Yamaha 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.

Cables from high impedance sources (5000 ohms and
up), should not be any longer than 25', even if low
capacitance cable is used; shorten the cables if the
impedance is higher. For low impedance sources of 600
ohms or less, cable lengths to 100' are relatively effective.
For very low impedance sources of 50-ohms or less,

cable lengths of up to 1000 feet are possible with

minimal loss. However, the frequency response of the
source, the desired frequency response of the system,
and the amount of capacitance and resistance in the
cable all play a role in any potential high frequency
losses. Thus, these values are meant as guide lines, and
should not be considered fixed rules.

For short runs and in smaller systems with fewer
components, the performance of an unbalanced circuit
may be adequate. In a long cable run, a balanced or
floating circuit tends to reject hum and noise pickup
better than an unbalanced circuit, and in complex
systems, with several components separated by some
distance and running on different AC outlets, balanced
or floating circuits make proper grounding much easier.

In any given situation, the decision to use a hi-fi
(semi-pro) device or a professional one should be based
on the specifications of the inputs and outputs of that

device and on the requirements of the application.

OPERATING LEVELS

Nominal professional line level is usually +4dBm or
+8dBm; that is, the average program level is approxi­mately 1.23V rms (+4dBm), or 1.95V rms (+8dBm)
terminated by a 600-ohm line. The peak level may
extend to about +24dBm (12.3V rms). The line (high
level) input of professional audio equipment is
designed to accept levels on this order of magnitude
without overdrive (clipping distortion); most pro­fessional equipment can be driven to full output by
nominal +4dBm input (source) levels, although a few
units require +8dBm (1.95V rms) at their input to
yield full output. See the discussion of "Gain Overlap"
on Page FIVE 4.

Hi-fi type equipment operates at considerably lower
line levels than professional equipment (with exceptions),
usually at -16dB (0.123 volts) nominal levels. Notice we
use

the

expression "dB," not "dBm." This

"dBm" denotes a power level (relative to 1mW, or

0.775V rms across a 600-ohm impedance), whereas "dB"
denotes a voltage level (as defined in this manual) rela-

tive to 0.775V rms. This is a subtle distinction, and is

explained in greater detail in the Appendix on Page

EIGHT 1, and on Page THREE 1 of the specifications.

The nominal -16dB (0.123 volts) level of hi-fi

equipment is equal to 123mV rms (123 one-thousandths
of a volt) across a 10,000-ohm or higher impedance line.

Peak program levels may reach or slightly exceed +4dB
(1.23V rms across a high impedance line). Note that a

hi-fi unit capable of +4dB (1.23 volts) maximum output

into a high impedance,
for 600-ohm circuits with nominal +4dBm level require­ments. Thus, hi-fi equipment is usually incapable of

driving professional equipment to its full rated output,
at least not without first reaching a high level of
distortion. Moreover, when the output of hi-fi equip-

ment (which is almost always meant to be operated

into a high impedance) is connected directly to the low

impedance input of professional equipment, the hi-fi

unit "sees" a partial short circuit. This may overload the

hi-fi output, or it may simply drop the output level by a

few dB, depending on the circuitry. The P-2200's input

sensitivity and input impedance are high enough to allow

does

not

possess

is

because

adequate drive

its use with some hi-fi or semi-pro equipment, however
it's a good idea to check the specifications for each
situation. The point of this discussion, is that impedance
and level are extremely important considerations when
connecting audio equipment.

DYNAMIC RANGE

Every sound system has an inherent noise floor
which is the residual electronic noise in the system
equipment (or acoustic noise in a room). The effective
dynamic range of a system is equal to the difference
between the peak output level of the system and its

noise floor.

A concert with sound levels ranging from 30dB SPL
to 120dB SPL has a 90dB dynamic range. The electrical
signal level in the sound system (given in dB of voltage)

is proportional to the original sound pressure level (given
in dB SPL) at the microphone. Thus, when the program

sound levels reach 120dB SPL, maximum electrical

levels (at the mixer's output) might reach +24dB (12.3
volts), and maximum power output levels (at the
P-2200's
load. Similarly, where sound levels drop to 30dB SPL,

minimum electrical levels will drop to -66dB (0.388
milli-volts) and power levels will drop to 230 nano-watts

(230 billionths of a watt; these levels are not uncom­mon). The program still has an electrical dynamic range
of 90dB: [+24dB (12.3 volts)] - [-66dBm (0.388
micro-volts)] = 90dB. This dB to dB correspondence is
maintained throughout the sound system, from the
original source at the microphone, through the
electrical portion of the sound system, to the speaker
system output. A similar correspondence holds for any
other type of sound system, a recording studio system,
disco system or a broadcast system.

above sound system is +4dB (1.23 volts) corresponding
to an average sound level of 100dB SPL. This average
level is usually called the nominal program level. The

difference between the nominal and the highest (peak)

levels in a program is the headroom. In the above
example, the headroom is 120dB SPL -100dB SPL =
20dB (not 20dB SPL). Similarly, the electrical head-

room is [+24dB (12.3 volts)] - [+4dB (1.23 volts)] =
20dB (not 20dBm, see Appendix). This corresponds to a

power headroom which is also 20dB.
electronic noise floor of -56dB (1.23 millivolts), and

a peak output level of +18dB (6.16 volts), its dynamic

range would only be 74dB. If the original program has

a dynamic range of 90dB, then 16dB of the program is

lost in the sound system. There may be extreme clipping

of program peaks, some of the low levels may be buried

in the noise, or some of the program may be lost in both

ways. Thus, it is extremely important to use wide

dynamic range equipment, like the P-2200 and Yamaha

PM-Mixers, in a professional sound reinforcement system.
dynamic range is limited by the noise floor and

distortion levels of the tape itself, one way to avoid

these program losses due to clipping and noise is to

"compress" the program's dynamic range (see Page
SEVEN 3). A better way is to apply special "noise

reduction equipment" which allows the original program
dynamics to be maintained throughout the recording
and playback process. This improvement in the dynamic

range of recorded material again demands wide dynamic

range from every piece of equipment in the recording/

playback chain, including the power amplifier.

output)

Generally, the average electrical line level in the

In the above example, if the system had an

In the special case of a tape recorder, where the

might

reach

230

watts

into

an 8-ohm

NOTE: The P-2200 actually has a maximum signal to noise ratio of 110dB

(which is its dynamic range!. The SYSTEM'S Dynamic Range is limited by
acoustic noise at the mic input, for the system shown, and by the maximum
signal to noise ratio of the PM-700 Mixer (93dB), a very respectable figure for
a high gain device.

Fig. 33 - Dynamic Range in an Audio System

The P-2200 is designed for these wide dynamic range
applications. It has exceptionally low noise figures, and
high headroom capabilities (high power output). In
addition, its operating levels and impedances correspond

with professional requirements.

GAIN OVERLAP AND HEADROOM

Yamaha PM-Mixers have +24dB (12.3 volts) maximum
output levels. This high output level is advantageous in
many situations. One reason is that it assures adequate
headroom for driving the input of any professional
device. High headroom is also important for a mixer that
feeds a professional tape recorder, and in a concert

sound reinforcement system.

Occasionally a "passive" device (no transistors or
tubes) is inserted between the Mixer and the power
amplifier in a sound reinforcement system, or in a
studio monitoring system. Examples of passive devices
are passive graphic equalizers, passive low level crossovers

(frequency dividing networks), pads and resistive isola-

tion

networks.

Passive

devices

always attenuate the

signal

level somewhat. For example, a passive low level cross-

over, when properly terminated, creates a 6dB loss

between the mixer and the power amplifier. Passive
graphic equalizers can create more than 6dB loss at
some frequencies. A mixer with +24dB output drive,
such as a Yamaha PM-Mixer, has considerably more out-

put level than is needed to drive the inputs of most

amplifiers so that passive devices may be used as desired.
This extra output capability (above that needed to drive
the power amplifier) is known as "gain overlap," and is

one of the most important advantages of a Yamaha

PM-Mixer over other mixers, especially non-professional

mixers.

INPUT SENSITIVITY RATINGS

Some auxiliary devices have input sensitivities rated
like this: "nominal input sensitivity: +4dB." Others may
be

rated like

this:

"input

sensitivity: +4dB

for

rated
output." This later rating is typical of many power
amplifiers, including the P-2200. The difference between

these ratings is subtle, but very important. The first
device, has a nominal input sensitivity of +4dB (1.23
volts), and may be capable of peak levels far above +4dB

(1.23 volts); the actual headroom may be stated in

another specification. The second device (the P-2200 is
an example), has a peak input sensitivity of +4dB

(1.23 volts). A +4dB input signal to the P-2200 drives

it

to

full

output.

Thus, the

user

must

be

sure

to

care-

fully select the system's operating levels.

The gain overlap in mixer output drive capability and

power amp input sensitivity let the user choose a head-

room figure for the P-2200; this will be typically 10dB
for speech or concert reinforcement, 15 to 20dB for
high quality music reproduction or recording. The dis­cussion on Page SIX 5 illustrates the headroom adjust­ment process.

PROFESSIONAL EQUIPMENT ADVANTAGES

The many advantages of professional equipment
include: balanced lines for hum and noise rejection, low
impedance circuits for long cable runs, high operating
levels for maximum signal to noise ratio, high operating
headroom for low distortion and low noise, and reliable
XL-type connectors that are unlikely to be disconnected
accidentally and that tend not to hum or pop when
being attached. In addition, levels and impedances for
professional equipment are relatively standardized,

which, in many cases, eliminates the need for special

adapters, pads, transformers, or preamplifiers. For these
reasons,

professional

equipment,

even

though its

initial
cost may be higher, will almost always benefit the user
on a long term cost/performance basis.

The P-2200 user realizes all of these professional
benefits. In addition the P-2200 can be used with many
hi-fi or semi-pro devices, such as guitar preamps, semi­pro or hi-fi tape machines.

Fig. 34 - Typical Gains and Losses in a System

INSTALLATION AND DETAILED

OPERATION

PHYSICAL MOUNTING

Shelf Mounting

The P-2200 can be used on any surface, so long as

there is adequate ventilation. Do not remove the

P-2200's feet, since this would prevent air flow below

the amplifier.

Permanent Installation Rack Mounting

Mount the P-2200 in any standard 19" electronic
equipment rack as shown to the right. Leave adequate
space between the P-2200 and other devices in the rack
for ventilation, and for expected cabling. Cooling fans
may be required when the P-2200 must produce
extremely high average power output, or when it is
located in a high temperature environment, such as a
closed outdoor building in direct sunlight.

Rack Mounting for Portable Usage

Road cases must be durable enough to survive heavy
cartage, and airline travel. Brace the rear of the P-2200,
and if the road case is small and ventilation is con­stricted, install cooling fans. One possible design is
shown in Figure 35.

Front fan panel view before folding.

Rear fan air containment panel front view, before folding.

Fig. 35 - P-2200 with Cooling Fans

P-2200 mounted in rack showing support brackets

made from bent pieces of 1/8" steel rod with nuts

welded to their ends.

Regarding Input Impedance and Terminations

There is sometimes a misunderstanding regarding the
nature of matching or bridging inputs, the use of termi­nating resistors, and the relationship between actual

input impedance and nominal source impedance. Most
electronic outputs work well when "terminated" by an
input (connected to an input) having the same or a
higher actual impedance. Outputs are usually overloaded
when terminated by an impedance that is lower than the
source impedance. When the actual input impedance of
the following device is nearly the same impedance as the
source, it is known as a "matching" input. When the
input of the following device is ten times the source

impedance, or more, the input is considered to be a
"

bridging"

input.

There

is

hardly

any

loss

of signal
level when an input bridges the source device, but a
matching input may cause a loss of 3 to 6dB in level.
Such losses, however, are normal and usually present
no problem.

It seldom is necessary to place a 600 ohm "termin-

ating resistor" across any high impedance input (the

P-2200's input can be considered to be high impedance).
In fact, most 600-ohm outputs operate normally when
bridged by a high impedance; it is as though no load
were connected to the source device.

The only instance where a terminating resistor may
be required is when the manufacturer of the source
device specifically states that a terminating resistor is
necessary. In such cases, there is usually a special type
of output transformer in the source device, or the device
is constructed primarily of precision, passive com­ponents (no transistors or tubes), such as a passive
equalizer. In these cases, the terminating resistor assures
optimum frequency response in that device. Input

terminating resistors are not needed for the P-2200 to

operate correctly. If a 150 ohm or 600 ohm resistor is

specified for the source device, it should be installed at
the end of the cable nearest the P-2200 in order to

minimize possible hum, noise or signal losses in the cable.

Fig. 36A - The Actual Voltage reaching the Load Device

is given by the Formula: (also see Appendix)

Fig. 36B - Where to Insert a Termination Resistor when one

is required.

CABLING AND IMPEDANCE MATCHING
Attenuation Pads

A "pad" is a resistive network that lowers the level in

an audio circuit. The most common professionally used

pads are "T-pads" and "H-pads." T-pads unbalance true

balanced lines (and floating lines), but work well in
unbalanced circuits. H-pads are best for balanced or
floating lines, but should not be used in an unbalanced
circuit since they will insert a resistance in the return

lead (ground). For a discussion of other types of pads,

refer to the AUDIO CYCLOPEDIA by Howard M.
Tremain (Pub. Howard W. Sams).

Fig. 37 - Where to Install a Pad when one is required.

Always install a T-pad near the input of the device it
feeds, with as short a length of cable as possible on the
low level side of the pad. This maintains a high signal
level in the longer transmission cable, minimizing any
induced hum and noise.

The low impedance pad values illustrated in Figure 38
are designed for 600-ohm lines. Commercially manu­factured pads are available; consult your Yamaha dealer.

When connected between a 600-ohm or lower source

and a 600-ohm or higher termination, pad attenuation

values

will

remain

fairly

accurate. For higher impedance

circuits, resistor values must be changed. A 600-ohm pad

inserted in a high impedance circuit may overload the
device feeding the pad (the source device). Multiply the
given values by the output impedance of the source

device, and divide that answer by 600 to achieve the
desired value. The high impedance values listed for the
T-pads in Figure 38 are close approximations of average
hi-fi pads, based on 10,000-ohm nominal impedances.

For low level circuits, use 1/4 watt resistors. For out­puts with continuous sine wave levels above +24dBm,
use 1/2 watt resistors; for continuous sine wave levels

180k

82k
43k
27k

22k

16k

13k

11k
9100

8200
6800

5100
4300

3300

2700

2000

1500

1300

1000
820
620
510
390
330

240
200
62

R2

10k

5.1k

2.7k

1.6k

1.2k

1k

820
680
560
470

430
360

240
200
150

120

91

75
62
47

36
30
22

18
15
12

3.6

dB Loss

0.5

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0
10
12

14
16
18

20
22
24

26
28
30
32
34
36
38
40

50

R1 T (ohms)

300

16

560

33

1100

68

1710

100

2200

130

2700

160

3300

200

3900

220

4300

270

4700

270

5100

300

6200

360

6800

390

7500

430

7500

470

8200

510
510

8200

9100

510

9100

560

9100

560

9100

560

9100

560
560

10k
10k

560

10k

560
560

10k
10k

620

R1 H (ohms)

150

8.2

300

18

560

33

820

51

1100

68

1500

82

1600

100

2000

110

2200

130

2400

150

2700

150

3000

180

3300

200

3600

220

3900

220

3900

240

4300

240

4300

270

4700

270

4700

270
270

4700

300

4700
4700

300
300

4700
4700

300

5100

300

5100

300

Fig. 38 - Attenuation Pad Construction and Resistor Values

for High Impedance (10K-ohm) and Low Impedance (600 ohm)

[shaded area) circuits.

Fig. 39A - Pads Constructed in Mini-Boxes.

Transformers

Audio transformers (as distinguished from power
supply transformers, RF transformers or other trans­formers) are primarily used for ground isolation,
impedance matching and level matching. The following

paragraphs detail several applications of audio trans­formers at low signal levels. Speaker-level transformers

are discussed on Page SEVEN 6; the Appendix gives
further details on transformer operation.

Matching Transformer Box:

Impedance matching transformers can be used to
connect a high impedance source to a low impedance
load, or vice-versa (see Page SIX 5 for a discussion of
matching versus bridging inputs). The box shown below

may be used to run a 600-ohm balanced or floating line
to the P-2200 input, or it may be used between any
600-ohm source and high impedance input. Use a trans­former capable of handling nominal +4dB (1.23V)
inputs with at least +24dB (12.3V) peak capability.

The transformer should be mounted in a mini-box,
wired to the XLR connectors with stranded wire, and
connected to the auxiliary equipment with one of the
cables previously illustrated. In line transformers, such
as those manufactured by Shure Brothers, Sescom, and
others may be used, with suitable adapters.

above +30dBm, use 1 watt, low inductance resistors.

10% tolerance is acceptable for most pads.

Fig. 39B - Pad Constructed in Switchcraft Model S3FM

It is possible to construct a pad within an XLR con-

nector, but the extremely tight fit can adversely affect
reliability. The Switchcraft model S3FM is a tube with a
male A3M (XLR) at one end, and a female A3F (XLR)

at the other end. Pads using 1/4 watt resistors can be

constructed inside this device. Cover the entire pad with

insulation tubing before final assembly into the S3FM.

A "mini-box" fitted with male and female XLR con­nectors is an easy to build, rugged housing for a pad.
Use stranded wire for best results.

Illustrated are three typical pad construction tech-

niques. For most applications, it will be sufficient to

construct only a few types of pads: 20dB, 24dB, and
40dB pads cover almost any requirement. Consult

Figures 37, 38 and 39 for schematic, construction and
resistor value information.

Fig. 40 - Matching Transformer Box

Step Up Transformer Box

The step up transformer box illustrated here is
similar to a pair of matching transformer boxes. This
configuration provides voltage step-up for optimum
drive levels when connecting the output of a low
impedance, low level source, such as the headphone

output of a mixer, to the two inputs of the P-2200. It

has a stereo phone jack input, but if the input source is
monaural, the transformer lead to the ring of the T.R.S.
input jack may be moved to the jack's tip so that a
standard T.S. phone plug input will feed both transfor­mers.

Alternately,
T.S. phone jack inputs, or with XLR inputs. Two
standard (2-wire) phone jacks outputs are provided for
connection

P-2200. Construct two cables from dual conductor,
shielded cable and T.S. phone plugs to connect the
transformer box output to the P-2200's input. Locate
the step up transformer box at least 5 feet from the
P-2200 to avoid hum pickup from the amplifier's power

transformer. However, the cables from the transformer
box to the amplifier should be no longer than 10 feet,
since this is a high impedance circuit. Use low

capacitance, coaxial, hi-fi type cable between the box

to

the box may

the "left"

be

and "right"

built

inputs

with

of

separate

the

and the amplifier. Since the inputs of the P-2200 are
unbalanced, connecting two cables to its input forms
a short ground loop as shown in Figure 60 (see dis­cussion of grounding on Page SIX 13). To keep hum

pickup at a minimum, run the two cables close

together; this minimizes the area (and therefore the

hum) enclosed by the loop.

The two diagrams show circuits using a Triad A-65J
transformer, and a UTC A-24 transformer. Similar 600
ohm to 15K-ohm transformers are acceptable. The 1/4
watt, 10%, 15K-ohm resistors are used to terminate the
transformers, for lower distortion, and improved
frequency response.

Bridging Transformer Box

When a single, low impedance, balanced source which

must remain balanced feeds several P-2200 inputs, the

TRANSFORMER AVAILABILITY

The matching and step-up transformers mentioned

in the preceding subsections are available from many
electronic parts dealers. Yamaha does not endorse
specific products by citing them herein; rather, these
transformers are mentioned for convenience only. If
you are unable to locate the transformers from your

local electronic parts dealer, contact the manufacturer

at the address shown below.

Sescom, Inc.

P. 0. Box 590, Gardena, CA 90247
Phone [phone] [phone]

Shure Brothers, Inc.

222 Hartrey Ave., Evanston, Illinois 60204
Phone [phone] Cable: SHUREMICRO

Triad
305 N. Briant St., Huntington, Indiana 46750
Phone [phone] TWX: 816-333-1532

UTC
150 Varick St., New York. NY 10013

Phone [phone] TWX: 710-581-2722

A line of very high quality transformers, suitable for the

most critical applications, is available directly from:

Jensen Transformer Company

10735 Burbank Blvd., North Hollywood, CA91601

Phone [phone]

Fig. 41 - Step-Up Transformer Box

bridging transformer box should be used. While matching
or step up transformers like those just described would

maintain a balanced feed, several such boxes could over­load the source device. By using a transformer which has
a high impedance primary and a high impedance

secondary, the source can feed several P-2200 inputs

without being overloaded. Use one box for each
P-2200 input, paralleling the primaries (the primaries

are then fed from the single, balanced source; the
secondaries are connected to the P-2200 inputs). Con­struct the box in a similar manner to the Step Up
Transformer Box, or the Matching Transformer Box.

Fig. 42 - Bridging Transformer Box Schematic. Construction

is similar to Photos in Figures 40 or 41.

Input Impedance Matching for the P-2200

While the input impedance of the P-2200 varies
somewhat with the setting of the input attenuator, for
practical purposes, it is fixed at 25K-ohms. This means
that any source device feeding the P-2200 must be
capable of driving a 25K-ohm load without overload,
distortion, or failure. Any professional device, most
semi-pro equipment, and most hi-fi devices meet this
requirement.

When a single source device feeds the inputs of
several P-2200 amplifier sides, the effective load on the
source is equal to the parallel combination of all the
P-2200 input impedances. To avoid overloading a high
impedance source, use a resistor matching network, an
impedance matching transformer, or insert a line
amplifier with a lower output impedance between the
source and the P-2200's input.

Figure 43 shows the voltage division diagrams for
the output impedance of a source device and the input
impedance of the P-2200, when various impedance
matching devices are used.

Level Matching and Headroom (also see Page FIVE 2)

Headroom is the amount of level available above the
average (nominal) signal for peaks in the program. Noise
floor is the average noise level at any point in the
system. The difference in level between the peak output
of the system and its noise floor is the system dynamic
range.

Careful level matching can optimize the dynamic range
of the system (minimize the noise) and maximize the
headroom.

First choose a headroom figure. For maximum fidelity

when reproducing music, it is desirable to allow 20dB of

headroom

above

the

average

system

output.

While

some
extreme musical peaks exceed 20dB, the 20dB figure is
adequate for most programs. A 20dB headroom figure
represents a peak level that is one hundred times as
powerful as the average program level. This means that
for an 8-ohm load, and a 20dB headroom figure, even an

amplifier as powerful as the P-2200 has to operate at an
average 2.3 watts output power. In some systems such as
studio monitoring, where fidelity and full dynamic range
are of utmost importance, this low average power may

be adequate. In other situations, such as 70-volt back-

ground music systems, a 20dB headroom figure is
undesirable and costly.

The choice of a headroom figure, then. depends on

the type of program material, the application, and the

available budget for amplifiers. For a musical applica-

tion where high fidelity is the uppermost consideration,

15 to 20dB of headroom is desirable. For most sound
reinforcement applications, especially with large
numbers of amplifiers, economics play an important
role, and a 10dB headroom figure is usually adequate.
For

these

applications, a limiter

will

help

hold

program
peaks within the chosen headroom level, and thus avoid
clipping problems. For the extreme situation where
background music and paging must be heard over high
continuous noise levels, such as a factory, yet danger­ously high sound pressure levels must be avoided, a head-

room figure of as low as 5 or 6dB is not unusual. With
this low headroom figure, and the extreme amount of
compression and

limiting

necessary

to

achieve

it

without
distorting, the program may sound unnatural, but the
message

will

get

through.

Fig. 43 - Voltage Division Diagrams

Fig. 44 - Headroom Adjustments

After choosing a headroom figure, next adjust the
incoming and outgoing signal levels at the various
devices in the system to achieve that figure. For the
simple system in Figure 44, the adjustments for a 20dB
headroom figure would be made as follows:

1. Initially, set the attenuators on the P-2200 at
maximum attenuation (maximum counter clockwise
rotation). Feed a sine wave signal at 1000Hz to the
mixer input at an expected average input level

approximately -50dB (2.45mV) for a microphone,
+4dB (1.23 volts) for a line level signal. The exact volt­age is not critical, and 1000Hz is a standard reference
frequency, but any other appropriate frequency can
be used.

2. Set the input channel level control on the mixer
at its rated "nominal" setting, and adjust the master
level control so that the output level is 20dB below the
rated maximum output level for the mixer. For the
Yamaha PM-180 Mixer used in the example, the
maximum rated output level is +24dB (12.3 volts), so
the output level should be adjusted to +4dB (1.23
volts), as indicated either on an external voltmeter, or
on the mixer's VU meter (0VU).

3. Assume that the rated maximum input level for

the graphic equalizer in the example is +14dB (3.88

volts). Subtracting +4dB from +14dB leaves only 10dB

of headroom, so a 10dB resistive pad must be inserted
between the mixer output and equalizer input. Now, the
signal

level

at the

input

to

the equalizer should

be

-6dB

(388mV), which can be confirmed with a voltmeter.

4. Assume that the maximum rated output level of
the equalizer in this example is +18dB (6.16 volts).
Adjust the master level control on the equalizer so that
the output level is 20dB below this rated maximum, or

-2dB (616mV). Since the equalizer has no VU meter,
you need an external voltmeter to confirm this level.

5. Finally, starting with the attenuators on the
P-2200 at maximum attenuation (maximum counter
clockwise rotation), slowly rotate them clockwise,
watching the peak reading meters. When the peak

reading meters indicate 2.3 watts output from the
P-2200, there is 20dB headroom left before clipping.

To operate this system, use only the controls on the
mixer, and avoid levels that consistantly peak the mixer's
VU

meter

above

the

"zero"

mark on its

scale,

or

that
peak the P-2200's meters above a safe power level for
the speaker system. Any adjustments of the other devices
in the system will upset the headroom balance. However,
the P-2200's calibrated attenuators allow easy setups
and quick changes, if you decide to change the headroom
figure. They also allow you to momentarily fade the
entire program or a single channel and to later bring it
back up to exactly the same level.

To use this technique with any system, first design
the required speaker system, and calculate the number
of power amplifiers needed to safely operate the
speaker system with adequate headroom. Then, choose
the mixer, and other devices that feed the power
amplifiers, and set up the system according to the above
instructions.

In some cases, it may be useful to set up different
headroom figures in different parts of a complex
system. For example, background music and paging
should be severely compressed in a noisy lobby area,
but the same program material would sound more
natural in less noisy office and auditorium areas of the
same installation if the headroom figure were increased.

By placing a compressor/limiter in the circuit just before
the P-2200 that feeds the lobby areas, the headroom
figure can be lowered for that section only, without
affecting other parts of the system.

Cabling the System

Audio circuits may be divided into the following

classifications (by signal level):

1. Low level circuits: any circuit carrying signals of

-80dB (77.5 microvolts) to -20dB (77.5 millivolts),
example: microphone lines.

2. Medium or line level circuits carrying signals of

-20dB (77.5mV) to +30dB (24.5 volts), example:
mixer outputs.

3. High level circuits carrying signals above +30dB

(24.5 volts), example: speaker lines.

4. AC power circuits, including lighting circuits.

5. DC control (or supply) cables to relays, from

batteries, etc.

Generally, each of these categories should be
physically separated from the others to avoid crosstalk,
oscillation, and noise spikes. One possible exception is
that DC control or supply cables and line level signal
cables can be routed together if the DC signal is
adequately filtered. Figure 45 shows the undesirable

results that can occur if line or speaker cables are placed
near microphone cables. This situation occurs in concert
sound when mixer outputs and mic inputs feed through
the same "snake" cable.

Fig. 45 - Example of Crosstalk

Figure 46 shows an equipment rack with a good
cable layout. Note that the different categories of cable
are carefully separated, and that where it is necessary
to cross two categories, they cross perpendicular to each
other. These suggestions apply to all types of systems,
portable as well as permanent.

Fig. 46 - Cable Routing in Equipment Rack. (Reprinted
from Sound System Engineering by Don & Carolyn Davis
published by H. W. Sams Co.)

Figure 47 shows the rear of a P-2200 amplifier with

its two inputs "chained" using a phone-to-phone cable.

In this mode, the signal fed to the first side is also fed to
the second side of the amplifier. This could also be
accomplished with an XLR-to-XLR cable.

For low and medium level balanced signal cables, use

good quality twisted pair shielded cable. For portable

use, a cable with rubberized insulation and braided
shield

(such

as

Belden #8413 or #8412) will handle

easily and survive road abuse; for permanent wiring,

a vinyl insulated cable with a foil shield (such as
Belden #8451) is easier to strip for terminations, and
it

pulls through conduits

Fig. 47 - "Chaining" of Inputs

with

less

drag.

For unbalanced, signal level cables, use low capaci­tance shielded cable with a good quality (high percentage
density) shield. Again, rubberized types work best for
portable use, vinyl types with foil shields are acceptable
for permanent installations (the foil shield may crack
and split under the constant flexing of portable usage).
Many single conductor shielded cables have an extremely
fragile center conductor. To avoid this problem, use a
higher quality dual conductor cable and ground one
center conductor.

For high level speaker cables and DC control cables,
use heavier gauge cable. The chart in Figure 48 shows
the effects of different sized wired gauge on power
losses in speaker cable. Except in extreme RF fields
(radio frequency interference), speaker and control

cables will not need shields; when they do, use heavy-

gauge shielded cable, or place the cables in steel or
aluminum conduit.

*Approximate. depends on wire type.

Fig. 48 - Chart showing the effects of different Sized

Wired Gauge on Power Losses in Speaker Cable.

Connectors

In

many

cases,

connectors

will

be

dictated by the
types of equipment in the system. When you can make
choices, the following guidelines may help.

Phone Connectors are an audio industry standard con­nector used for signal and speaker lines. T.S. (tip/sleeve)
types, like those used as inputs on the P-2200, are used
for unbalanced signals; T.R.S. (tip/ring/sleeve) types are
used for balanced signals, or for stereo unbalanced

signals such as stereo headphones. Phone connectors are

generally easy to wire, and the metal types provide good

shielding. However, for high power applications, such as
the output of the P-2200, many phone plugs do not

have rated current capacities high enough to avoid some
power loss. Also, some phone plugs have a brittle
insulator between the tip and sleeve which can break if

the connector is dropped, resulting in a tip to sleeve

connection which is a direct speaker line short circuit.

For this reason, phone jacks have not been used for the

P-2200 output. If you have an amplifier with a phone

jack

output,

military

grade

phone connectors,

while
more expensive and somewhat harder to wire, are the
best choice for avoiding these problems.

Phono Connectors are not usually considered pro­fessional, and are not included on the P-2200. If phono
connectors are part of a system, they should be the
higher quality types with a separate cover such as
Switchcraft#3502.

XLR Connectors are another audio industry standard.
They come in several configurations for different types
of cabling, and can be used for either balanced or un-

balanced connections. Three wire types, like those used
as inputs on the P-2200, are the most common. XLR
connectors are generally very durable, and are well
shielded. The three wire types have the added
advantage that pin#1 always connects before pin

#2 or #3 so that the ground or shield wire connects

before the signal carrying wires. This allows any static
charges built

up on the shields

to

equalize before

the

signals meet, reducing pops in the system.
Banana jacks are common in the audio industry, and are

a standard connector for test equipment. They do not
provide any shield, and can be reversed in their socket.

However, banana jacks, like those used as output
connectors on the P-2200, have high current ratings,
and are good speaker connectors, especially inside an
equipment rack where occasional disconnections must
be made.

Other Connectors are occasionally used in audio work.
Standard, electrical twist-lock types have been used for
speaker connections, although there is always the
dangerous possibility of a mistaken connection to an

AC power line. Multi-pin "snake" connectors are
common for low level signals, but may be fragile and
need careful handling. For permanent installations, and

for permanent connections in portable equipment racks,
crimp type (as opposed to solder type) spade lugs and
terminal strips may actually provide the best type of

connection since a properly crimped connection is more

reliable, and lower impedance than a solder connection.

A "hard wire" or direct connection is also reliable and

low impedance if properly made.

The preparation of complete cables, with connectors

properly installed, is the key to reliable and trouble-free

operation of any sound system. For this reason, the fol­lowing illustrations are included. Experienced audio

technicians may wish to review these illustrations, even

if they already know how to wire connectors. A few
moments of extra care here can save hours of trouble­shooting later on.

As a rule, the amount of insulation removed and the
length of exposed cable should be minimized. This
reduces the likelihood of short circuits and improves the
ability of the clamp to grip the cable firmly. Enough

heat should be used to obtain a free flow of solder, but
allow leads to cool quickly after solder flows to avoid
melting insulation. After each connector has been com-

pletely wired, the cable should be tested with an ohm­meter or a cable tester. Continuity between the various
conductors and their associated connector pins must be
established, and there should
open

circuit)

between all

be infinite

connector

resistance

pins.

In

most

(an

cases,
especially in portable installations, XLR connectors
should not conduct at all between the shell and pin 1.
This avoids grounding problems from inadvertent touch-

ing of the shell to other devices.

Cables to be connected to terminal strips should be

prepared by stripping the ends and installing crimp-on
or preferably, solder type lugs. If there is any chance
the cable will be strained, use a cable that is constructed
with internal strain relief cord, such as Belden No. 8412.

Crimp a lug onto the cord, and secure the lug to an un-

used terminal. (The cord should be drawn slightly
tighter than the wire leads in order to take the strain

first.)

WIRING AN RCA-TYPE PIN PLUG*

Parts identification and cable preparation.

Strip approximately 1/2" of outer insulation. Unwrap
or unbraid the shield and form a lead. Strip approxi­mately 5/16" of insulation from the center conductor.
Tin both leads.

Solder the shield to the outer surface of the shell
connection, allowing enough free shield to wrap the
cable around to the center of the connector. Cool
the connection immediately with pliers.

Insert the center conductor in the hollow pin, and

fill

that

end

with

solder. Cool the connection immedi-

with

pliers.

Clean

ately

any solder

splashes

and

inspect

for burned insulation. Pinch the clamp around the outer

insulation with pliers, firmly, but not so tight as to cut
the insulation.

Slide the shell forward and screw it tightly to the

threaded plug.

*Switchcraft No. 3502 connector illustrated. Many large
diameter cables are more easily wired to "simple" RCA
type

pin

plugs

equivalent). The braid can then be soldered directly to the

without a shell

shell of the plug.

(Switchcraft

No. 3501M,

or