®
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: 219-294-8000
Printed on
recycled paper.
™
™
™
™
™
Trademark Notice: Studio Reference, Smart Amp, MPX-6, SMX-6, AMB-5, and grounded bridge™
K80604-0
8/95
are trademarks and Crown, IOC®, ODEP,® IQ System® and P.I.P.® are registered trademarks of
®
Crown International, Inc. Other trademarks are the property of their respective owners.
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: 800-342-6939 (U.S.A.) or 219-294-8200 Fax: 219-294-8301
IMPORTANT
STUDIO REFERENCE AMPLIFIERS
REQUIRE CLASS 1 OUTPUT WIRING.
A V I S
C A U T I O N
RISQUE DE CHOC ÉLECTRIQUE
N’OUVREZ PAS
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.
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! Donotlocatesensitivehigh-gainequip-
ment 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.
WARNING
TO REDUCE THE RISK OF ELECTRIC
SHOCK, DO NOT EXPOSE THIS
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.
EQUIPMENT TO RAIN OR MOISTURE!
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.
Studio Reference
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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 ........................................................... 21
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
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ILLUSTRATIONS
1.1 Studio Reference I Amplifier ........................................... 6
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 Indicator States.................................. 20
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 I Minimum Power Matrix .................... 29
6.2 Studio Reference II Minimum Power Matrix .................. 30
6.3 Studio Reference I Maximum Power Matrix ................... 31
6.4 Studio Reference II Maximum Power Matrix ................. 32
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 I Power Draw, Current Draw and
Thermal Dissipation at Various Duty Cycles ................... 36
7.2 Studio Reference II Power Draw, Current Draw and
Thermal Dissipation at Various Duty Cycles ................... 37
8.1 Installing a 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 com-
pany immediately. Only you, the consignee, may ini-
tiate a claim for shipping damage. Crown will be
happy to cooperate fully as needed. Save the ship-
ping 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
traditional amplifiers. This results in significantly lower
distortion and superior reliability.
❏ Patented ODEP® (Output Device Emulation Protection)
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 proof of distortion-free performance.
The stunning realism you will experience when listen-
ing to a Crown Studio Reference™ amplifier will
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 leader-
ship and technical excellence for which Crown has
long been known.
❏ P.I.P. (Programmable Input Processor) connector
accepts accessories that tailor your amplifier to suit
specific applications.
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 low-
frequency transient response is the standard by which
all others must be judged.
❏ Extremely wide dynamic range capable of accurately
reproducing 20-bit digital recordings.
❏ Ultra-high damping factor delivers superior loudspeaker
motion control for the cleanest, tightest, chest-thumping
bottom end you’ve ever felt—or heard.
❏ Super-low harmonic and intermodulation distortion give
your amplifier the best transfer function in the business.
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 in the business.
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.
❏ Two mono modes (Bridge-Mono and Parallel-Mono) for
driving a wide range of load impedances.
❏ Custom-designed, tape-wound, low-noise toroidal
supplies with extremely high power density.
❏ High-voltage headroom and high-current headroom
provide energy reserves that make it easy to drive low-
impedance loads and highly reactive loads to full power.
❏ Full protection against shorted outputs, mismatched
loads, general overheating, DC and high-frequency
overloads. Full overvoltage and internal fault protection.
❏ Indicators include Enable, ODEP, IOC, Signal Presence
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 ampli-
fier, and thank you for choosing Crown.
and the Dynamic Range/Level meter.
❏ Balanced phone jacks and XLR connectors are pro-
vided for input. Two pair of 5-way binding posts per
channel are provided for versatile output connection.
❏ Ground lift switch isolates the AC power and phone jack
1.1 Features
audio grounds.
Studio Reference amplifiers integrate several cutting
edge technologies that make them the most accurate
reference amplifiers available. For example, in Stereo
mode each channel can actually be treated as a sepa-
rate amplifier because of its separate high-voltage
power supplies and ultra-low crosstalk. Here are some
of its many impressive features:
❏ Efficient heat sinks and a self-contained, on-demand,
infinitely variable forced-air cooling system prevents
overheating and prolongs component life.
❏ Internal three-position input sensitivity switch provides
settings of 0.775 volts and 1.4 volts for standard 1 kHz
power, and 26 dB gain.
❏ Mounts in a standard 19 inch (48.3 cm) equipment rack,
or units can be stacked directly on top of each other.
❏ Crown’s unconventional grounded bridge™ circuitry
delivers incredible voltage swings without using
stressful output transistor configurations like other more
❏ Three year “No-Fault” full warranty completely protects
your investment and guarantees its specifications.
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A
B C D
D C B
A
E
F
®
G
Fig. 2.1 Front Facilities
H
2 Facilities
cators may not flash at very low input signal levels. See
Section 4.2.
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).
E. Enable Indicator
This indicator lights when the amplifier has been “en-
abled” or turned on, and AC power is available.
B. ODEP Indicators
During normal operation of the amplifier, the ODEP
(Output Device Emulation Protection) indicators glow
brightly to show the presence of reserve thermody-
namic energy. They dim proportionally as energy
reserves decrease. In the rare event that energy re-
serves are depleted, the indicators turn off and ODEP
proportionally limits the output drive so the amplifier can
safely continue operating even under severe conditions.
These indicators also help to identify more unusual op-
erating conditions (see Figure 4.2).
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 sec-
onds to protect your system from start-up transients.
This is why a power sequencer is rarely needed for mul-
tiple 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).
C. IOC Indicators
The IOC (Input Output Comparator) indicators serve as
sensitive distortion indicators to provide proof of
distortion-free performance. Under normal conditions,
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. Note:
The channel 2 IOC indicator stays on in Parallel-Mono
mode. See Section 4.2.
H. Dynamic Range / Level Meters
A five-segment output meter is provided for each chan-
nel. 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 op-
tionally 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 sig-
nal levels or to turn them off, see Section 4.4.
D. Signal Presence Indicators
These indicators flash synchronously with the amplifier’s
audio output to show signal presence. Note: These indi-
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Fig. 2.2 Rear Facilities
N. Stereo/ Mono Switch
I. Reset 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).
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 Studio
Reference I includes a 10 AWG power cord and NEMA
TT30P plug, and the Studio Reference II includes a
12 AWG cord and NEMA 5-15P plug. Other units are
shipped with an appropriate power cord and plug.
O. Balanced Phone Jack Inputs
A balanced 1¦4-inch phone jack is provided for input to
each channel. They may be used with either balanced
(tip, ring and sleeve) or unbalanced (tip and sleeve) in-
put wiring (see Section 3.3). These inputs are in parallel
with the P.I.P. connector, so they should not be used as
inputs if the installed P.I.P. has active circuitry. Caution:
Do not use the channel 2 input in either mono mode.
K. P.I.P. Module
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 am-
plifiers. Other P.I.P. modules can be used in place of the
P.I.P.-FX to provide additional features that customize
your amplifier for different applications (see Section 8 for
available P.I.P. modules).
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 only the phone jacks (O). It has
no affect on the P.I.P. module’s XLR connectors. Activat-
ing the switch inserts an impedance between the sleeve
of each phone input jack and the circuit ground.
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:
Do not use the channel 2 input in either mono mode.
M. Output Connectors
❑ Input Sensitivity Switch
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.
The three-position input sensitivity switch inside the am-
plifier can be accessed by removing the P.I.P. module.
Settings include 0.775 volts and 1.4 volts for rated out-
put, and 26 dB voltage gain (see Section 4.4).
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3.2 Cooling
3 Installation
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 fa-
miliarize yourself with its cooling requirements.
3.1 Mounting
Studio Reference amplifiers are designed for standard
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.
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 Fig-
ure 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.
®
7 in
FRONT VIEW
(17.3 cm)
You will know when your Studio Reference amplifier
has sufficient cooling because its ODEP indicators will
be brightly lit. If the amplifier’s ODEP indicators dim or
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.
19 in
(48.3 cm)
SIDE VIEW
16 in
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 prob-
lems with air flow or ambient air temperature.
1.4 in
(3.6 cm)
(40.6 cm)
Fig. 3.1 Mounting Dimensions
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).
Airflowrestrictionsarethemostcommoncauseofinad-
equate cooling. Restrictions may result from improper
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.
17 in
IMPORTANT: Be sure the back of
the amplifier is supported.
AIR
FLOW
AIR
FLOW
6 in
AMPLIFIER
(TOP VIEW)
2 in
MIN.
RACK
CABINE
AIR FLOW
Fig. 3.2 Removing an End Cap
Fig. 3.3 Top View of a Rack-Mounted Unit
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FRONT
you may want to install supplemental cooling like a
rack-mounted blower or an air conditioner.
AIR
FLOW
BLOWER
OF
(OPTION 2)
RACK
DOOR
A “squirrel cage” blower can be installed at the bottom
of the rack so it blows outside air into the space be-
tween 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 maxi-
mum 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 condi-
tions (45 cubic feet + 45 cubic feet = 90 cubic feet).
EQUIPMENT
RACK
(SIDE VIEW)
AIR
FLOW
BLOWER
(OPTION 1)
Fig. 3.4 Proper Air Flow with a Rack-Mounted Blower
mounting, pilesofpowercords, cloggeddustfiltersand
closed rack doors. Mount your amplifier to allow suffi-
cient air flow into the front intake, out the side exhaust
vents, andoutthebackoftherack. Anairflowrestriction
likeapileofpowercordscansimplybemovedoutofthe
way. Airfiltersshouldbecleanedusingtheprocedurein
Section 4.5.Ifrackdoorsaretheproblem,youcanleave
them open, remove them, or install a grille. If you install
a grille, we recommend using a wire grille because per-
forated panels restrict air flow by at least 40%.
Another way to increase cooling is to use air condition-
ing. 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 condi-
tioning helps reduce the ambient temperature of the air
flowing through the rack. If you plan to use air condi-
tioning, refer to Section 7 for information on calculating
the hourly thermal dissipation of your system.
If your ODEP indicators still dim under demanding con-
ditions, we recommend that you check the table of
indicator states in Figure 4.2 to eliminate other condi-
tions that could be the source of the problem. If it is
clear that the amplifier does not have sufficient air flow,
3.3 Wiring
Figures 3.5 through 3.7 show common ways to set up a
Studio Reference amplifier. Input and output connec-
tors are located on the back panel. Be careful when
STEREO MODE
CHANNEL 2
LOUDSPEAKER
–
+
CHANNEL 1
CHANNEL 1
LOUDSPEAKER
+
–
CHANNEL 2
MIXER
CH-2
CH-1
FX
P U S H
P U S H
S
T
U
D
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Reference
STUDIO REFERENCE
AMPLIFIER
STEREO
PARALLEL
MONO
BRIDGE
MONO
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH!
Fig. 3.5 Stereo Wiring
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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.
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 con-
nect multiple loudspeaker cables to each channel. Be
sure to observe correct loudspeaker polarity (see Fig-
ure 3.5) and be careful not to short the outputs.
CAUTION: Always disconnect the AC power and
turn the level controls down when making or break-
ing connections. This practice reduces the chance of
loud blasts that can cause loudspeaker damage.
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.
Studio Reference amplifiers provide three operating
modes: Stereo, Bridge-Mono and Parallel-Mono. Ste-
reo 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 spe-
cial wiring requirements for the mode you will be using.
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 se-
lect 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 chan-
nel 2 is inverted so it can be bridged with channel 1.
Do not use the channel 2 input or signal quality will be
3.3.1 Stereo (Two-Channel) Operation
Stereo mode installation is very intuitive: input chan-
nel 1 feeds output channel 1, and input channel 2
feeds output channel 2. To put the amplifier into Stereo
BRIDGE-MONO MODE
–
+
CHANNEL 1
LOUDSPEAKER
MIXER
DO NOT USE
THE CHANNEL 2
INPUTS.
CH-2
CH-1
FX
DO NOT USE
THE BLACK
BINDING
P U S H
P U S H
POSTS.
S
T
U
D
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O
Reference
STUDIO REFERENCE
AMPLIFIER
STEREO
PARALLEL
MONO
BRIDGE
MONO
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH!
Fig. 3.6 Bridge-Mono Wiring
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greatly degraded. Also, turn down the channel 2 level
control (fully counterclockwise).
is very different from the other modes and requires
special attention.
Note: The channel 2 input and level control are not de-
feated in Bridge-Mono mode. Any signal feeding chan-
nel 2 will work against the channel 1 signal, and usually
results in distortion and inefficient operation.
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.
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 con-
nects to the red channel 2 binding post. Do not con-
nect the black binding posts (–). Also, the load must be
balanced (neither side shorted to ground).
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 con-
nects to the black channel 1 binding post. Finally, in-
stall a jumper wire of at least 14 gauge between the
channel 1 and channel 2 red binding posts.
CAUTION: Only connect balanced equipment
(meters, switches, etc.) to the Bridge-Mono output.
Both sides of the line must be isolated from the in-
put grounds or oscillations may occur.
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 dis-
tortion and excessive heating.
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
PARALLEL-MONO MODE
–
+
CHANNEL 1
ADD A 14 GAUGE
OR LARGER
JUMPER BETWEEN
THE CHANNEL 1
AND 2 RED (+)
LOUDSPEAKER
MIXER
THE CHANNEL 2
INPUTS ARE
NOT USED
BINDING POSTS
CH-2
CH-1
FX
P U S H
P U S H
S
T
U
D
I
O
Reference
STUDIO REFERENCE
AMPLIFIER
STEREO
PARALLEL
MONO
BRIDGE
MONO
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH!
Fig. 3.7 Parallel-Mono Wiring
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