Yamaha PC2002 User manual

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PROFESSIONAL
SERIES
POWER
AMPLIFIER
PC2002/2002M
OPERATING MANUAL
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YAMAHA

ABOUT THIS MANUAL
SCOPE
The PC2002M is a system oriented amplifier, made to be
used in conjunction .with mixers, consoles, frequency
dividing networks and speakers — those made by Yamaha
or by other manufacturers. Like any power amplifier, the
PC2002M’s performance depends on system design and
installation, in addition to its own capabilities. Thus, the
PC2002M Operating Manual is system oriented, describing
system design parameters and installation techniques, as
well as operation and performance of the PC2002M.
ORGANIZATION
We recommend that you read the entire Operating Manual.
However, if you are using the PC2002M in an existing
system, and you are familiar with high power amplifiers,
the BRIEF OPERATING INSTRUCTIONS, Pages 2 & 3,
contain all the information necessary for basic connections
and operation.
NOTE: The PC2002 is identical to the PC2002M except
there are no Peak Reading Meters.
CONTENTS
1МТВОООСТОМ......................... 1
BRIEF OPERATING INSTRUCTION ........... 2,3
GENERAL SPECIFICATIONS ................ 4
PERFORMANCE GRAPHS .................. 5,6
A DISCUSSION OF SPECIFICATIONS ........ 7~9
MOUNTING ......... SW exp A M oe E 10
BLOCK DIAGRAM ....................... 11
DIMENSIONS .................. а 12

INTRODUCTION
The PC2002M is not just "another big amplifier”, it is an
exciting new approach to high power sound. Yamaha's
leadership is clearly demonstrated by the PC2002M's pro-
fessional features, sophisticated design, and uncompromis-
ing performance. | :
PEAK READING METERS*
Instead of the more common and slow responding VU
meters, the PC2002M has PEAK READING METERS that
accurately display a full five decades (50dB) of output
level. The peak meters have large, illuminated faces marked
with dB and with watts into 8 ohms. The fast responding
meters provide a better way to see the program dynamics,
the transient power demands placed on the system, and the
available headroom. By indicating headroom, the meters
help the operator avoid over-driving the system, thereby
preventing the “clipped” waveforms so dangerous to drivers
and loudspeakers. :
CALIBRATED INPUT ATTENUATORS
The PC2002M has log-linear INPUT ATTENUATORS to
complement its peak reading meters. The input attenuators
are marked in 20dB-calibrated. steps, detented for extra
accuracy. The attenuators provide a smooth, noise free
transition from the highest to the lowest audio level. dB-
calibrated input attenuators have numerous advantages: on
the road, they allow predictable and repeatable setups; in
commercial sound applications, they allow easy, accurate
input sensitivity adjustments; in studios or discos, they let
operators simultaneously adjust the level of two channels
(or two programs on separate amplifiers) with precise track-
ing.
INPUT AND OUTPUT CONNECTIONS
INPUT CONNECTORS for each channel include one
“male” and one "female" XLR connector (BALANCED)
plus two parallel phone jacks (UNBALANCED). This
provides the flexibility necessary for convenient bridging to
another amplifier, as well as for adapter-free connection to
almost any mixer,
MONAURAL OPERATION
The PC2002 and PC2002M can easily be adapted for
monaural (BTL) operation by setting the rear-panel MODE
switch to MONO. In the MONO mode use the channel A
input connectors and channel A attenuator for level
control. The "+" terminal of the speaker system is con-
nected to the channel А “+” output terminal and the “—’’
terminal of the speaker system is connected to the channel
B "+" output terminal. Leave the channel A and B "—"
output (SPEAKER) terminals and channel B input
terminals unconnected.
SPEAKER IMPEDANCE IS 16 — 32 OHMS FOR:
MONO MODE OPERATION..
POUR LE MODE MONAURAL — L'IMPEDANCE
DES HAUT-PARLEURS EST 16 — 32 OHMS.
MODE
ое
STEREO МОМО
INPUT channel. A
PERFORMANCE
The
PC2002M’s
performance
is
as
impressive
as
its
features.
At
a
sustained
output
of
240
watts
into
8
ohms
(for
each
channel),
there
is
plenty
of
punch
to
reproduce
the
power-
ful
peaks
essential
to
clean
studio
monitoring.
High
power
handling
also
makes
the
PC2002M
an
unbeatable
choice
for
live
rock
or
disco
sound
systems,
where
an
amplifier
can
really
“cook”
all
night
long.
Power
alone
is
no
virtue;
the
PC2002M
has
ultra-low
distortion,
less
than
0.0596
THD
at
full
rated
power
—
the
kind
of
low
distortion
that
is
un-
detectable
by
even
the
most
critical
listeners.
A high damping factor of better than 350 at 1kHz reduces
the tendency for speaker cone overshoot, giving tighter and
better
defined
bass
response.
On
the
other
end,
the
PC2002M's frequency response extends well beyond
50kHz, enabling it to accurately reproduce the most
complex musical waveforms — even the tortuous output of
today's
synthesizers.
However,
high
frequency
response
has
not been achieved at the expense of stability; in fact, the
PC2002M
is
rock
steady.
Even
when
connected
to
highly
reactive
multi-speaker
loads,
there
is
no
tendency
to
shut
down or “take off” into spurious oscillation.
MECHANICAL CONSIDERATIONS
The PC2002M is constructed to withstand the high "G"
forces encountered on the road. Its solid front panel
mounts in any standard 19-inch rack, and, for a large
amplifier, the PC2002M weighs a modest 44 pounds
(20.5kg).** Front panel controls and meters are recessed to
avoid damage or accidental setting changes, and are further
protected by a pair of sturdy carrying handles. Inside and
out, the PC2002M is extremely reliable. Still, should service
ever be required, the unit is designed for easy access.
Massive side-mounted heat sinks are designed for efficient
cooling, making fans unnecessary in all but the most severe
thermal operating conditions. Four. non-conductive feet
ensure proper air flow when the amplifier is shelf mounted,
and avoid inadvertent ground loops. Multiple protection
circuits make the amplifier nearly abuse proof and
eliminate the need for troublesome DC power supply fuses.
* The PC2002 does not have the Peak Reading Meters.
** The PC2002 weighs 44 pounds (20kg)

BRIEF OPERATING INSTRUCTIONS
e
Front panel ө
Rack Handle
THERMAL
PROTECTION
CHB
Rack Handle
| : |
"ew | | | 5 50 зоо
in N | ПИР
ДЕҢ
4
ҮР,
PEAK ағ
WATTS ДИ ө
soo) 10 60 50 по ;
f \ Мур 2
5
POWER
PUSH ON/PUSH OFF
YAMAHA
PROFESSIONAL SERIES
POWER AMPLIFIER MODEL
@ POWER Switch/Indicator
Pressing this switch turns power to the amplifier ON and
causes the power indicator to light. Pressing the POWER
switch a second time turns the unit OFF.
@ THERMAL Indicator
This indicator lights if surface temperature of the main heat
sink exceeds 85 + 5 degrees centigrade.
Ө PROTECTION Indicator
Lights for approximately 4 seconds after power is switched
on, indicating that the protection circuitry. is active. The
speaker outputs are shut off while this indicator is lit. If the
protection circuitry is activated for any reason during
amplifier operation, the indicator will light and the speaker
outputs will be shut off. Once the cause of protection
activation
has
been
remedied
normal
operation
will
resume
automatically and the protection indicator will go out.
Ө) PEAK Level Meters (PC2002M)
These
meters
have
a
rise
time
of
10
milliseconds.and
a
fall
time
of
0.8
seconds.
The
logarithmic
meter
scales
read
directly
in
watts
when
speaker
impedance
is
8
ohms.
A
dB
scale
is
also
provided
with
O
dB
referenced
at
100
watts.
211908 "RU
ust ба в‘
~ a? s
CHANNEL А CHANNEL В .
9
an
8
@ Accessories
Fig. 1.
© CLIP Indicator |
The
CLIP
indicators
light
when
output
distortion
of
the
respective
channel
exceeds
approximately
2%.
This
indicates
that
the
amplifier
is
clipping
due
to
excessive
input
signal
levels.
|
*The
PC2002
CLIP
indicators
are
located
above
the
input
attenuators.
О Zero Adjust (PC2002M)
A small “*—'' screwdriver is used to adjust the peak meter
zero point.
@ Input Attenuators
The controls are detented in 21 dB steps, each step cor-
responding to 1 dB of attenuation except the last step.
Attenuation in the fully clockwise position is О dB, and
co in the fully counterclockwise position.
Q Knob Lock Adaptors (Supplied)
The
Knob
Lock
Adaptors
prevent
accidental
alteration
of
attenuator
settings
once
the
appropriate
settings
have
initially
been
made.

Веаг рапе!
Cord Reel
|)
SIEREO МОМО
МАХАМ
SP MRIG
USED.
CAUTION то REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE
COVER HO USER SERVICEABLE PARTS INSIDE PROT LAMP SOLOERED IN PLACE.
REFER SERVICING TO QUALIFIED SERVICE PEAS
ATTENTION afin DE RÉOUIRE LE RISQUE Hi ЕЗ EON. Ms
ENLEVER LE COUVERCLE. IL NE ЗЕ TROUVE A СМТЕВЕУЯ Al
POUVANT ETRE БЕРАНЕ PAR LUSAGER. LA LAMPE, ТЄМОН EST SOUDGE EN
PLACE.SAORESSEA А UN REPARATEUR- СОМРЕТЕ!
WARNING то nebuce тне Te О OF FIRE. г сию ‘SHOCK, DO мог
EXPOSE THIS APPLIANCE TO RAN ОН MOISTURI
CAUTION то ЕЕ due
FISK OF FIRE, REPLACE
чат SAME TYPE FUSE, 0
ATTENTIONS эни DE А RÉDUnE
LE RISQUE DE FEU, REMPLACE!
LUNQUEMENT PAR VW FUSLE
PRIMARY {е
7A 1250
«95,
х
US 4 Canadian models
YAMAHA
General model
@
SPEAKER
Output
Terminals
Fig.
2
The
red
SPEAKER
terminal
is connected to the
“+” input
©
Standard
Phone
Jacks
terminal
of
the
speaker
system
used
and
the
black
These
jacks
accept
unbalanced
input
via
standard
1/4”
SPEAKER
terminal
is connected
to
the
"—"'
speaker
input
phone
plugs.
The
BALANCED/UNBALANCED
switch
terminal.
|
should
be
set
to
UNBALANCED
when
using
these
inputs.
These jacks can also be used as send terminals.
Ө PIN 1GND SW
Couples or decouples the canon connector earth line (pin 1, о BALANCED/UNBALANCED Switch
shield). Normally ON. In some cases where ground loops Determines which input connectors are active. In the
cause
excessive
hum,
turning
the
ground
switch
OFF
can
BALANCED
position,
input
signals
are
accepted
via
the
interrupt the loop and reduce the hum. balanced Canon connectors, and in the UNBALANCED
position input is accepted via the unbalanced phone jacks.
Ө Canon Connectors (XLR-3-31)
These connectors are generally used as inputs. Pin 1 is @ MODE Selector Switch
shield,
pin
2
is
hot
and
рт
3
cold.
Compatible
connectors
Determines
whether
the
amplifier
is
to
operate
in
the
stereo
include
Canon
XLR-3-12C
and
Switchcraft
5C-1055A.
or
mono
(BTL)
mode.
©) Canon Connectors (XRL-3-32)
Compatible with Canon’ XLR-3-11C ог switchcraft
5C-1056A connectors, these connectors are useful for send-
ing the input signal to other power amplifiers.

+ |
—
ыюъмы
‚АА
=
:
GENERAL
SPECIFICATIONS
о
а
с
POWER OUTPUT LEVEL
Continuous
average
sine
wave
power
with
less
than
0.05% THD. 20 Hz to 20 kHz.
Stereo,
8ohms.........
ip
UIS
240W
+
240W
Mone,
16
оћтѕ
....................
480W
Mono,8ohms
......................
700W
FREQUENCY
RESPONSE
10
Hz
to
50
kHz,
8ohms,
1М/............
2058
POWER BAND WIDTH
Stereo 8 ohms 120W
THD
ОМ
Фа
а
а
ылыы
10
Hz
to
100
kHz
Mono
16
ohms
240W
THD
0.1%
.....
ани
10
Hz
to
100
kHz
TOTAL HARMONIC DISTORTION
Stereo 8 ohms 120W
TkHz...................
Less
than
0.003%
Mono
16
ohms
240W
|
20
їо
20
КН2
..............
Less
than
0.007%
Mono
8
ohms
350W
201020КН2...............
Less
than
0.01%
INTER MODULATION DISTORTION
70 Hz 7kHz mixed 4: 1
Stereo
8
ohms,
120W
.........
Less
than
0.01%
Mono
16
ohms,
240W
.........
Less
than
0.01%
INPUT SENSITIVITY
Input
level
which
produces
100W
output
into
8
ohms
tate
Seg
E
A
EEES
0
dB
(0.775
V
rms)
INPUT IMPEDANCE
Balanced
and
unbalanced
inputs,
maximum
attenuator
setting
..............
TD
25
kohms
8
OHM
DAMPING
FACTOR
КА
и
vas
vei.
Greater
than
350
201020КН2...............
Greater
than
200
S/N
RATIO
Input
shorted
at
@12.47
kHz
............
110
dB
Input
shorted
at
@IHFA
...............
115
dB
SLEW
RATE
Stereo8ohms
...................
60
V/usec
Mono
1боһтз...................
90
V/usec
CHANNEL
SEPARATION
8
ohms
120W
ТКН
pM
Mn
TL
95
dB
8
ohms
120W
201020КН2,............
MORE
80
dB
RELAY
MUTING
TIME
42
From
power
on
...................
have
4
14
sec
INDICATORS
РОМЕ
ON
и
Cosy
Дыл
АКУ
шга
кылы
LED
Protection
(Relay
OFF)
..................
LED
Thermal
Overload
(85
+
5
degrees
C)
.........
LED
Clipping
(2%
THD)
................
шил
ТЕР
Peak Power Meters (PC2002M only)
. .
.
—50
dB
to
+50
dB
range
O
dB
=
100W
into
8
ohms
FRONT PANEL CONTROLS
Power
буйсн...............
Push-ON/Push-OFF
Input Attenuators (one per channel)
гэгээ
22
detent
positions
in
—1
dB
steps
(0, —1,—2...-—20, ®)
REAR
PANEL
CONTROLS/CONNECTORS
Mode
switch
.................
STEREO/MONO
Pin
1
GND
Switch
(XLR
connectors)
,.....
ON/OFF
Balance/Unbalance
Switch
.....
BALANCED
(XLR)/
UNBALANCED (PHONE)
POWER REQUIREMENTS
U.S.
&
CANADIAN
models
...
....
AC120V,
60
Hz
GENERAL
Model.........
АС220/240\,
50/60
Hz
POWER
CONSUMPTION
|
U.S.
8
CANADIAN
models
..............
700
W
GENERAL
тоде!..........
РОА
1600
W
DIMENSIONS
(үх
рхнН)...............
480
х
413
х
183
тт
(18-7/8" х 16-1/4" x 7-1/4”)
WEIGHT
PC2002
араа
аа
каа
Ми
20
kg
(44
pounds)
РС2002М
.................
20.5
kg
(45
pounds)
NOTE:U.S.
8:
CANADIAN
Models
must
be
operated
into
8
ohms
in
stereo
mode
and
16
ohms
in
mono
mode
in
accordance
with
safety
regulations.
All
specifications
subject
to
change
without
notice.

PERFORMANCE GRAPHS
[27] пина и
1000 : оов
$ Я бог
Be H оо! ===
. 0005 =I a - Г
Fig. 3 зоо нЕ Fig. 7
Io! ооо!
5 ^ 5 LOAD IMPEDANCE Bor mnm о: 02 os а 2 оџтрот POWER” so юо 200 юм
LOAD IMPEDANCE VS OUTPUT POWER T.H. DISTORTION
THD 0,05% Mode STEREO Load Impedance 82
Single Channel Driven Mode STEREO
Both Channel Driven
IN/OUT Channel A
4-3-4---4-1---- Ш [^]
м
1000 шини шш ишш шша = ог
m
3
ЫГ
Ф
ол
|
300
|
оов
==
gro @ |
Бо ЕЕН T ЕН Зоог
20
|
Fig.
4
9005
ю 100 шэнжэ ЮК (He) ооо "nM Fig. 8
POWER BAND WIDTH 9001 са ог ољ t 2 5 10 20 Бо 00 200 500 (4)
Load Impedance 162 а а 80 OUTPUT POWER
Mode
MONO
Mode
STEREO
Load
Impedance
162
т Both Channel Driven Mode MONO
s E |
| Г о кај
ш 100 аша
i- Ф ЦЭ
йл ШИ i i
ni 5 mi BAL IN
-5 HH 3 20 x
>
Г]
i
lo
H
|__|
Е
IN
M
:
Г
ЕЕ:
79 Fig. 5 3 +H
юго 50 00 200 бо Ik әк Sk пок 20 50к (HD 8 2 4-4 Fig. 9
FREQUENCY .
FREQUENCY.RESPONSE ' 105 Nm ТОК UR
(D Load Impedance 162 @ Load Impedance 80 INPUT IMPEDANCE
Power Output Power Output Mode STEREO
= 1W at 1kHz = 1W at 1kHz
Mode MONO Mode STEREO
Channel A Channel A & B
(UNBAL INPUT) (UNBAL INPUT) |
|
“) НИ
1000 H 05 | Н
500 |-| ЕНН 3 и ry
8 о 71717 5 04 i
2
(00
ae
Bos
FE
Е
[У | г
S
вю
{=
17
0.05
й 0.02
зо ' Fig. 10
И
|||
Fig.
6
оо
100
FneluENCY
пок
(на)
9 100 re ute ток (HR) 1 OUTPUT IMPEDANCE
DAMPING FACTOR | Load Impedance 82
Load Impedance 82 ) | Mode STEREO
Моде STEREO

The following are actual oscilloscope photographs made by an in-
dependent testing laboratory.
НЕЕ ~
20 Hz Square-Wave Response
Remarkably accurate response at this low frequency ensures
that bass reproduction will be tight and clean.
рүү
ИШИШ ЕШШ ·: :
1 kHz Square-Wave Response
Flawless midrange response is immediately evident in this
scope trace. There is no unnatural response rolloff, ringing or
overshoot to interfere with music reproduction.
Ши сн
cutn
pea | |
ГГ =:
20 kHz Square-Wave Response
Although 20,000 Hz is well beyond the range of human hear-
ing, the response accuracy shown here means that upper-
range harmonics vital to natural reproduction will be proper-
ly reproduced,
|| |||
шатлан
Шин ажи
А
Мур А
И
| | 7 БШ БИШ
ШИ -.
Total Harmonic Distortion with a 1 kHz Sine Wave Signal:
The distortion components shown in this trace are actually a
mere 0.001496, It's this type of low-distortion performance
that makes the PC2002 and PC2002M ideal for demanding
professional applications.
VEN
BIO
Mus. imd.
ши
ENNENNENN =>
Total Harmonic Distortion with a 20 kHz Sine Wave Signal
Although the amp is delivering 240 watts (mono, BTL)
output power continuously at 20,000 Hz, harmonic distor-
tion is no more than 0.0036%. That means clean, transparent
highs, even on high-level peaks,
Kf
МУТ |
АУ
Шимт дани
Шинэ шин
РИА
МЕТ
о -<
Slew Rate and Rise Time 1
Stereo mode, 8 ohm load f=2 kHz : GOV/uS slew rate
шаншаннн
Шина
А
| У |.
шинэ шин
АРА
УК Мм |
с --
Mono mode, 16 ohm load, f=2 kHz: 90V/uS slew rate.
BEN Шин
HERE
ШШЕ Е ШШШ
1 -
Stereo mode, 8 ohm load, f=1 kHz: 1.848 rise time.
Here's your guarantee of exceptional transient response. Extremely
high slew rate and fast rise time mean precise signal
reproduction.
[1uS/horizontal division, 20 V/vertical division]

А DISCUSSION OF SPECIFICATIONS
POWER OUTPUT
Types of Power Ratings
Peak power refers to the maximum undistorted power
output of an amplifier. Most amplifiers cannot sustain their
peak power ratings for long periods of time without
external cooling fans. Because there are many different
methods of rating an amplifier's peak power, it is hard to
objectively compare the peak power ratings of two
amplifiers. The peak power rating is primarily useful for
determining an amplifier’s ability to reproduce the peaks
and transients in a musical program, peaks which may be
20dB or more above the average power level. The ability to
accurately reproduce these high power peaks in a musical
program is one of the most important advantages of the
PC2002M as compared to a smaller power amplifier.
“RMS” power is actually a misnomer for average power.
Average power is usually measured with a sine wave input
signal, and is equal to the amplifier’s RMS output voltage
squared and then divided by the load impedance. Because
RMS voltage is used in the formula, the resulting power
rating is commonly called “RMS power”. While it means
.the same as "RMS power", to be more accurate, the
PC2002M is rated in watts of "continuous average sine
wave power”,
Since the PC2002M is a professional power amplifier, not
sold for home hi-fi use, it is not required to meet the power
rating standard set by the FTC (Federal Trade Commis-
sion), a standard meant for consumer power amplifiers.
However, the PC2002M is measured under severe condi-
tions which simulate the most demanding professional
usage. Thus, the PC2002M would easily meet the FTC
ratings for consumer amplifiers. In addition, the PC2002M
user has the benefits of professional features and reliability.
Reasons for a High Power Amplifier
An interesting characteristic of the human ear is described
by the "Webe-Fechner" law. In its general form, the law
applies to al! our senses:
The amount of additional stimulus needed to produce a
perceptible change is dependent on the amount of stimulus
already present.
In mathematical terms, the Weber-Fechner law suggests that
the human ear responds to changes in sound level in a
logarithmic manner. More simply this means that for a
sound to seem twice as loud, it requires approximately ten
times as much acoustic power (and therefore ten times as
much amplifier power). Thus, the PC2002M's high power
output capabilities are extremely valuable.
One of the other benefits of high power output is the
ability of the amplifier to easily reproduce high peak power
transients (which may be 100 times the average program
power, or even more).
DISTORTION (Refer to Figures 7 and 8.) |
The PC2002M is designed to have the lowest possible dis-
tortion. There are many different forms of distortion,
however, and comprehensive distortion ratings offer a
means to compare the performance of different amplifiers.
Harmonic Distortion, is characterized by the appearance.at
the amplifier output of harmonics of the input waveform
which were not present in the original input waveform;
Total Harmonic Distortion, or T.H.D. is the sum total of all
of. these unwanted harmonics expressed as a percentage of
the total signal.
Harmonic distortion, in an amplifier, can be created in any
of several ways. The Т.Н.О. rating of a power amplifier
refers to creation of unwanted harmonics by the amplifier
during “linear” operation (normal input and output levels,
impedances, etc.). Harmonic distortion is also created by
"clipping", a form of "non-linear" operation, which occurs
when the signal level at an amplifier's input is high enough
to drive the amplifier beyond its rated maximum output.
The amplifier, in attempting to reproduce this signal,
reaches its maximum output voltage swing before it
reproduces the top of the signal waveforms. Since the
output voltage cannot rise any farther, the tops of the
waveform are "squared off’, or clipped. Clipping distortion
adds odd upper harmonics (3rd harmonic, 5th, etc.) to the
original signal. (Input clipping would be similar, where the
input stage of the amplifier is overdriven by a high level
input signal.) The PC2002M has wide input headroom and
extremely high peak power output capabilities (headroom)
to help avoid the problems of clipping distortion.
Another form of harmonic distortion that occurs in some
power amplifiers is called crossover distortion. * Crossover
distortion can be caused by improper bias in the output
transistors of an amplifier. The amount of crossover distor-
tion stays the same whether the signal is large or small, so
the percentage of distortion goes down as the signal level
goes up. Thus, an amplifier with crossover distortion may
sound relatively distortion free at high output levels, yet
sound “fuzzy” at low levels. Some amplifiers have internal
adjustments which enable a service technician to control
the amount of output transistor bias, and therefore control
the distortion.
Fig. 19A — Large Amplitude Sine Wave with Crossover
(notch) Distortion. :
D CE N
Fig. 19B — Smailer Amplitude Sine Wave with same amount
(higher 96) of Crossover (notch) Distortion.
*"Crossover", in this case, refers to the transition between the
positive half and the negative half of the output voltage waveform in
a "push-pull" class B or AB power amplifier: it has nothing to do
with the crossover used to divide frequencies in a speaker system.
See Figure 19.

Intermodulation Distortion, or I.M. is characterized by the
appearance in the output waveform of frequencies that are
equal to sums and differences of integral multiples of two
or more of the frequencies present in the input signal. The
difference between intermodulation distortion апа
harmonic distortion is that two or more different fre-
quencies must be present to produce intermodulation
distortion (only one frequency is needed for. harmonic
distortion to appear), and that intermodulation distortion
products may not be harmonically related to the original
frequencies. Like its harmonic distortion figure, the inter-
modulation distortion in the PC2002M is low enough to be
virtually inaudible even in the most critical situations.
FREQUENCY RESPONSE (Refer to Figure 5)
The frequency response of the PC2002M describes the
variation in its output signal level with frequency when the
input signal is held constant. The extremely "'flat" frequen-
cy response curve of the PC2002M is an indication of its
overall quality and its ability to respond to upper and lower
harmonics of signals all the way to the extremes of the
. audio spectrum.
Because extreme stability is necessary for some types of
commercial sound applications, some manufacturers restrict
frequency response or allow relatively high distortion in
return for increased amplifier stability. The PC2002M, on
the other hand, has excellent frequency response and ultra-
low distortion, yet is inherently stable under the most
difficult loads, even in the "mono" mode.
The frequency response of the PC2002M has been inten-
tionally limited, however, at very low frequencies (sub-
audio). Because of this, severe low frequency transients, or
DC offset, appearing at the input to the PC2002M are
unlikely to damage a speaker load. Other amplifiers which
are DC coupled throughout may have a "'flatter'' sub-audio
frequency response, but this makes them capable of ampli-
fying dangerous DC input voltage or sub-audio transients
and delivering them (at high power) to a speaker.
POWER BANDWIDTH (Refer to Figure 4)
The power bandwidth of the PC2002M is a measure of its
ability to produce high power output over a wide frequency
range. The limits of the power bandwidth are those points
where the PC2002M can only produce 1/2 the power that it
can produce at 1000Hz. While the frequency response is
measured at relatively low power output (1 watt), the
power bandwidth is measured at the PC2002M's full power
output (before clipping). The power bandwidth of the
PC2002M is quite “Нат”, and extends to 100kHz, well
beyond the limits of the audio spectrum.
The wide power bandwidth of the PC2002M means that it
can reproduce high level upper harmonics of a signal as
easily as it can reproduce mid-range fundamentals. It means
that you get full power performance from the PC2002M
over the entire audio frequency spectrum. This is especially
important when the amplifier is called upon to reproduce
musical material with high energy over a wide frequency
range, such as rock and roll.
CHANNEL SEPARATION
This specification indicates the output from one channel
when a signal is fed to the other channel. The PC2002M's
channel separation is very good, which means that even
critical stereo programs will be unaffected by crosstalk
between channels.
HUM AND NOISE
Hum or noise from a power amplifier disrupts a program,
and is irritating to a listener. Hum and noise. could be
considered a form of distortion. The PC2002M's hum and
noise are so low that they are completely inaudible under
any normal listening circumstances.
SLEW RATE А
Slew rate is a measure of а power amplifier’s ability to
follow: a fast rising waveform at higher frequencies and
higher power outputs than the rise time measurement.
It might seem reasonable to assume that the fastest slew
rate for an audio waveform occurs at 20kHz. However, this
is not the case. When one frequency is superimposed upon
another, the combined waveform has a slew rate that is
greater than the slew rate of either signal by itself. The
actual value of the slew rate of one of these waveforms (or
any waveform) depends not only on the frequency, but on
the amplitude of the waveform as well. Thus, the criteria
for a good slew rate specification, which indicates that an
amplifier can reproduce these combination waveforms,
varies with the maximum power output capability of the
amplifier. The higher the power, the higher the required
slew rate. With a 60 volts/microsecond slew rate, the
PC2002M can easily reproduce even the most extreme
audio waveforms at its full power output.
INPUT IMPEDANCE
The input impedance of the PC2002M is high enough to
allow it to be used with most semi-pro devices, or to be
used as a “bridging” load for а 600-ohm source.
INPUT SENSITIVITY
The PC2002M's input sensitivity indicates the input drive
voltage needed for the PC2002M to produce its rated
output of 240 watts into 8 ohms (input attenuators are
adjusted to maximum clockwise rotation for minimum
attenuation).
PROTECTION CIRCUITS AND
THERMAL SPECIFICATIONS
The PC2002M is one of the safest amplifiers you can find.
It incorporates multiple protection circuits—transient
suppression, current limiting, short circuit and overload
protection, dc offset sensing with relay disconnect, powered
transformer overtemperature sensing with auto shutdown—
to prevent speaker damage in the event of an amplifier
failure, and to prevent amplifier damage in the event of a
load or cable problem. Because the circuits function auto-
matically, front panel LEDs are installed to inform the
operator of overload protection status. A thermal LED
also warns of excessive heat sink temperature.
GAIN
Gain is the ratio of the PC2002M's output voltage to its
input voltage.. Maximum gain occurs when the input
attenuators are set for minimum attenuation. If the input
and output voltage are specified in dB, the voltage gain is
equal to the difference of the two dB numbers. As stated
under : INPUT SENSITIVITY, an. input voltage of OdB
(0.775 volts) produces an output power of 100 watts into
an 8-ohm load.