Crown Audio STUDIO AMPLIFIER User Manual

®

THE PROFESSIONAL AUDIO DIVISION OF CROWN INTERNATIONAL, INC.

®

®

Exported to select countries as Amcron.

Studio Reference

PROFESSIONAL STUDIO AMPLIFIERS

OWNER’S MANUAL

©1995 by CROWN INTERNATIONAL, INC.

P.O. Box 1000, Elkhart, Indiana 46515-1000

Telephone: [phone]

Trademark Notice:

are trademarks and
Crown International, Inc. Other trademarks are the property of their respective owners.

Studio Reference

Crown

,®

IOC

®

,

,™

ODEP

Smart Amp

®

,

™

,

IQ System

MPX-6

®

and

,™

SMX-6

,™

AMB-5

®

P.I.P.

are registered trademarks of

,™and

grounded bridge

™

Printed on

recycled paper.

™

K80604-0

8/95

3

YEAR

THREE YEAR

FULL WARRANTY

3

A

E

Y

R

WORLDWIDE

The Crown Audio Division of Crown International, Inc., 1718 West
Mishawaka Road, Elkhart, Indiana 46517-4095 U.S.A. warrants to you,
the ORIGINAL PURCHASER and ANY SUBSEQUENT OWNER of each
NEW Crown
purchase by the original purchaser (the “warranty period”) that the new
Crown product is free of defects in materials and workmanship, and we
further warrant the new Crown product regardless of the reason for
failure, except as excluded in this Crown Warranty.

1

Note: If your unit bears the name “Amcron,” please substitute it for the

name “Crown” in this warranty.

ITEMS EXCLUDED FROM THIS CROWN WARRANTY

This Crown Warranty is in effect only for failure of a new Crown product
which occurred within the Warranty Period. It does not cover any product
which has been damaged because of any intentional misuse, accident,
negligence, or loss which is covered under any of your insurance
contracts. This Crown Warranty also does not extend to the new Crown
product if the serial number has been defaced, altered, or removed.

We will remedy any defect, regardless of the reason for failure (except as
excluded), by repair, replacement, or refund. We may not elect refund
unless you agree, or unless we are unable to provide replacement, and
repair is not practical or cannot be timely made. If a refund is elected, then
you must make the defective or malfunctioning product available to us
free and clear of all liens or other encumbrances. The refund will be equal
to the actual purchase price, not including interest, insurance, closing
costs, and other finance charges less a reasonable depreciation on the
product from the date of original purchase. Warranty work can only be
performed at our authorized service centers. We will remedy the defect
and ship the product from the service center within a reasonable time after
receipt of the defective product at our authorized service center. All
expenses in remedying the defect, including surface shipping costs to the
nearest authorized service center, will be borne by us. (You must bear the
expense of all taxes, duties and other customs fees when transporting the
product.)

You must notify us of your need for warranty service not later than ninety
(90) days after expiration of the warranty period. All components must be
shipped in a factory pack. Corrective action will be taken within a
reasonable time of the date of receipt of the defective product by our
authorized service center. If the repairs made by our authorized service
center are not satisfactory, notify our authorized service center
immediately.

DISCLAIMER OF CONSEQUENTIAL AND INCIDENTAL

YOU ARE NOT ENTITLED TO RECOVER FROM US ANY
INCIDENTAL DAMAGES RESULTING FROM ANY DEFECT IN THE
NEW CROWN PRODUCT. THIS INCLUDES ANY DAMAGE TO
ANOTHER PRODUCT OR PRODUCTS RESULTING FROM SUCH A
DEFECT.

No person has the authority to enlarge, amend, or modify this Crown
Warranty. This Crown Warranty is not extended by the length of time
which you are deprived of the use of the new Crown product. Repairs and
replacement parts provided under the terms of this Crown Warranty shall
carry only the unexpired portion of this Crown Warranty.

We reserve the right to change the design of any product from time to time
without notice and with no obligation to make corresponding changes in
products previously manufactured.

No action to enforce this Crown Warranty shall be commenced later than
ninety (90) days after expiration of the warranty period.

THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERS

CONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.

Telephone: [phone]. Facsimile: 219-294-8301

SUMMARY OF WARRANTY

1

product, for a period of three (3) years from the date of

WHAT THE WARRANTOR WILL DO

HOW TO OBTAIN WARRANTY SERVICE

DAMAGES

WARRANTY ALTERATIONS

DESIGN CHANGES

LEGAL REMEDIES OF PURCHASER

9/90

NORTH AMERICA

The Crown Audio Division of Crown International, Inc., 1718 West Mishawaka
Road, Elkhart, Indiana 46517-4095 U.S.A. warrants to you, the ORIGINAL
PURCHASER and ANY SUBSEQUENT OWNER of each NEW Crown
product, for a period of three (3) years from the date of purchase by the original
purchaser (the “warranty period”) that the new Crown product is free of defects
in materials and workmanship, and we further warrant the new Crown product
regardless of the reason for failure, except as excluded in this Crown Warranty.

ITEMS EXCLUDED FROM THIS CROWN WARRANTY

This Crown Warranty is in effect only for failure of a new Crown product which
occurred within the Warranty Period. It does not cover any product which has
been damaged because of any intentional misuse, accident, negligence, or
loss which is covered under any of your insurance contracts. This Crown
Warranty also does not extend to the new Crown product if the serial number
has been defaced, altered, or removed.

We will remedy any defect, regardless of the reason for failure (except as
excluded), by repair, replacement, or refund. We may not elect refund unless
you agree, or unless we are unable to provide replacement, and repair is not
practical or cannot be timely made. If a refund is elected, then you must make
the defective or malfunctioning product available to us free and clear of all liens
or other encumbrances. The refund will be equal to the actual purchase price,
not including interest, insurance, closing costs, and other finance charges less
a reasonable depreciation on the product from the date of original purchase.
Warranty work can only be performed at our authorized service centers or at
the factory. We will remedy the defect and ship the product from the service
center or our factory within a reasonable time after receipt of the defective
product at our authorized service center or our factory. All expenses in
remedying the defect, including surface shipping costs in the United States, will
be borne by us. (You must bear the expense of shipping the product between
any foreign country and the port of entry in the United States and all taxes,
duties, and other customs fees for such foreign shipments.)

You must notify us of your need for warranty service not later than ninety (90)
days after expiration of the warranty period. All components must be shipped
in a factory pack, which, if needed, may be obtained from us free of charge.
Corrective action will be taken within a reasonable time of the date of receipt
of the defective product by us or our authorized service center. If the repairs
made by us or our authorized service center are not satisfactory, notify us or
our authorized service center immediately.

DISCLAIMER OF CONSEQUENTIAL AND INCIDENTAL DAMAGES

YOU ARE NOT ENTITLED TO RECOVER FROM US ANY INCIDENTAL
DAMAGES RESULTING FROM ANY DEFECT IN THE NEW CROWN
PRODUCT. THIS INCLUDES ANY DAMAGE TO ANOTHER PRODUCT OR
PRODUCTS RESULTING FROM SUCH A DEFECT. SOME STATES DO

NOT ALLOW THE EXCLUSION OR LIMITATIONS OF INCIDENTAL OR
CONSEQUENTIAL DAMAGES, SO THE ABOVE LIMITATION OR
EXCLUSION MAY NOT APPLY TO YOU.

No person has the authority to enlarge, amend, or modify this Crown Warranty.
This Crown Warranty is not extended by the length of time which you are
deprived of the use of the new Crown product. Repairs and replacement parts
provided under the terms of this Crown Warranty shall carry only the unexpired
portion of this Crown Warranty.

We reserve the right to change the design of any product from time to time
without notice and with no obligation to make corresponding changes in
products previously manufactured.

THIS CROWN WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, YOU
MAY ALSO HAVE OTHER RIGHTS WHICH VARY FROM STATE TO
STATE. No action to enforce this Crown Warranty shall be commenced later
than ninety (90) days after expiration of the warranty period.

THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERS

CONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.

Telephone: [phone]. Facsimile: 219-294-8301

SUMMARY OF WARRANTY

WHAT THE WARRANTOR WILL DO

HOW TO OBTAIN WARRANTY SERVICE

WARRANTY ALTERATIONS

DESIGN CHANGES

LEGAL REMEDIES OF PURCHASER

9/90

The information furnished in this manual does not include all of the details of design, production, or variations of the
equipment. Nor does it cover every possible situation which may arise during installation, operation or
maintenance. If your unit bears the name “Amcron,” please substitute it for the name “Crown” in this manual. If you
need special assistance beyond the scope of this manual, please contact our Technical Support Group.

Crown Audio Division Technical Support Group

57620 C.R. 105, Elkhart, Indiana 46517 U.S.A.

Phone: [phone] (U.S.A.) or 219-294-8200 Fax: [phone]

IMPORTANT

STUDIO REFERENCE AMPLIFIERS

REQUIRE CLASS 1 OUTPUT WIRING.

C A U T I O N

RISK OF ELECTRIC SHOCK

DO NOT OPEN

TO PREVENT ELECTRIC SHOCK DO

NOT REMOVE TOP OR BOTTOM
COVERS. NO USER SERVICEABLE
PARTS INSIDE. REFER SERVICING
TO QUALIFIED SERVICE PERSON-

NEL. DISCONNECT POWER CORD

BEFORE REMOVING REAR INPUT

MODULE TO ACCESS GAIN SWITCH.

WARNING

TO REDUCE THE RISK OF ELECTRIC

SHOCK, DO NOT EXPOSE THIS

EQUIPMENT TO RAIN OR MOISTURE!

A V I S

RISQUE DE CHOC ÉLECTRIQUE

N’OUVREZ PAS

À PRÉVENIR LE CHOC

ÉLECTRIQUE N’ENLEVEZ

PAS LES COUVERTURES.

RIEN DES PARTIES

UTILES À L’INTÉRIEUR.

DÉBRANCHER LA BORNE

AVANT D’OUVRIR LA

MODULE EN ARRIÈRE.

Magnetic Field

CAUTION! Do not locate sensitive high-gain equip­ment such as preamplifiers or tape decks directly
above or below the unit. Because this amplifier has

a high power density, it has a strong magnetic field
which can induce hum into unshielded devices that
are located nearby. The field is strongest just above
and below the unit.

If an equipment rack is used, we recommend locating
the amplifier(s) in the bottom of the rack and the
preamplifier or other sensitive equipment at the top.

WATCH FOR THESE SYMBOLS:

The lightning bolt
triangle is used to
alert the user to the
risk of electric shock.

The exclamation point
triangle is used to alert the
user to important operating or
maintenance instructions.

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CONTENTS

1 Welcome.......................................................................... 7

1.1 Features ................................................................... 7

2 Facilities .......................................................................... 8

3 Installation..................................................................... 10

3.1 Mounting ................................................................ 10

3.2 Cooling ................................................................... 10

3.3 Wiring ..................................................................... 11

3.3.1 Stereo (Two-Channel) Operation ................... 12

3.3.2 Bridge-Mono Operation ................................ 12

3.3.3 Parallel-Mono Operation ............................... 13

3.3.4 Input Connection .......................................... 14

3.3.5 Output Connection ....................................... 16

3.3.6 Additional Load Protection ............................ 18

3.4 AC Mains Power ..................................................... 18

4 Operation....................................................................... 19

4.1 Precautions ............................................................. 19

4.2 Indicators................................................................ 19

4.3 Protection Systems ................................................. 20

4.3.1

ODEP ...........................................................

4.3.2 Standby Mode .............................................. 21

4.3.3 Transformer Thermal Protection .................... 21

4.3.4 Circuit Breaker ............................................. 22

4.4 Controls .................................................................. 22

4.5 Filter Cleaning ......................................................... 23

5 Technical Information ................................................... 24

5.1 Overview ................................................................ 24

5.2 Circuit Theory ......................................................... 24

5.2.1 Stereo Operation .......................................... 24

5.2.2 Bridge-Mono Operation ................................ 26

5.2.3 Parallel-Mono Operation ............................... 26

6 Specifications ................................................................ 27

7 AC Power Draw & Thermal Dissipation........................ 36

8 Accessories ................................................................... 38

8.1

P.I.P.

Modules ......................................................... 38

9 Service........................................................................... 40

9.1 Worldwide Service .................................................. 40

9.2 North American Service .......................................... 40

9.2.1 Service at a North American Service Center .. 40

9.2.2 Factory Service ............................................ 40

21

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ILLUSTRATIONS

1.1

Studio Reference

2.1 Front Facilities ................................................................. 8

2.2 Rear Facilities ................................................................. 9

3.1 Mounting Dimensions .................................................... 10

3.2 Removing an End Cap .................................................. 10

3.3 Top View of a Rack-Mounted Unit .................................. 10

3.4 Proper Air Flow with a Rack-Mounted Blower ................ 11

3.5 Stereo Wiring ................................................................ 11

3.6 Bridge-Mono Wiring ...................................................... 12

3.7 Parallel-Mono Wiring ..................................................... 13

3.8 Unbalanced Input Wiring ............................................... 14

3.9 Balanced Input Wiring ................................................... 14

3.10 Balanced and Unbalanced Phone Plugs ....................... 14

3.11 Subsonic Filter Capacitors ............................................ 15

3.12 Unbalanced RF Filters ................................................... 15

3.13 Balanced RF Filters ....................................................... 15

3.14 Wire Size Nomograph ................................................... 16

3.15 Inductive Load (Transformer) Network ........................... 17

3.16 Loudspeaker Fuse Nomograph ..................................... 18

4.1 Indicators...................................................................... 19

4.2

Studio Reference

4.3 Removing a Handle ...................................................... 22

4.4 Meter Switches ............................................................. 23

4.5 Input Sensitivity and Ground Lift Switches ..................... 23

5.1 Circuit Block Diagram ................................................... 25

6.1

Studio Reference

6.2

Studio Reference

6.3

Studio Reference

6.4

Studio Reference

6.5 Typical Frequency Response ........................................ 33

6.6 Typical Damping Factor ................................................ 33

6.7 Typical Output Impedance ............................................ 33

6.8 Typical Phase Response ............................................... 34

6.9 Typical Common Mode Rejection .................................. 34

6.10 Typical Crosstalk ........................................................... 35

7.1

Studio Reference

Thermal Dissipation at Various Duty Cycles ................... 36

7.2

Studio Reference

Thermal Dissipation at Various Duty Cycles ................... 37

8.1 Installing a

I Amplifier ........................................... 6

Indicator States .................................. 20

I Minimum Power Matrix .................... 29

II Minimum Power Matrix .................. 30

I Maximum Power Matrix ................... 31

II Maximum Power Matrix ................. 32

I Power Draw, Current Draw and

II Power Draw, Current Draw and

P.I.P.

Module ............................................... 38

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Fig. 1.1 Studio Reference I Amplifier

Unpacking Instructions

Please unpack and inspect your new amplifier for
any damage that may have occurred during transit.
If damage is found, notify the transportation com­pany immediately. Only you, the consignee, may ini­tiate a claim for shipping damage. Crown will be
happy to cooperate fully as needed. Save the ship­ping carton as evidence of damage for the shipper’s
inspection.

Even if the unit arrived in perfect condition, as most
do, save all packing materials so you will have them
if you ever need to transport the unit. NEVER SHIP

THE UNIT WITHOUT THE FACTORY PACK.

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1 Welcome

The stunning realism you will experience when listen­ing to a Crown

Studio Reference

redefine your expectations. The evolution of this studio
standard ushers in a new era of powerful, ultraquiet
amplifiers capable of faithfully reproducing the most
demanding signals that state-of-the-art 20-bit digital
recording systems can offer. This kind of sonic integrity
does not happen accidentally. It demands the leader­ship and technical excellence for which Crown has
long been known.

With the best transfer function in the industry, ultra-high
dynamic range and extraordinary damping factor, your

Studio Reference

amplifier comes closer to the ideal
“straight wire with gain” than any other amplifier. As
you listen, it will become apparent—the amplifier’s low­frequency transient response is the standard by which
all others must be judged.

We have taken great care at every step in the creation
of your amplifier—from the selection of its components
to the routing of each wire. It is our goal to provide you
with total satisfaction. This is one reason why we have
spent considerable effort in providing you with the
most complete

Owner’s Manual

Please read it carefully—especially the instructions,
warnings and cautions. It will help you successfully
install and use your new amplifier. Be sure to read
Sections 3.3.2 and 3.3.3 if you plan to use one of the
amplifier’s two mono modes.

Please send in your warranty registration card today
and save your bill of sale because it is your official
proof of purchase. We hope you enjoy your new ampli­fier, and thank you for choosing Crown.

1.1 Features

Studio Reference

edge technologies that make them the most accurate
reference amplifiers available. For example, in Stereo
mode each channel can actually be treated as a sepa­rate amplifier because of its separate high-voltage
power supplies and ultra-low crosstalk. Here are some
of its many impressive features:

❏ Crown’s unconventional

delivers incredible voltage swings without using
stressful output transistor configurations like other more

amplifiers integrate several cutting

grounded bridge

™

amplifier will

in the business.

™

circuitry

traditional amplifiers. This results in significantly lower
distortion and superior reliability.

❏ Patented

circuitry detects and compensates for overheating and
overload to keep the amplifier working when others
would fail.

®

❏

IOC

(Input/Output Comparator) circuitry immediately
alerts you of any distortion that exceeds 0.05% to
provide dynamic

P.I.P.

❏

❏ Extremely wide dynamic range capable of accurately

❏ Ultra-high damping factor delivers superior loudspeaker

❏ Super-low harmonic and intermodulation distortion give

❏ Two mono modes (Bridge-Mono and Parallel-Mono) for

❏ Custom-designed, tape-wound, low-noise toroidal

❏ High-voltage headroom and high-current headroom

❏ Full protection against shorted outputs, mismatched

❏ Indicators include Enable,

❏ Balanced phone jacks and XLR connectors are pro-

❏ Ground lift switch isolates the AC power and phone jack

❏ Efficient heat sinks and a self-contained, on-demand,

❏ Internal three-position input sensitivity switch provides

❏ Mounts in a standard 19 inch (48.3 cm) equipment rack,

❏ Three year “No-Fault” full warranty completely protects

(Programmable Input Processor) connector
accepts accessories that tailor your amplifier to suit
specific applications.

reproducing 20-bit digital recordings.

motion control for the cleanest, tightest, chest-thumping
bottom end you’ve ever felt—or heard.

your amplifier

driving a wide range of load impedances.

supplies with extremely high power density.

provide energy reserves that make it easy to drive low­impedance loads and highly reactive loads to full power.

loads, general overheating, DC and high-frequency
overloads. Full overvoltage and internal fault protection.

and the Dynamic Range/Level meter.

vided for input. Two pair of 5-way binding posts per
channel are provided for versatile output connection.

audio grounds.

infinitely variable forced-air cooling system prevents
overheating and prolongs component life.

settings of 0.775 volts and 1.4 volts for standard 1 kHz
power, and 26 dB gain.

or units can be stacked directly on top of each other.

your investment and guarantees its specifications.

®

ODEP

(Output Device Emulation Protection)

proof of distortion-free performance

the best transfer function

ODEP, IOC

.

in the business.

, Signal Presence

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A B C D ABCD E F

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Fig. 2.1 Front Facilities

2 Facilities

A. Level Controls

Each channel’s output level can be adjusted accurately
using the 31-position detented level controls on the front
panel (see Section 4.4).

B.

ODEP

Indicators

During normal operation of the amplifier, the
(Output Device Emulation Protection) indicators glow
brightly to show the presence of reserve thermody­namic energy. They dim proportionally as energy
reserves decrease. In the rare event that energy re­serves are depleted, the indicators turn off and
proportionally limits the output drive so the amplifier can
safely continue operating even under severe conditions.
These indicators also help to identify more unusual op­erating conditions (see Figure 4.2).

C.

IOC

Indicators

The

IOC

(Input Output Comparator) indicators serve as

sensitive distortion indicators to provide

distortion-free performance

the indicators remain off. They flash if the output
waveform differs from the input by 0.05% or more (see
Section 4.2). If the input signal level is too high, the
indicators will also flash brightly with a half-second hold
delay to show input overload or output clipping.

. Under normal conditions,

The channel 2 IOC indicator stays on in Parallel-Mono
mode.

See Section 4.2.

D. Signal Presence Indicators

These indicators flash synchronously with the amplifier’s
audio output to show signal presence.

Note: These indi-

ODEP

ODEP

proof of

Note:

cators may not flash at very low input signal levels.

Section 4.2.

See

E. Enable Indicator

This indicator lights when the amplifier has been “en­abled” or turned on, and AC power is available.

F. Enable Switch

This push button is used to turn the amplifier on and off.
When turned on, the output is muted for about four sec­onds to protect your system from start-up transients.
This is why a power sequencer is rarely needed for mul­tiple units. (The turn-on delay can be changed. Contact
Crown’s Technical Support Group for details.)

G. Dust Filter

The dust filter removes large particles from the air drawn
in by the cooling fan. In most cases, the fan will not run
so the filter will remain clean. If the filter becomes dirty, it
can be removed for easy cleaning (see Section 4.5).

H. Dynamic Range / Level Meters

A five-segment output meter is provided for each chan­nel. The meters are factory-set to show dynamic range
of the signals in dB, which is computed as the ratio of
peak to average output power. Also, the meter can op­tionally be set to show output levels (see Section 4.4).

❏ Meter Switches

Two switches behind the front panel can be used to
customize the output meters (H). By default, the meters
display dynamic range. To make the meters display sig­nal levels or to turn them off, see Section 4.4.

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Fig. 2.2 Rear Facilities

I. Reset Switch

This back panel switch can be used to trip and reset the
AC mains circuit breaker (see Section 4.3.4).

J. Power Cord

For 120 VAC, 60 Hz North American units, the

Reference

TT30P plug, and the
12 AWG cord and NEMA 5-15P plug. Other units are
shipped with an appropriate power cord and plug.

K.

P.I.P.

The standard P.I.P.-FX input module is provided with
your amplifier. It provides female XLR input connectors.
Each pair of XLR and phone jack connectors is wired in
parallel so the unused connector can be used as a
“daisy chain” output to connect a source to multiple am­plifiers. Other
P.I.P.-FX to provide additional features that customize
your amplifier for different applications (see Section 8 for
available

I includes a 10 AWG power cord and NEMA

Studio Reference

II includes a

Module

P.I.P.

modules can be used in place of the

P.I.P.

modules).

Studio

L. Balanced XLR Inputs

A balanced three-pin female XLR connector is provided
on the P.I.P.-FX (K) for input to each channel. Caution:

not use the channel 2 input in either mono mode.

Do

N. Stereo / Mono Switch

This switch is used to select one of three operating
modes. Stereo mode is used for normal two-channel
operation, Bridge-Mono mode is used to drive a single
channel with a load impedance of at least 4 ohms, and
Parallel-Mono mode is used to drive a single channel
with a load impedance of less than 4 ohms. WARNING:

Turn off the amplifier before changing this switch
(see Section 3.3).

O. Balanced Phone Jack Inputs

A balanced
each channel. They may be used with either balanced
(tip, ring and sleeve) or unbalanced (tip and sleeve) in­put wiring (see Section 3.3). These inputs are in parallel
with the
inputs if the installed

Do

not use the channel 2 input in either mono mode.

1

¦4-inch phone jack is provided for input to

P.I.P.

connector, so they should not be used as

P.I.P.

has active circuitry. Caution:

P. Ground Lift Switch

The input signal ground may be isolated from the AC
ground with this switch to help prevent unwanted
ground loops. It affects
no affect on the
ing the switch inserts an impedance between the sleeve
of each phone input jack and the circuit ground.

P.I.P.

only the phone jacks (O). It has

module’s XLR connectors. Activat-

M. Output Connectors

Two pairs of versatile 5-way binding posts are provided
for the output of each channel so multiple loudspeakers
can be connected easily. They accept banana plugs,
spade lugs or bare wire.

❑ Input Sensitivity Switch

The three-position input sensitivity switch inside the am­plifier can be accessed by removing the
Settings include 0.775 volts and 1.4 volts for rated out­put, and 26 dB voltage gain (see Section 4.4).

P.I.P.

module.

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3 Installation

3.1 Mounting

Studio Reference

19 inch (48.3 cm) rack mounting or stacking without a
cabinet. In a rack, it is best to mount units directly on
top of each other. This provides the most efficient air
flow and support. If the rack will be transported, we
recommend that you fasten the amplifier’s back panel
securely to the rack to help support the unit’s weight.

Before proceeding, make sure the meter switches are
set to your liking. The front panel assembly must first
be removed to change these switches, so it is easier to
do before the unit is mounted (see Section 4.4).

By now, you may be looking for rack ears. The rack
ears are covered by two attractive end caps which are
held in place by phillips screws (see Figure 3.2). To
use the rack ears, remove the screws and lift off the
caps. With sufficient side clearance, you can reinstall
the end caps once the amplifier is mounted in the rack.

amplifiers are designed for standard

®

FRONT VIEW

19 in

(48.3 cm)

SIDE VIEW

16 in

(40.6 cm)

Fig. 3.1 Mounting Dimensions

(3.6 cm)

1.4 in

7 in
(17.3 cm)

3.2 Cooling

Your amplifier has an internal variable speed fan that is
controlled to match the unit’s real-time cooling needs.
With proper installation and typical studio use, the fan
may never need to run. For best results, you should fa­miliarize yourself with its cooling requirements.

Here are some tips to help keep your amplifier cool.
First, never block the amplifier’s front or side air vents.
If the amplifier is rack-mounted, its sides should be at
least 2 inches (5 cm) away from the cabinet (see Fig­ure 3.3). Also, open rack spaces should be covered to
prevent heated air from the side vents from being
drawn out the front of the rack into the front air intake.

You will know when your
has sufficient cooling because its
be brightly lit. If the amplifier’s
turn off, overly demanding conditions are forcing it to
protect itself from overheating. If you experience a
cooling problem, you should consider several factors
that may be contributing to the problem, including load
impedance, air flow and ambient air temperature.

Low-impedance loads generate more heat than higher
impedance loads. To avoid impedance-related cooling
problems, connect loads to each channel with a total
impedance of at least 2 ohms in Stereo, 4 ohms in
Bridge-Mono, and 1 ohm in Parallel-Mono mode (see
Section 3.3 for wiring instructions). If your loads are
reasonable and you still have a cooling problem, check
for shorts in the loudspeaker cables, and look for prob­lems with air flow or ambient air temperature.

Air flow restrictions are the most common cause of inad­equate cooling. Restrictions may result from improper

IMPORTANT: Be sure the back of

the amplifier is supported.

Studio Reference

ODEP

ODEP

indicators dim or

17 in

amplifier

indicators will

Page 10

6 in

AIR

FLOW

2 in

MIN.

AMPLIFIER

(TOP VIEW)

AIR FLOW

AIR

FLOW

RACK

CABIN

Fig. 3.3 Top View of a Rack-Mounted UnitFig. 3.2 Removing an End Cap

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AIR

FLOW

AIR

FLOW

BLOWER

(OPTION 2)

EQUIPMENT

RACK

(SIDE VIEW)

BLOWER

(OPTION 1)

FRONT

OF

RACK

DOOR

Fig. 3.4 Proper Air Flow with a Rack-Mounted Blower

mounting, piles of power cords, clogged dust filters and
closed rack doors. Mount your amplifier to allow suffi­cient air flow into the front intake, out the side exhaust
vents, and out the back of the rack. An air flow restriction
like a pile of power cords can simply be moved out of the
way. Air filters should be cleaned using the procedure in
Section 4.5. If rack doors are the problem, you can leave
them open, remove them, or install a grille. If you install
a grille, we recommend using a wire grille because per­forated panels restrict air flow by at least 40%.

If your

ODEP

indicators still dim under demanding con­ditions, we recommend that you check the table of
indicator states in Figure 4.2 to eliminate other condi­tions that could be the source of the problem. If it is
clear that the amplifier does not have sufficient air flow,

you may want to install supplemental cooling like a
rack-mounted blower or an air conditioner.

A “squirrel cage” blower can be installed at the bottom
of the rack so it blows outside air into the space be­tween the door and the front of the amplifiers. This will
pressurize the “chimney” behind the door (Figure 3.4,
Option 1). The blower should not blow air into or take
air out of the space behind the amplifiers. For racks
without a front door, you can evacuate the rack by
mounting the blower at the top of the rack so air blows
out the back (Figure 3.4, Option 2). You can estimate a
rack’s required air flow by adding each unit’s maxi­mum air flow rating. The

Studio Reference

I

and II can
each move up to 45 cubic feet (1.3 cubic meters) of air
per minute. So if you put one of each in a rack, you
would need 90 cubic feet (2.5 cubic meters) of air flow
through the rack per minute under worst-case condi­tions (45 cubic feet + 45 cubic feet = 90 cubic feet).

Another way to increase cooling is to use air condition­ing. It is rarely a necessity because internal fans and
rack-mounted blowers almost always provide enough
air flow for the most extreme conditions. Still, air condi­tioning helps reduce the ambient temperature of the air
flowing through the rack. If you plan to use air condi­tioning, refer to Section 7 for information on calculating
the hourly thermal dissipation of your system.

3.3 Wiring

Figures 3.5 through 3.7 show common ways to set up a

Studio Reference

tors are located on the back panel. Be careful when

amplifier. Input and output connec-

MIXER

STUDIO REFERENCE

AMPLIFIER

STEREO

PARALLEL

MONO

CAUTION:

TURN OFF AMPLIFIER

BEFORE CHANGING THIS SWITCH!

STEREO MODE

CHANNEL 1

CHANNEL 2

FX

PUSHPUSH

STUDIO

Reference

BRIDGE

MONO

Fig. 3.5 Stereo Wiring

CH-2 CH-1

CHANNEL 2

LOUDSPEAKER

CHANNEL 1

LOUDSPEAKER

–

+

+

–

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making connections, selecting sources and controlling
output levels. The load you save may be your own!
Crown is not responsible for damaged loads that result
from carelessness or deliberate overpowering.

CAUTION: Always disconnect the AC power and
turn the level controls down when making or break­ing connections. This practice reduces the chance of

loud blasts that can cause loudspeaker damage.

Studio Reference

amplifiers provide three operating
modes: Stereo, Bridge-Mono and Parallel-Mono. Ste­reo mode provides standard two-channel operation;
Bridge-Mono provides a single channel with double
the output voltage of Stereo mode; and Parallel-Mono
mode provides a single channel with double the output
current of Stereo mode. These modes can be selected
using the stereo/mono switch on the back panel. Each
mode is wired differently, so be sure to note any spe­cial wiring requirements for the mode you will be using.

3.3.1 Stereo (Two-Channel) Operation

Stereo mode installation is very intuitive: input chan­nel 1 feeds output channel 1, and input channel 2
feeds output channel 2. To put the amplifier into Stereo

mode, turn it off, slide the stereo/mono switch to the
center position, and properly connect the output wiring
as shown in Figure 3.5. Each output channel has two
sets of binding posts to make it easier for you to con­nect multiple loudspeaker cables to each channel. Be
sure to observe correct loudspeaker polarity (see Fig­ure 3.5) and be careful not to short the outputs.

CAUTION: In Stereo mode, never tie an amplifier’s
outputs together directly, and never parallel them
with the output of another amplifier. Such connec-

tions do not result in increased output power, but may
activate the protection circuitry to prevent overheating.

3.3.2 Bridge-Mono Operation

Bridge-Mono mode is used to drive loads with a total
impedance of at least 4 ohms (see Parallel-Mono if the
load is less than 4 ohms). Wiring for Bridge-Mono
mode is different from the other modes and requires
special attention. First, turn off the amplifier. Then se­lect Bridge-Mono mode by sliding the stereo/mono
switch to the right (as you face the back panel). Both
outputs receive the channel 1 input signal, but chan­nel 2 is inverted so it can be bridged with channel 1.
Do not use the channel 2 input or signal quality will be

Page 12

MIXER

STUDIO REFERENCE

AMPLIFIER

STEREO

PARALLEL

MONO

CAUTION: TURN OFF AMPLIFIER

BEFORE CHANGING THIS SWITCH!

BRIDGE-MONO MODE

CHANNEL 1

DO NOT USE

THE CHANNEL 2

INPUTS.

FX

PUSHPUSH

STUDIO

Reference

BRIDGE

MONO

Fig. 3.6 Bridge-Mono Wiring

CH-2 CH-1

–

+

LOUDSPEAKER

DO NOT USE

THE BLACK

BINDING

POSTS.

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greatly degraded. Also, turn down the channel 2 level
control (fully counterclockwise).

Note: The channel 2 input and level control are not de­feated in Bridge-Mono mode. Any signal feeding chan­nel 2 will work against the channel 1 signal, and usually
results in distortion and inefficient operation.

Connect the load across the two red (+) binding posts
(see Figure 3.6). The positive (+) loudspeaker lead
connects to the red channel 1 binding post, and the
negative (–) or ground lead from the loudspeaker con­nects to the red channel 2 binding post. Do not con­nect the black binding posts (–). Also, the load must be
balanced (neither side shorted to ground).

CAUTION: Only connect balanced equipment
(meters, switches, etc.) to the Bridge-Mono output.
Both sides of the line must be isolated from the in­put grounds or oscillations may occur.

3.3.3 Parallel-Mono Operation

Parallel-Mono mode is used to drive loads with a total
impedance of less than 4 ohms (see Bridge-Mono if the
load is 4 ohms or more). Wiring for Parallel-Mono mode

is very different from the other modes and requires
special attention.

To select Parallel-Mono mode, turn off the amplifier and
slide the stereo/mono switch to the left (as you face the
back panel). Connect the input signal to channel 1 only.
The channel 2 input and level control are bypassed in
this mode, so they should not be used.

Note: It is normal for the channel 2 IOC indicator to stay
on in Parallel-Mono mode.

Connect the load to the channel 1 output as shown in
Figure 3.7. The positive (+) lead from the loudspeaker
connects to the red channel 1 binding post, and the
negative (–) or ground lead from the loudspeaker con­nects to the black channel 1 binding post. Finally, in­stall a jumper wire of at least 14 gauge between the
channel 1 and channel 2 red binding posts.

CAUTION: When Parallel-Mono wiring is installed,
do not attempt to operate in Stereo or Bridge-Mono
mode until the wiring is removed (especially the
jumper wire). Failure to do so will result in high dis­tortion and excessive heating.

MIXER

STUDIO REFERENCE

AMPLIFIER

STEREO

PARALLEL

MONO

CAUTION: TURN OFF AMPLIFIER

BEFORE CHANGING THIS SWITCH!

PARALLEL-MONO MODE

CHANNEL 1

ADD A 14 GAUGE

OR LARGER

JUMPER BETWEEN

PUSHPUSH

THE CHANNEL 1

AND 2 RED (+)

BINDING POSTS

THE CHANNEL 2

INPUTS ARE

NOT USED

FX

STUDIO

Reference

BRIDGE

MONO

Fig. 3.7 Parallel-Mono Wiring

–

+

LOUDSPEAKER

CH-2 CH-1

Page 13