Yamaha P-2200, P-2201 User Manual
YAMAHA
AUTHORIZED
PRODUCT MANUAL
P-2200/2201
SYSTEM AMPLIFIER
P-2200/2201
OPERATING MANUAL
ABOUT THIS MANUAL
SCOPE
The P-2200 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 P-2200's performance depends on system
design and installation, in addition to its own capabilities.
Thus, the P-2200 Operating Manual is system oriented,
describing system design parameters and installation
techniques, as well as the operation and performance of
the P-2200.
Additionally, this manual reviews a few of the basic
mathematic tools used in system design, from dB to
Ohm's law.
ORGANIZATION
We recommend that you read the entire Operating
Manual. However, if you are using the P-2200 in an
existing system, and you are familiar with high power
amplifiers, the BRIEF OPERATING INSTRUCTIONS,
Pages
One 1 &
basic connections and operation.
The SPECIFICATION sections, (Sections THREE
and FOUR) are highly detailed, including oscilloscope
photos, and discussions of the P-2200's excellent
performance specifications. The last part of the
SPECIFICATIONS section is a discussion of the
advantages of professional equipment, like the P-2200,
compared to hi-fi or semi-pro equipment.
The INSTALLATION AND DETAILED
OPERATION section, which begins on Page SIX 1,
includes more complete instructions, special considerations for using the P-2200 "on the road," as well as in
permanent commercial and studio installations. This
section also covers grounding and shielding concepts,
cabling considerations, and several other topics.
The APPLICATIONS section, which begins on Page
SEVEN 1, discusses the use of the P-2200 in several
typical setups, and includes wiring diagrams. This section
also covers other devices that are normally associated
with a power amplifier, from graphic equalizers to
compressor/limiters.
The APPENDIX, on Page EIGHT 1, discusses
definitions of a number of the terms used in the manual,
and reviews some of the basic mathematic tools used in
system design, such as the dB, Ohm's law, voltage
division, and power formulas.
2,
contain all the
information
necessary
for
NOTE: The P2201 is identical to the P-2200 except
there are no Peak Reading Meters.
THE P-2200/2201 BRIEF OPERATING INSTRUCTIONS SECTION ONE
INTRODUCTION SECTION TWO
GENERAL SPECIFICATIONS SECTION THREE
PERFORMANCE GRAPHS & A DISCUSSION OF SPECIFICATIONS SECTION FOUR
THE DISTINCTION BETWEEN PROFESSIONAL AND HI-FI EQUIPMENT SECTION FIVE
IMPEDANCE
OPERATING LEVELS
DYNAMIC RANGE
GAIN OVERLAP AND HEADROOM
INPUT SENSITIVITY RATINGS
PROFESSIONAL EQUIPMENT ADVANTAGES
INSTALLATION AND DETAILED OPERATION
SECTION SIX
PHYSICAL MOUNTING
CABLING AND IMPEDANCE MATCHING
ACTIONS OF THE P-2200 PROTECTION CIRCUITS
GROUNDING AND SHIELDING
AC: POWER, FUSES, ACCESSORY OUTLETS, WIRING, SAFETY
MONO OPERATION
APPLICATIONS
SECTION SEVEN
13
13
16
17
BIAMPLIFICATION AND TRIAMPLIFICATION
ECHO, REVERB AND DELAY
COMPRESSION AND LIMITING
EQUALIZATION, HIGH AND LOW PASS FILTERS
SPEAKER PROTECTION
SPECIFIC APPLICATIONS
APPENDIX
SECTION EIGHT
DEFINITION OF TERMS: dB, dBV, dBm and dB SPL
SPECIAL USE OF dB (VOLTS) IN THIS MANUAL
OHM'S LAW
POWER
IMPEDANCE
SERIES AND PARALLEL IMPEDANCE CONNECTIONS
VOLTAGE AND CURRENT DIVISION
BALANCED, UNBALANCED, AND FLOATING CIRCUITS
TRANSFORMERS
1
2
2
4
4
4
1
2
1
3
3
4
6
7
1
1
2
2
3
3
4
5
5
THE P-2200/2201 BRIEF OPERATING INSTRUCTIONS
Fig. 1A - P-2200 Front Panel
Fig. 1B - P2201 Front Panel
A. Input Attenuators
Calibrated, stepped input attenuators lower input
signal levels ahead of amplification stages.
B. Peak Reading Meters (P-2200 only)
Meters display instantaneous (peak) power output
into
an
8-ohm load
over a full
50dB range;
"0dB"
=
100 Watts into 8 ohms.
C. Thermal Warning Indicator
Warns of overheating before thermal protection
circuit turns off the AC power.
D. Power Indicator
Glows when the power switch is "on."
E. On-Off Switch
Controls AC power to the P-2200 or P2201.
NOTE: The P2201 is identical to the P-2200 except
there are no Peak Reading Meters. Both are made to be
mounted in a standard 19" wide electronic equipment
rack. Each of them takes up 7" (17.6cm) of vertical
space, and extends 13" (33.0cm ) behind its front panel.
For portable racks, we recommend bracing the rear of
the amplifiers.
Fig. 2A - P-2200 Rear Panel*
Fig. 2B - P2201 Rear Panel*
A. Input Connectors
The two XLR input connectors on each channel are
unbalanced and are wired in parallel with each other
and with the two phone jacks (tip/sleeve type).
B. Input Polarity Switch
Determines the polarity of the two XLR input
connectors (Pin 2 or Pin 3 "
hot
");
does
not
affect
the
two phone jacks. See diagram on the rear panel.
NOTES:
1. Input impedance is 25k-ohms minimum; +4dB
(1.23V) produces 230 watts output into 8 ohms
(44.7V).
2. Input channels may be parallelled by connecting
them together with phone to phone or XLR to XLR
cables as shown on Page SIX 7.
3. Input transformers for matching or isolation,
should be located several inches from the P-2200 or
P2201's power transformer
C. Output Connectors
Standard 5-way binding posts (3/4" spacing) accept
banana plugs or direct-wired connections.
NOTES:
1. Maximum power output into 8 ohms is 230 watts;
power output rises at lower impedances.
2. Protection circuitry towers power output when
load impedance falls below 2.5 ohms.
for
maximum
hum
rejection.
D. AC Power Cord
For the U.S. and Canadian models, the P-2200/2201
require 117 VAC 50 or 60 Hz line (105 V min., 135 V
max.; 8 amps max. at 120 volts).
For the Australian model: 240V AC 50 or 60 Hz.
For other territories' models, an internal voltage
selector (220 V/240 V switchable) is provided near the
rear panel. In this case 220 V is factory-preset. If you
want
to
change
into
240 V line,
consult
your
nearest
Yamaha dealer.
E. Fuses
7 amp, 125 volt (x 2), type AGC (3AG); U.S. and
Canadian models only. 4 amp, 250 volt (x 2); other
territories models. Fuses should always be replaced
with
same
size
and
type.
If
the
fuses
blow
consistently,
the amplifier should be checked by a qualified Yamaha
service technician.
F. AC Accessory Outlets
These convenience outlets are made for low power
cooling fans. Not provided in certain areas.
The rear panels shown here are subject to U.S. specifications.
INTRODUCTION
The P-2200 is not just "another big amplifier;" it is
an exciting new approach to high power sound. Yamaha's
leadership is clearly demonstrated by the P-2200's professional features, sophisticated design, and uncompromising performance.
PEAK READING METERS*
Instead of the more common and slow responding
VU meters, the P-2200 has PEAK READING METERS
that
accurately display a full
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 overdriving the system, thereby preventing the "clipped"
waveforms so dangerous to drivers and loudspeakers.
CALIBRATED INPUT ATTENUATORS
The P-2200 has log-linear INPUT ATTENUATORS to
complement its peak reading meters. The input attenuators are marked in 22dB-calibrated steps, detented for
extra accuracy. The attenuators provide a smooth, noise
free transition from the highest to the lowest audio level.
dB-calibrated
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 tracking.
INPUT AND OUTPUT CONNECTIONS
INPUT CONNECTORS for each channel include one
"male" and one "female" XLR connector (unbalanced)
plus two parallel phone jacks. This provides the flexi-
bility
necessary
amplifier, as well as for adapter-free connection to
almost any mixer. A POLARITY switch allows either
pin 2 or pin 3 of the XLR to be chosen as the "hot"
lead, satisfying DIN/JIS or USA standards. Outputs are
standard five way binding posts, usable with high current
"banana" plugs or direct wired connections.
MONAURAL OPERATION
The P-2200 may be converted to a monaural "super
amplifier" by inserting two matched transformers
ahead of the inputs, feeding the same signal to both,
and reversing the POLARITY switch on one input. This
creates a transformerless balanced output, the speaker
load "bridged" across the "hot" terminals of both
channels. In this mode, the P-2200 is suitable for
driving almost any load, including highly reactive 70-volt
commercial speaker lines. With a full 400 watts into
16 ohms, the P-2200 in mono mode eliminates the need
for several smaller 70-volt amplifiers.
input
attenuators
for
convenient bridging
five
have
decades
numerous
to
(50dB)
another
of
PERFORMANCE
The P-2200's performance is as impressive as its
features. At a sustained output of 230 watts into 8 ohms
(for each channel), there is plenty of punch to reproduce
the powerful peaks essential to clean studio monitoring.
High power handling also makes the P-2200 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 P-2200
0.05% THD at full rated power - the kind of low
distortion that is undetectable by even the most critical
listeners.
A high damping factor of better than 300 at
frequencies below 1kHz reduces the tendency for
speaker cone overshoot, giving tighter and better defined
bass response. On the other end, the P-2200's frequency
response extends well beyond 100kHz, 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 P-2200
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 P-2200 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 P-2200 weighs a modest 44 pounds
(20kg)** 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 P-2200
should
service
ever
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 P2201 does not have the Peak Reading Meters.
* * The P2201 weighs 42 pounds (19kg)
has
be
required, the
ultra-low
is
extremely reliable.
distortion,
unit
is
designed
less
Still,
for
than
GENERAL SPECIFICATIONS
Power Output Per Channel: (Refer to Figure 3. Ambient
room temperature for tests: 25-degrees Centigrade.)
200 Watts continuous average sine wave power into
8
ohms
with
less
than
0.05%
THD,
(Total
Harmonic
Distortion), over a bandwidth of 20Hz to 20kHz,
both channels driven.
230 Watts continuous average sine wave power into
8
ohms
with
less
than
0.05%
THD,
channels driven.
at 1 kHz,
Frequency Response: (Refer to Figure 5.)
+0dB, -0.5dB, 20Hz to 50kHz.
Total Harmonic Distortion: (Refer to Figure 6.)
Less than 0.005% @ 50 Watts, 8 ohms, 1kHz.
Less than 0.01% @ 150 Watts, 8 ohms, 20Hz to
20kHz.
Intermodulation Distortion: (Refer to Figure 7.)
Less than 0.01% using frequencies of 70Hz and
7kHz, mixed in a ratio of 4:1, single channel power
output of 150 Watts into 8 ohms.
Input Sensitivity:
An input of +4dB* (1.23V), ±0.5dB, produces an
output of 230 Watts into 8 ohms (maximum output
power), INPUT attenuator set for maximum level.
Input Impedance:
25k-ohms, minimum (unbalanced).
Damping Factor: (@ 8 ohms / (Refer to Figure 8.)
Greater than 300 at any frequency from 20Hz to
1kHz; greater than 70 at any frequency from 20Hz
to 20kHz.
Actual Output Impedance: (Refer to Figure 9.)
Less than 0.04 ohms, from 20Hz to 10kHz.
Hum and Noise:
At least 110dB signal-to-noise ratio (l.H.F./A.S.A.
No. Z24.3-1944).
Rise Time:
3.8 microseconds, or better (10%-90% of 1 volt @
1kHz square wave output).
Slew Rate:
45 volts per microsecond, or better (at 175 Watts into
8 ohms, 200kHz square-wave input).
Channel Separation: (Refer to Figure 10.)
At least 82dB at 1kHz, at least 75dB at 20kHz.
*In these specifications, when dB represents a specific voltage,
0dB is referenced to 0.775V. "dB" is a voltage level, whereas
"dBm" is a power level. 0dBm is referenced to 1mW (0.775V
driving a 600-ohm termination). For example, when 12.3V is
fed to a high impedance, the level is designated "+24dB." When
+24dB (12.3 volts) drives a 600-ohm termination, the level is
designated "+24dBm." The level in "dB" is specified, wherever
applicable, to avoid confusion when the input is fed by various
low and high impedance sources. See the APPENDIX beginning
on Page EIGHT 1 for a further discussion of dB.
both
Phase Shift: (Refer to Figure 11.)
20Hz to 20kHz, ±10 degrees.
Offset Voltage:
Less than ±10mV DC.
Unit Step Function Response: (Refer to Figure 27.)
See scope photo (Page FOUR 4) and discussion,
Page FOUR 6.
Thermal Specifications:
Massive black anodized heat sinks are thermally
joined with the chassis, thereby utilizing the entire
amplifier as a heat sink.
Protection Circuits:
Thermal warning light turns on when heat sink
temperature reaches 100-degrees Centigrade.
A self-resetting thermal switch shuts down the AC
power if the power transformer winding temperature
reaches 130-degrees Centigrade. See Page SIX 13 for
power overload circuit specs.
Turn On/Turn Off Specs:
There is no turn off transient; the turn on transient
is
minimal
(see
Page
SIX
13).
Warm
up
time
is
less
than 0.2 seconds.
Power Requirements:
For the U.S. and Canadian models: AC, 120 Volts
nominal, 50-60Hz (105V min., 135V max.); 8
amperes maximum at 120V AC; 960 volt-amperes
maximum at 120 Volts; approximately 57 voltamperes at idle.
For other territories models: 1,300 Watts, 220 or 240
Volts AC nominal, 50-60Hz.
Efficiency: (Refer to Figure 12.)
As high as 63%; see Page FOUR 2.
NOTE: All performance specifications are made on U.S.
and Canadian models at an AC line voltage of 120 Volts
±1%, using a ±1% nonreactive load resistor at an
ambient room temperature of 25-degrees Centigrade.
Also effective for other territories' models.
Input Connectors:
One "male" and one "female" XLR connector in
parallel,
(shield); switchable
pin 2 "hot,"
pin 3 connected
for
pin 3 "hot."
to
pin
1
XLR's are unbalanced and in parallel with two tip-sleeve
(standard) phone jacks.
Output Connectors:
Standard 3/4-inch spacing, "5-way" binding posts.
Meters and Indicators:
Two peak reading meters (one per channel) indicate
the instantaneous power output, over a 5-decade
(50dB) range. "0dB" represents 100 Watts into
8 ohms. (P-2200 only)
One "power ON" indicator LED; one "Thermal
Overload" indicator LED.
Meter Rise Time (P-2200 only):
Less
than
10
milliseconds;
(-40dB
to
0dB
on the scale).
Meter Release Time (P-2200 only):
Less
than
0.8
seconds; (0dB
to
-20dB
on
the
meter scale).
Meter Accuracy (P-2200 only):
See graph, Figure 13, Page FOUR 2.
Controls:
22-position, log-linear, detented, and dB-calibrated
INPUT ATTENUATORS (one per channel)
attenuate input signal in 2dB steps from 0dB
attenuation to -34dB, then steps of -37dB, -42dB,
-50dB, infinity; Power (ON-OFF) switch; INPUT
POLARITY switches.
Fuses:
AGC (3AG) type, 7-amps x 2 parallel fuses for the
AC line input (U.S. and Canadian models).
4-amps x 2 parallel fuses for the AC line input
(other territories' models).
Dimensions:
Mounts in a standard 19-inch (48cm) rack. 7" high
(17.6cm); maximum depth behind front panel is
13" (33.0cm); maximum depth including front
handles 14-1/2" (37.9cm).
Weight:
P-2200; 44 pounds (20kg), P2201; 42 pounds (19kg).
Color:
Semi-gloss black.
MONAURAL MODE SPECIFICATIONS
Power Output: (Refer to Figures 14 and 15.)
400
Watts
16
ohms
continuous
with
less
than
average
0.05%
sine
THD,
wave
20Hz
power
to
into
20kHz.
Frequency Response: (Refer to Figure 16)
+0dB, -1dB, 20Hz to 50kHz.
Total Harmonic Distortion: (Refer to Figures 17 and 18.)
Less
than
0.01% @ 300
Watts
into
16
ohms at 1kHz.
Intermodulation Distortion:
Less than 0.05% using frequencies of 70Hz and 7kHz,
mixed in a ratio of 4:1, at a power output of 200
Watts into 16 ohms.
Input Sensitivity:
An input of 0dB (0.775 Volts), ±0.5dB, produces an
output of 200 Watts into 16 ohms (INPUT attenuator
set for minimum attenuation, maximum level).
Input Impedance:
25K-ohms minimum (unbalanced).
Damping Factor: (@ 16 ohms) (Refer to Figures 19
and20).
Greater than 220 at any frequency from 20Hz to
1kHz; greater than 100 at any frequency from 20Hz
to 20kHz.
Hum and Noise:
At least 110dB signal-to-noise ratio (I.H.F./A.S.A.
No. Z24.3-1944).
Slew Rate:
35 volts per microsecond, or better, at 100 Watts into
16 ohms, 200kHz square wave input.
Specifications subject to change without notice.
PERFORMANCE GRAPHS &
A DISCUSSION OF SPECIFICATIONS
NOTE: In the discussion beginning on Page FOUR 5,
references to specific specifications assume normal stereo
operation (not mono operation) unless otherwise indicated.
Normal (Stereo) Graphs
Fig. 3 - Power Bandwidth vs Load Impedance Fig. 4 - Load Impedance vs Output Power
Fig. 5 - Frequency Response vs Load
Fig. 6A - T.H.D. vs Output Power at 8 Load Impedance
(both channels driven)
Fig.
6B - T.H.D.
(both channels driven)
vs
Output
Power at
16
Load Impedance
Fig. 7 - Intermodulation Distortion vs Power Output at
8 and 16 Load Impedance
Fig. 8 - Damping Factor vs Frequency at 8 Load
Impedance
Fig. 9 - Actual Output Impedance vs Frequency Fig. 10 - Crosstalk (Channel Separation)
Fig. 11 - Phase Response vs Frequency Fig. 12 - Power Consumption
Fig. 13 - Peak Program Meter Accuracy (P-2200 only)
Mono Mode Graphs
Fig. 14 - Power Bandwidth vs Frequency (Mono Mode)
at 16 Load Impedance
Fig. 16 - Frequency Response (Mono Mode) at 16 Load
Impedance
Fig. 15 - Load Impedance vs Output Power (Mono Mode)
at 0.1%
T.H.D.,
1kHz
Fig. 17 - T.H.D. vs Power Output (Mono Mode) at 16
Load Impedance
Fig. 18 - T.H.D. vs Frequency (Mono Mode) at 16 Load
Impedance
Fig. 20 - Actual Output Impedance (Mono Mode) vs
Frequency
Fig. 19 - Damping Factor vs Frequency (Mono Mode) at
16 Load Impedance
The following are actual oscilloscope photographs
made by an independent testing laboratory. The close
vertical
through
will
not
alignment
23
alter
Fig. 21 - 10Hz Square-Wave Response
The output waveform displays very respectable
low frequency
a
DC
speakers in the event any DC offset is fed to the
amplifier input.
depicts
musical
gain
of
of
input
very
wave
response.
unity,
and
output
low
phase
shift,
shapes.
The slight "tilt" shows
which
prevents
traces
so
damage
the
in
Fig.
amplifier
to
21
Fig. 24 - 1,000Hz Sine Wave, shown with HighlyMagnified Noise and Distortion Components
Even
at
full
P-2200's distortion is so low that it is almost
burried in the noise, which is at least 110dB
below the
clean and symmetrical.
230 watt
sine
wave
output
output.
(8-ohms), the
The
sine
wave
is
Fig. 22 - 1,000Hz Square-Wave Response
Near-perfect response is evident in the duplica-
tion
of the
input
form. There are no "squiggles" or spikes, meaning there Is no ringing or overshoot.
waveform
by
the
output
wave-
Fig.
25-20,000Hz
Magnified Noise and Distortion Components
While no amplifier should ever have to pro-
duce 230 watts continuous output at 20kHz,
P-2200
the
symmetrical reproduction. As In Fig. 11, the
noise (magnified here) is actually better than
110dB below the sine wave.
Fig. 26 - Square-Wave Response into a HighlyInductive Load (at 1kHz)
The ability of the P-2200 to maintain a
sharply defined square wave output into a
reactive load demonstrates stability under the
worst conditions. There is still a complete lack
of unwanted ringing, as well as low phase shift.
does it
Sine
with
Wave,
low
shown
distortion,
with
and
Highly-
Fig. 23 - 20,000Hz Square-Wave Response
The extremely fast and symmetrical rise and
fall times of the amplifier are evident, demonstrating the ability to accurately reproduce
musical waveforms and harmonics well beyond
the range of human hearing.
Fig. 27 - Unit-step Function Response
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 P-2200 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 (see Appendix). 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 P-2200 is rated in watts
of "continuous average sine wave power."
Since the P-2200 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
Commission), a standard meant for consumer power
amplifiers. However, the P-2200 is measured under
severe conditions which simulate the most demanding
professional usage. Thus, the P-2200 would easily meet
the FTC ratings for consumer amplifiers. In addition,
the P-2200 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 "Weber-Fechner" law. In its general
form, the law applies to all 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
P-2200'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). This subject is discussed
further
on
Pages
FIVE 2 and
Power Output versus Load
FIVE
4.
Within its maximum limits, the P-2200 acts like a
perfect voltage source (see Appendix), that is, its power
output
rises
with
decreasing
load impedance.
When
the
load impedance drops below 2.5 ohms, the P-2200's
protection circuits begin to limit the power, resulting
in the curve shown in Figure 4 (normal operation) and
Figure 15 (mono operation).
DISTORTION (Refer to Figures 6A-B, 7, 17, 18)
The P-2200 is designed to have the lowest possible
distortion. 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 T.H.D. 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, as that shown in Figure 65. 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 P-2200 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 distortion 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. The
P-2200 has automatic biasing circuitry which needs no
adjustment and avoids crossover distortion under all
operating conditions.
Fig. 28A - Large Amplitude Sine Wave with Crossover
(notch) Distortion.
Fig. 28B - Smaller Amplitude Sine Wave with same amount
(higher %) of Crossover (notch) Distortion.
"Crossover," in this case. refers to the transition between the
positive half and the negative half of the output voltage wave-
form 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 28.
Intermodulation Distortion, or I.M. is characterized
by the appearance in the output waveform of fre-
quencies 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 and harmonic distortion is that
two or more different frequencies 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 intermodulation dis-
tortion in the P-2200 is low enough to be virtually
inaudible even in the most critical situations.
Dynamic Frequency Response Shift is related to both
harmonic and intermodulation distortion. When high-level
low and high frequency signals are present in the same
waveform,
the
high
frequency
signals
"ride"
on
top
of
the
low frequency waveforms (see Figure 65, Page SEVEN 1).
If
amplifier
may
"push"
headroom
the
high
is
inadequate,
the
low frequencies
frequencies above the
output
limits
of the amplifier, clipping them off the waveform (Figure
65C). The low frequencies may remain unaltered, but the
high frequencies are severely reduced. At the same time,
harmonics of the high frequencies are produced which
add to the super high frequency content of the signal.
Thus, along with the distortion created by the clipping,
the frequency response of the original signal is drastically
altered. This type of distortion can be reduced by in-
creasing system headroom (using a more powerful
amplifier like the P-2200), and by biamplifying the
system as discussed on Page SEVEN 1.
The extremely low distortion figures of the P-2200
indicate its overall quality and mean that its sound will
be precise and natural.
FREQUENCY RESPONSE (Refer to Figures 5 & 16)
The frequency response of the P-2200 describes the
variation in its output signal level with frequency when
the
input
signal
is
held constant. The extremely "flat
"
frequency response curve of the P-2200 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, notably 70-volt lines
(see Page SEVEN 11), some manufacturers restrict frequency response or allow relatively high distortion in
return for increased amplifier stability. The P-2200, 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 P-2200 has been
intentionally limited, however, at very low frequencies
(sub-audio). Because of this, severe low frequency
transients, or DC offset, appearing at the input to the
P-2200 are unlikely to damage a speaker load. Other
amplifiers which are DC coupled throughout may have a
"flatter"
them capable of amplifying dangerous DC input voltage
or sub-audio transients and delivering them (at high
power) to a speaker.
OFFSET VOLTAGE
naturally present at the output of the amplifier. A high
DC voltage could damage the loudspeaker load; the
±10mV (10 one-thousandths of a volt) level from the
P-2200 is insignificant.
sub-audio frequency
response,
but
this
makes
This specification indicates the amount of DC voltage
UNIT STEP FUNCTION RESPONSE (Refer to Figure 27)
A unit step function is like the leading edge of a
square wave; it goes up, but never comes down. The
response to this input indicates the output of the P-2200
for a DC input signal which might come from a faulty
direct coupled preamplifier or mixer. Note that the
P-2200 will not reproduce a DC voltage fed to its input,
thus adding an extra measure of loudspeaker protection.
POWER BANDWIDTH (Refer to Figures 3 & 14)
The power bandwidth of the P-2200 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 P-2200 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
P-2200's full power output (before clipping). The power
bandwidth
of
the
P-2200
is
quite "flat," and extends
to
200kHz, well beyond the limits of the audio spectrum.
The wide power bandwidth of the P-2200 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
P-2200 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.
PHASE RESPONSE (Refer to Figure
11
)
The phase response of the P-2200 is a measure of the
amount of time delay it adds to different frequencies.
An amplifier with perfect phase response would introduce
equal time delay at all frequencies reproduced. The
P-2200's worst case phase shift of -10 degrees at 20kHz
corresponds to a 1.4 microsecond (1.4 millionths of a
second) delay period which is insignificant in even the
most critical audio applications.
Fig. 29 - Waveform of Amplifier with Poor Phase Response.
An amplifier with poor phase response would change
the shape of a waveform that was made up of a fundamental frequency and several harmonics by delaying
each harmonic differently. The effect might be similar
to that shown in Figure 29.
CHANNEL SEPARATION (Refer to Figure 10)
This specification indicates the output from one
channel when a signal is fed to the other channel. The
P-2200'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 P-2200's
hum and noise are so low that they are completely
inaudible under any normal listening circumstances.
RISE TIME
Rise time is a measurement of the amount of time an
amplifier requires to respond to a square wave at a
specified frequency. The rise time of an amplifier is an
indication of its frequency response. A fast rise time
corresponds to a wide frequency response. The P-2200's
rise
time
specification
is
measured
with a 1000Hz
square
wave output signal of one volt peak-to-peak amplitude.
The rise time is the time the amplifier requires to change
from 10% (0.1 volt) to 90% (0.9 volt) of its output. To
improve measurement accuracy, the first and last 10%
are normally not included in the test (any slight nonlinearities that occur in the test signal or the amplifier
could lead to measurement error).
SLEW RATE
Slew rate is a measure of a power amplifier's ability
to follow a fast rising waveform at higher frequencies
and higher power outputs than the rise time measurement. The P-2200's slew rate is measured with a 200kHz
square wave input signal, at 175 Watts output power
into 8 ohms.
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 45 volts/microsecond slew rate, the P-2200 can
easily reproduce even the most extreme audio wave-
forms at its full power output.
INPUT IMPEDANCE
The input impedance of the P-2200 is high enough
to allow it to be used with most semi-pro devices, or to
be
used
as a "bridging"
load
for a 600-ohm source.
Page SIX 2 details input impedance and level matching
for the P-2200.
INPUT SENSITIVITY
The P-2200's input sensitivity indicates the input
drive voltage needed for the P-2200 to produce its
rated output of 230 watts into 8 ohms (input attenua-
tors are adjusted to maximum clockwise rotation for
minimum attenuation).
PROTECTION CIRCUITS AND
THERMAL SPECIFICATIONS
See the discussions under INSTALLATION, on
Page SIX 13.
GAIN
Gain is the ratio of the P-2200'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 +4dB
(1.23 volts) produces an output power of 230 watts into
an 8-ohm load. 230 watts into 8 ohms implies an
output voltage of 43 volts which corresponds to +35dB
(referenced to 0.775 volts, as used in this manual). The
voltage gain of the P-2200, with its input attenuators set
for minimum attenuation, then, is 31dB [(+35dB)-(+4dB)].
OUTPUT IMPEDANCE (Refer to Figures 9 & 20)
The output impedance of the P-2200 is extremely
low. Thus, within its operating limits, the P-2200 is a
good approximation of a perfect voltage source and will
deliver increasing power levels into lower impedance
loads in a linear fashion according to Ohm's law. The
Appendix discusses Ohm's law and the concept of a
perfect voltage source.
DAMPING FACTOR
Damping factor is a term that is derived by
dividing the load impedance (speaker or other load) by
the amplifier's output impedance. Thus, a high damping
factor indicates a low output impedance at a specified
load.
The cone/voice-coil assembly of a loudspeaker gains
inertia during its back and forth movements. This
inertia can cause it to "overshoot," that is, to continue
movement in one direction, even when the amplifier
is trying to pull it back in the other direction. An
amplifier with a low output impedance can "damp"
(reduce) unwanted loudspeaker motions, as explained
below.
Fig. 30A - Speaker Cone at Rest
Fig. 30B - Speaker Cone moved outward by Postive-Going
Voltage from Amplifier.
Fig. 30C -
Speaker Cone has moved back PAST its rest position (overshoot)
and is producing a voltage of its own: "Back EMF"
Voltage from Amplifier has dropped to Zero but
During the "overshoot" movement, the voice coil of
the loudspeaker interacts with the loudspeaker's magnetic
assembly to produce a voltage called "back E.M.F."
(electro-motive force). This action is similar to the
operation of a dynamic microphone. If the amplifier's
output impedance is low, this "back E.M.F." voltage is
shunted through the amplifier's output circuits to
ground, and back to the voice coil. Since the path from
the voice coil, through the amplifier's output circuits,
and back to the voice coil is a complete circuit, a
current flows in the voice coil. This current, causes
the voice coil to act like an electro-magnet; the electromagnet (voice coil) interacts with the magnetic assembly
of the loudspeaker, and the unwanted overshoot is
reduced (a magnetic braking action).
Fig. 31 - Current produced by "Back EMF" follows path
through Amplifier's Output Impedance to speaker-coil.
If the amplifier's output impedance is low (considerably less than the impedance of the loudspeaker
voice coil), this damping action is limited only by the
resistance of the voice coil combined with the resistance
of the speaker lead wires. While the value of a high
damping factor in reducing cone overshoot is disputed,
the P-2200's high damping factor is evidence of good
overall engineering design.
THE DISTINCTION BETWEEN
PROFESSIONAL AND HI-FI
EQUIPMENT
In most applications, a variety of auxiliary equipment
will be connected to the P-2200, including: mixers, tape
machines, compressors, graphic equalizers, echo, time
delay, and reverb units, and just about any other audio
electronics imaginable. Regardless of the function of
auxiliary equipment, it will undoubtedly fall into one of
two general categories, professional type or hi-fi type.
The following criteria place most "semi-pro" equipment
in the hi-fi classification.
The distinction between professional and hi-fi equip-
ment is important primarily because it affects the way it
will be used with the P-2200. Brand name, size, panel
colors, durability and subtleties in function are not the
significant differences. What matters is that professional
equipment and hi-fi equipment usually operate at
different input and output levels, and require different
source and load impedances to function properly. The
P-2200 is designed to function well with other professional equipment, although it has high enough input
impedance and sensitivity to yield excellent results with
hi-fi type equipment if a few precautions are observed.
(These precautions are outlined in the Installation section of the manual.) The following paragraphs explain
how the specific requirements differ for professional and
hi-fi (or semi-pro) equipment.
IMPEDANCE
The inputs of a piece of professional audio equipment
are usually designed to be driven from a low impedance
source,
nominally
drive low impedance (600 ohm or higher) loads. (Power
amplifier outputs are not considered in this discussion.)
Professional input and output circuits may be
unbalanced, but they are often transformer isolated
(balanced or floating), and use dual conductor shielded
cables, with 3-pin XLR type connectors or Tip/Ring/
Sleeve phone plugs.
The P-2200's inputs are unbalanced due to cost and
adaptability factors. To internally balance the inputs of
the P-2200 would require two matched input transfor-
mers with heavy shielding (to avoid hum pickup from
the P-2200's power transformer). Induced hum in low
level circuits, especially in low level transformers, can
be a problem with any power amplifier, or other high
current device (such as a DC power supply). High quality
external
same
the user can choose the optimum impedance ratio for
a given situation, increasing the P-2200's adaptability.
Either the "matching transformer box" or "step up
transformer box" described on Pages SIX 3, and SIX 4
are suitable, so long as they are kept several inches
away from the P-2200.
to be driven from a 5,000-ohm (or lower impedance)
source, and its output will drive 10,000-ohm (or higher
impedance) loads. Hi-fi input and output circuits are
transformers
results
Hi-fi (and semi-pro) equipment generally is designed
150
to
600 ohms, and its
with
less
with a substantial cost
shielding can achieve
savings.
outputs
In
addition,
will
the
usually unbalanced, and use single conductor shielded
cables with 2-conductor connectors, either standard
phone plugs or phono plugs (also called RCA or pin
plugs). Occasionally, the inputs of a piece of hi-fi or
semi-pro equipment are professional XLR connectors
which have been converted to a 2-wire, unbalanced
circuit by internally connecting either pin 2 or pin 3
to
pin
1.
The nature of unbalanced, balanced, and floating
circuitry is discussed further in the Appendix of this
manual. For the purpose of this discussion, the most
significant point is that an unbalanced circuit is somewhat more susceptible to hum and noise, especially if
there is any irregularity in the grounding system.
NOTE: THERE IS NO CORRELATION BETWEEN
"BALANCED" OR "FLOATING" AND CIRCUIT
IMPEDANCE.
Low impedance and high impedance are relative
terms. A 150- to 250-ohm microphone is considered low
impedance, whereas a 10,000-ohm mic is considered
high impedance. A 600-ohm line is considered low
impedance, whereas 10,000-ohm, 50,000-ohm or
250,000-ohm lines are all considered high impedance.
Sometimes, mics and lines with an impedance of 600
ohms to about 2000 ohms are considered "medium"
impedance. NOTE: THE IMPEDANCE OF A CIRCUIT
SAYS NOTHING ABOUT ITS LEVEL.
While the exact transition between low and high
impedance is not clearly defined, the distinction is still
important, primarily because the output impedance of a
source determines the length of cable that can be
connected between it and a load before a serious loss
of high frequencies occurs. The losses occur because all
cables, and especially shielded cables, have some
capacitance between their conductors. Some guitar
coil cords may measure as high as 1000 picofarads total
capacitance! A source impedance (such as a high
impedance mixer output) and the capacitance of a
cable form a type of low-pass filter a filter that attenuates high frequencies. This filtering effect, can be
reduced by using low capacitance cable, by shortening
the length of the cable, by using a low impedance source
or by some combination of these methods.
Fig. 32 - The Source's Output Impedance and the Cable
Capacitance act as an "RC Lowpass" Filter which Attenuates
High Frequencies.
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