speakers are out of phase. In this case reverse
the leads on one speaker.
SPEAKER TERMINALS
TET] (RIGHT)
6 KA-8100(k)

CONNECTING
IN
STRUCTIONS
TURNTABLE CONNECTION
The two shielded audio cables from your
stereo turntable are normally terminated with
phono plugs. Connect the left channel of the turn-
table to the ‘‘LEFT’’ PHONO 1 input jack and the
right channel to the ““RIGHT’’ PHONO 1 input
jack.
If an additional turntable is used in order to
operate two turntables or two tonearms on the
same turntable, connect the left channel to the
“LEFT” PHONO 2 input jack and the right chan-
nel to the ““RIGHT’’ PHONO 2 input jack.
If the turntable has a grounding wire, connect
it to this amplifier’s GND terminal to avoid hum.
TAPE DECK CONNECTION
Recording
A tape deck can be connected for recording
as follows: left channel input of the tape deck to
TAPE A “LEFT” REC jack, right channel input
of the tape deck to TAPE A “RIGHT” REC jack.
Playback
A tape deck can be connected for playback
as follows: left channel output of the tape deck to
TAPE A “LEFT” PLAY jack, right channel output
of the tape deck to TAPE A “RIGHT” PLAY jack.
If an additional tape deck is used and two
tape decks are operated simultaneously, the same
connections must be provided for TAPE B jacks.
DIN CONNECTOR (REC/PLAY CONNECTOR)
If your tape deck is equipped with a DIN
connector, connect it to the ‘““TAPE B’”” REC/PLAY
connector with a DIN connecting cord. A DIN
connector enables recording and playback with
this single cord.
Notes:
1. Please note that the REC/PLAY connector corresponds
to the TAPE B REC and TAPE B PLAY jacks — the
signal must be controlled with TAPE (MONITOR) switch
on the front panel.
2. When a DIN cord is connected, the TAPE B PLAY and
REC jacks should not be used.
TURNTABLE
TAPE DECK
Rec REC/PLAY
TAPE
RIGHT LEFT |
KA~8100(K) 7

CONNECTING INSTRUCTIONS
TUNER CONNECTION
Use the TUNER terminals for connection to
an FM stereo or AM-FM stereo tuner.
Connect the left channel of the tuner to the
“LEFT” TUNER input jack and the right channel
of the tuner to the “RIGHT” TUNER input jack.
AUX (AUXILIARY INPUTS)
High level AUX input jacks are for miscel-
laneous sources, such as extra tape decks, additional
tuners and/or receivers, TV sound outputs, and
other external components.
TUNER
RIGHT A\LEFT
TECHNICAL DESCRIPTION
DC Power Amplifier
In many ways the direct current (DC) amplifier
is the ideal amplifier for audio use.
Kenwood audio engineers have taken up the
challenge of producing this ideal amplifier. The result
has been success in producing a power amplifier which
makes this dream come true.
Characteristics of DC Amplifier
1. They make reproduction of low frequencies
down to subsonic and DC levels possible.
The result is to give a greater sense of power in
the audio reproduction which greatly increases
enjoyment of music and reproduces the low-
frequency high-energy sounds of a live perform-
ance as only a DC amplifier can. .
2. There is zero phase difference between input
and output.
Because there are no capacitors in the signal path
to cause phase rotation, phase distortion is
absent.
3. Output waveform is a faithful duplication of the
input waveform. Although this would seem to
be a natural prerequisite for a hi-fi amplifier, it
is a fact that only a DC amplifier makes faithful
duplication possible.
8 KA-8100(K)
The performance of aDC amplifier depends upon
the stability of each individual circuit within it. In
the input stage, special dual FETs are used, intended
for the most demanding electronic computer applica-
tions (in packs of perfectly balanced pairs). This is
followed by a three-stage differential amplifier operat-
ing in Class A, in which the open loop gain is high,
and in which a fully adequate degree of negative
feedback is applied with a pre-driver load circuit in
which the power transistor bias is stabilized by a
constant current supply circuit. This circuit config-
uration gives excellent stability and extremely wide
frequency response.

CONNECTING
INSTRUCTIONS
PRE OUTPUT POWER IN JACKS
Independent Preamplifier/Power Amplifier
System
By utilizing these jacks, the KA-8100 can be
used
independently
to
drive
an
external
power
amplifier or preamplifier. This allows comparison
listening
between
the
KA-8100
power
amplifier
and
a
homebuilt
or
other
separate
power
amplifier.
And
also an external preamplifier can be connected to
the KA-8100 power amplifier section to compose
a
stereo
system.
In
such
a
case,
first
the
power
switch
off,
then
remove
the
short
pin
plug.
KA-8100
PRE AMP POWER AMP
i ee
ee
RIGHT LEFT
A Multi-amplifier System
By adding an electronic crossover network and
one or two additional power amplifiers, a high-
grade multi-amplifier system can be built in the
following manner.
1. Connect the PRE OUT jacks to the input jacks
of the crossover network.
2. Connect the POWER IN jacks to the low range
output jacks of the crossover network.
3. Connect the HIGH range output jacks of the
crossover network to the input jacks of a
separate power amplifier for the high fre-
quency range.
4. Connect the speakers for the lower frequencies
to the amplifier, and those for the higher fre-
quencies to the separate amplifiers.
Note:
For further details on connections, etc, see the instruction
manual supplied with the adaptor.
POWER AMP
INPUT.
q.
q:
MV
CROSSOVER
oes | NETWORK
AG,
ee
one
<n
==
GN POWER
PRE AMP
of
KA-8100
POWER AMP
re =
POWER AMP Speakers
High-mid Range
MV
Woofer
KA-8100(K) 9

CONTROLS AND THEIR FUNCTIONS
SPE OKERS.
() SPEAKERS switch
OFF — This position silences all speakers for private head-
phones listening.
A — Activates. speakers connected to the ‘‘A” speaker
terminals on the rear panel.
B — Activates speakers connected to the ‘’B”’ speaker
terminals on the rear panel.
A+B — Activates simultaneously two sets to speaker sys-
tems connected to the “A” and ““B”’ speaker terminals.
(2) POWER switch .
ON —_ This position turns the amplifier on. The pilot
lamp lights when the power is on.
OFF — This position turns the amplifier off.
@) PHONES jack
Plug stereo headphones into this jack. For private listen-
ing through headphones, set the SPEAKERS switch to the
OFF position.
@ TONE controls
The BASS and TREBLE controls are for adjusting the
bass and treble response. This is a click stop type control
graduated by 1.5 dB. Each knob controls both left and
right channels equally. Turning the knobs clockwise in-
creases bass and treble response and counterclockwise de-
creases bass and treble response.
You can select the bass and treble TURNOVER frequencies
(150 Hz or 400 Hz for bass control, 3 kHz or 6 kHz for
treble control) with the TURNOVER switches.
OFF position provides completely flat frequency response
with tone control circuit deactivated.
Switch positions and functions are as follows:
150 Hz: +7.5 dB at 50 Hz, 3kHz: +7.5 dB at 10 kHz
400 Hz: +7.5 dB at 100 Hz, 6 kHz: +7.5 dB at 20 kHz
1Q KA-8100(k)
(6) GAIN control
Set to —10 dB to attenuate the output by 10 dB. For
example, with GAIN set at —10 dB and VOLUME at —22
dB, it means that this amplifier is operating at —32 dB
gain below its rated level.
This position (—10 dB) can also be used to briefly lower
the volume when changing records or tapes. Set to +10
dB to boost the output by 10 dB.
© BALANCE control
This BALANCE control (Outer knob) adjusts unequal
volume from any program source in right and left channels.
The left channel is accentuated when this adjuster is turn-
ed from center toward the left side, and conversely.
@ VOLUME control
Adjust output level to speakers and headphones. Scale is
graduated in dB, and when used in conjunction with the
GAIN control, finer and wider range attenuation can be
performed.
LOUDNESS control
This switch is used for the compensation of the sound
- field and speaker performance, and also for the correction
of acoustic feeling in low-frequency zone when a source
is reproduced at a low sound level.
Since both low frequency and level can be controlled inde-
pendently, quite exquisite adjustments are possible in ac-
cordance with the conditions of the speaker systems and
the listening room. The relationship between switch posi-
tioning and function is shown in the following diagram.
If the frequency knob is in off position, the frequency
characteristic is completely flat and loudness control be-
comes ineffective.