Crown Micro-Tech 600 User manual

ODEP
CH1 CH2
POWER
OFF
ODEP
CH1 CH2
POWER
OFF
Models:
Micro-Tech 600, 1200 & 2400
Micro-Tech 601, 1201 & 2401
Some models may be exported under the name Amcron .®
102990-1
7/97
©1997byCrownInternational,Inc.,P.O.Box1000,Elkhart,IN46515-1000U.S.A.Telephone:[phone].
Fax: [phone]. Micro-Tech amplifiers are produced by the Professional Audio Division of Crown
International, Inc. Trademark Notice: Grounded bridge
™is a trademark and
Amcron ,
®
Crown ,
®
Techron ,
®
Micro-Tech ,
®
ODEP
®and
TEF
®areregisteredtrademarksofCrownInternational,Inc.Othertrademarksare
the property of their respective owners.
®
®
Commercial
Audio
LL 32521C
(MT-600 & 1200)
120 VAC North
American
Units Only:
Commercial
Audio
E106377
(MT-600 & 1200)
Approved for
THX Theatre
Systems
(MT-600 & 1200)
®
For
Canada
(MT-2400)

WORLDWIDE
SUMMARY OF WARRANTY
The Crown Audio Division of Crown International, Inc., 1718 West
Mishawaka Road, Elkhart, Indiana 46517-4095 U.S.A. warrants to you,
theORIGINALPURCHASERandANYSUBSEQUENTOWNERofeach
NEW Crown1product, 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.
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
whichoccurredwithin the Warranty Period. Itdoesnot 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.
WHAT THE WARRANTOR WILL DO
We will remedy any defect, regardless of the reason for failure (except
asexcluded),byrepair,replacement, or refund. We may not elect refund
unless you agree, or unless we are unable to provide replacement, and
repairisnotpracticalorcannotbetimelymade.Ifarefundiselected,then
you must make the defective or malfunctioning product available to us
freeandclearofallliensor otherencumbrances. Therefundwillbeequal
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.
HOW TO OBTAIN WARRANTY SERVICE
You must notify us of your need for warranty service not later than ninety
(90)daysafter expirationofthe warranty period.Allcomponents 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 DAMAGES
YOUARENOTENTITLEDTORECOVERFROMUSANYINCIDENTAL
DAMAGES RESULTING FROM ANY DEFECT IN THE NEW CROWN
PRODUCT.THISINCLUDESANYDAMAGETOANOTHERPRODUCT
OR PRODUCTS RESULTING FROM SUCH A DEFECT.
WARRANTY ALTERATIONS
No person has the authority to enlarge, amend, or modify this Crown
Warranty. This Crown Warranty is not extended by the length of time
whichyouaredeprivedof theuseofthenew Crownproduct.Repairsand
replacementparts provided underthe terms ofthis Crown Warrantyshall
carry only the unexpired portion of this Crown Warranty.
DESIGN CHANGES
Wereservetherighttochangethedesignofanyproductfromtimetotime
without notice and with no obligation to make corresponding changes in
products previously manufactured.
LEGAL REMEDIES OF PURCHASER
Noactionto enforce this CrownWarrantyshall be commenced laterthan
ninety (90) days after expiration of the warranty period.
THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERS
CONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.
9/90
NORTH AMERICA
SUMMARY OF WARRANTY
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 prod-
uct, for a period of three (3) years from the date of purchase by the original
purchaser(the “warranty period”)thatthe newCrownproduct isfreeof defects
in materials and workmanship. We further warrant the new Crown product
regardless of the reason for failure, except as excluded 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.
WHAT THE WARRANTOR WILL DO
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
thedefective ormalfunctioning productavailable tous freeandclearofallliens
or other encumbrances. The refund will be equal to the actual purchase price,
notincludinginterest,insurance, closing costs, and other finance chargesless
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.)
HOW TO OBTAIN WARRANTY SERVICE
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.
WARRANTY ALTERATIONS
Nopersonhastheauthority toenlarge,amend,ormodify thisCrownWarranty.
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
providedunder theterms ofthis CrownWarranty shallcarry onlythe unexpired
portion of this Crown Warranty.
DESIGN CHANGES
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.
LEGAL REMEDIES OF PURCHASER
THIS CROWN WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, YOU
MAYALSOHAVEOTHERRIGHTSWHICHVARYFROMSTATETOSTATE.
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.
9/90
Telephone: [phone]. Facsimile: 219-294-8301
Telephone: [phone]. Facsimile: 219-294-8301
THREE YEAR
FULL WARRANTY
YEAR
3
YEAR
3

Printed on
recycled paper.
WATCH FOR THESE SYMBOLS:
Thelightningbolt
triangle is used to
alert the user to the
risk of electric shock.
Theexclamationpoint
triangle is used to alert the
user to important operating or
maintenanceinstructions.
WARNING
TO REDUCE THE RISK OF ELECTRIC
SHOCK, DO NOT EXPOSE THIS
EQUIPMENT TO RAIN OR MOISTURE!
Magnetic Field
CAUTION! Donotlocatesensitivehigh-gainequip-
ment such as preamplifiers or tape decks directly
above or below the unit. Because this amplifierhas
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.
Ifanequipmentrackisused,werecommendlocating
the amplifier(s) in the bottom of the rack and the
preamplifier or other sensitive equipment at the top.
IMPORTANT
THE MICRO-TECH 2400 REQUIRES CLASS 1
OUTPUT WIRING. THE MICRO-TECH 600 &
1200 REQUIRE CLASS 2 OUTPUT WIRING.
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 main-
tenance. 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
Plant 2 SW, 1718 W. Mishawaka Rd., Elkhart, Indiana 46517 U.S.A.
Phone: [phone] (North America, Puerto Rico and Virgin Islands) or 219-294-8200
Fax: [phone] Fax Back (North America only): 800-294-4094 or 219-293-9200
Fax Back (International): 219-294-8100 Internet: http://www.crownintl.com
C A U T I O N
RISK OF ELECTRIC SHOCK
DO NOT OPEN
TO PREVENT ELECTRIC SHOCK DO
NOT REMOVETOP OR BOTTOM
COVERS. NO USER SERVICEABLE
PARTS INSIDE. REFER SERVICING
TO QUALIFIED SERVICE PERSON-
NEL. DISCONNECT POWER CORD
BEFORE REMOVING BACK PANEL
COVERTO ACCESS GAIN SWITCH.
A V I S
RISQUE DE CHOC ÉLECTRIQUE
N’OUVREZ PAS
À PRÉVENIR LE CHOC ÉLECTRIQUE
N’ENLEVEZ PAS LES COUVERCLES. IL
N’Y A PAS DES PARTIES SERVICEABLE
À L’INTÉRIEUR.TOUS REPARATIONS
DOIT ETRE FAIRE PAR PERSONNEL
QUALIFIÉ SEULMENT. DÉBRANCHER
LA BORNE AVANT D’ENLEVER LA
COVERTURE EN ARRIÈRE.

Page 4
Micro-Tech 600/1200/2400 Power Amplifiers
CONTENTS
1 Welcome .......................................................................... 7
1.1 Unpacking ................................................................. 7
1.2 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.................... 11
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 Requirements................................ 18
4 Operation ....................................................................... 19
4.1 Precautions.............................................................. 19
4.2 Indicators................................................................. 19
4.3 Protection Systems .................................................. 19
4.3.1 ODEP ............................................................ 19
4.3.2 Ultrasonic and Radio Frequency Protection... 20
4.3.3 Drive Protection............................................. 20
4.3.4 Transformer Thermal Protection..................... 20
4.3.5 Fuses and Circuit Breakers ........................... 20
4.4 Controls ................................................................... 21
4.5 Filter Cleaning.......................................................... 21
5 Technical Information................................................... 22
5.1 Overview ................................................................. 22
5.2 Circuit Theory .......................................................... 22
5.2.1 Stereo Operation ........................................... 22
5.2.2 Bridge-Mono Operation................................. 24
5.2.3 Parallel-Mono Operation................................ 24
6 Specifications ............................................................... 25
7 AC Power Draw and Thermal Dissipation................... 34
8 Accessories................................................................... 36
8.1 Cooling Fan Options ................................................ 36
8.2 Input Connectors ..................................................... 36
8.2.1 MT-XLR.......................................................... 36
8.2.2 MT-BB ........................................................... 36
9 Service ........................................................................... 37
9.1 Worldwide Service ................................................... 37
9.2 North American Service ........................................... 37
9.2.1 Service at a North American Service Center.. 37
9.2.2 Factory Service ............................................. 37

Page 5
Micro-Tech 600/1200/2400 Power Amplifiers
ILLUSTRATIONS
1.1 Micro-Tech Amplifier .................................................................. 7
2.1 Front Facilities ............................................................................ 8
2.2 Rear Facilities ............................................................................ 9
3.1 Mounting Dimensions .............................................................. 10
3.2 Top View of a Rack-Mounted Unit............................................. 10
3.3 Proper Air Flow with a Rack-Mounted Blower ........................... 10
3.4 Stereo Wiring ........................................................................... 11
3.5 Bridge-Mono Wiring ................................................................. 12
3.6 Parallel-Mono Wiring ................................................................ 13
3.7 Unbalanced Input Wiring for the Optional MT-XLR ................... 14
3.8 Balanced Input Wiring for the Optional MT-XLR........................ 14
3.9 Balanced and Unbalanced Phone Plug Wiring......................... 14
3.10 Subsonic Filter Capacitors ....................................................... 15
3.11 Unbalanced RF Filters.............................................................. 15
3.12 Balanced RF Filters .................................................................. 15
3.13 Wire Size Nomograph .............................................................. 16
3.14 Low-Frequency Protection Circuit for Inductive Loads ............. 17
3.15 Loudspeaker Fuse Nomograph ............................................... 18
3.16 AC Mains Cords and Plugs ...................................................... 18
4.1 Indicators................................................................................. 19
4.2 Input Sensitivity and Ground Lift Switches................................ 21
5.1 Circuit Block Diagram .............................................................. 23
6.1 Micro-Tech 600 Minimum Power Matrix .................................... 27
6.2 Micro-Tech 1200 Minimum Power Matrix .................................. 28
6.3 Micro-Tech 2400 Minimum Power Matrix .................................. 28
6.4 Micro-Tech 600 Maximum Power Matrix ................................... 29
6.5 Micro-Tech 1200 Maximum Power Matrix ................................. 30
6.6 Micro-Tech 2400 Maximum Power Matrix ................................. 30
6.7 Typical Frequency Response ................................................... 31
6.8 Typical Damping Factor ........................................................... 31
6.9 Typical Output Impedance....................................................... 31
6.10 Typical Phase Response .......................................................... 32
6.11 Typical Crosstalk for the Micro-Tech 600 .................................. 32
6.12 Typical Crosstalk for the Micro-Tech 1200 ................................ 33
6.13 Typical Crosstalk for the Micro-Tech 2400 ................................ 33
7.1 Micro-Tech 600 Power Draw, Current Draw and Thermal
Dissipation at Various Duty Cycles ........................................... 34
7.2 Micro-Tech 1200 Power Draw, Current Draw and Thermal
Dissipation at Various Duty Cycles ........................................... 35
7.3 Micro-Tech 2400 Power Draw, Current Draw and Thermal
Dissipation at Various Duty Cycles ........................................... 35
8.1 MT-XLR .................................................................................... 36
8.2 MT-BB ...................................................................................... 36

Page 6
Micro-Tech 600/1200/2400 Power Amplifiers

Page 7
Micro-Tech 600/1200/2400 Power Amplifiers
1 Welcome
Congratulations on your purchase of a Micro-Tech
®
professional power amplifier. Crown’s Micro-Tech 600 ,
1200 and 2400 are the original industry standards for
touring amplifiers. Micro-Tech amplifiers are known
around the world as a the benchmark for high-density,
ultra-pure power in a compact, lightweight package.
In addition, each model gives you Crown’s legendary
ODEP
®protection to keep the show going long after
other amplifiers would fail.
This manual will help you successfully install and use
your new amplifier—we strongly recommend you read
all instructions, warnings and cautions. Be sure to read
Sections 3.3.2 and 3.3.3 if you plan to use the amplifier
in one of its two mono modes. Also for your protection,
please send in your warranty registration card today
and save your bill of sale since it is your official proof
of purchase.
1.1 Unpacking
Please unpack and inspect your new amplifier for any
damage that may have occurred during transit. If dam-
age is found, notify the transportation company imme-
diately. Only you, the consignee, may initiate a claim
for shipping damage. Crown will be happy to cooper-
ate fully as needed. Save the shipping carton as evi-
dence 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
everneedtotransporttheunit.NEVER SHIPTHEUNIT
WITHOUTTHE FACTORY PACK.
1.2 Features
Micro-Tech amplifiers use the latest technology and
miniaturized design to deliver the highest power and
value for their size, weight and price. Crown’s patented
ODEP protection circuitry and grounded bridge
™out-
put stages combine to provide performance and reli-
ability that surpass all traditional designs. Micro-Tech
amplifiers also have an independent high-voltage
power supply for each channel. This approach results
in extremely low crosstalk and makes it possible to use
each channel as a separate amplifier. Here are some
more impressive features of your Micro-Tech amplifier:
❏Patented ODEP (Output Device Emulation Protection)
circuitry compensates for overheating and overload to
keep the amplifier working long after others would fail.
❏Crown’s grounded bridge design delivers incredible
voltage swings without using stressful output transistor
configurations like more traditional amplifiers. This
results in significantly lower distortion and superior
reliability.
❏Very low harmonic and intermodulation distortion result
in the best dynamic transfer function in the industry.
❏High damping factor provides superior motion control
over low-frequency drivers for clean, accurate low end.
❏Two mono modes (Bridge-Mono and Parallel-Mono) for
driving a wide range of load impedances.
❏Full protection against shorted outputs, open circuits,
DC, mismatched loads, general overheating, high-
frequency overloads and internal faults.
❏Efficient heat sinks and self-contained forced air cooling
prevent overheating and prolong component life.
❏Ground lift switch to isolate chassis and phone jack
audio grounds.
❏Binding post outputs provide easy and versatile output
connection.
❏Internal three-position input sensitivity switch provides
settings of 0.775 and 1.4 volts for standard 1 kHz power,
and 26 dB voltage gain.
❏Mounts in a standard 19 inch (48.3 cm) equipment rack
(units can also be stacked).
❏Three year “No-Fault” full warranty completely protects
your investment and guarantees its specifications.
ODEP
CH1 CH2
POWER
OFF
Fig. 1.1 Micro-Tech Amplifier

Page 8
Micro-Tech 600/1200/2400 Power Amplifiers
Fig. 2.1 Front Facilities
ODEP
CH1 CH2
POWER
OFF
AB CC D
2 Facilities
A. Filter Grille
This metal grille supports and protects the dust
filter (B). To clean the dust filter, detach the grille by
removing the three screws that hold it in place.
B. Dust Filter
The dust filter removes large particles from the air
drawn by the cooling fan. Check the filter regularly to
prevent clogging (see Sections 3.2 and 4.5).
C. ODEP Indicators
During normal operation of the Output Device Emula-
tion Protection circuitry, these amber indicators glow
brightly to show that reserve thermodynamic energy is
present. They dim proportionally as energy reserves
decrease. In the rare event that energy reserves are
depleted, the ODEP indicators turn off and the protec-
tion circuitry proportionally limits output drive so the
amplifier can safely continue operating even under
severe conditions. These indicators also help identify
more unusual operating conditions (see Section 4.2).
D. Enable Indicator
This indicator lights when the amplifier is turned on, AC
power is available and the low-voltage power supply
and fan are operational (see Section 4.2).
E. Power Switch
This rocker switch is used to turn the amplifier on and
off. When turned on, the output is muted for approxi-
mately four seconds to protect your system from start-
up transients. (To change the start-up delay time,
contact Crown’s Technical Support Group.)
F. Power Cord
All units are shipped with an appropriate plug and cord
for the required AC voltage (see Figure 3.16). Also, re-
fer to Section 7 for power usage information.
G. Stereo/Mono Switch
The amplifier’s three operating modes are controlled
by this switch. Use Stereo mode for normal two-chan-
nel operation, Bridge-Mono mode to drive a single
channel with a load impedance of at least 4 ohms, and
Parallel-Mono mode to drive a single channel with a
load impedance less than 4 ohms. Important:Turn off
the amplifier before changing the stereo/mono
switch (see Section 3.3).
H. Reset Switches ( Micro-Tech 2400 only)
The Micro-Tech 2400 has two push-button reset
switches on the back panel that are used to reset the
circuit breakers for the high-voltage power supplies.

Page 9
Micro-Tech 600/1200/2400 Power Amplifiers
Fig. 2.2 Rear Facilities
CAUTION:
THIS COVER IS NECESSARY FOR
EFFICIENT COOLING OF THE AMPLIFIER.
REMOVE ONLY TO ACCESS GAIN SWITCH.
0
1
2
3456789
10
11
12
0
1
2
3456789
10
11
12
BRIDGE-MONO WIRING
TURN AMPLIFIER OFF.
SET STEREO/MONO
SWITCH TO
BRIDGE-MONO.
OUTPUT ACROSS
RED TERMINALS
ONLY. (CH-1
IS POSITIVE.)
PARALLEL-MONO WIRING
TURN AMPLIFIER OFF.
SET STEREO/MONO
SWITCH TO
PARALLEL-MONO.
ADD JUMPER (14
GAGE OR LARGER)
ACROSS RED
TERMINALS.
OUTPUT ACROSS CH-1
TERMINALS ONLY.
1
2
3
4
1
2
3
CH-2 CH-1
+
–
–
+
INPUT GROUND LIFT
(AFFECTS PHONE INPUTS ONLY.)
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH!
STEREO
BRIDGE
MONO
PARALLEL
MONO
CLASS 1
OUTPUT
WIRING
REQUIRED.
WARNING: TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE.
OUTPUTS
LIFT
REG. U.S. PAT. OFF.
4,330,809
4,611,180
MODEL: MICRO-TECH 2400 SERIES
AC VOLTS: 120 AMPS: 17 60 Hz
MAXIMUM OUTPUT: 900 WATTS
PER CHANNEL INTO 2 OHMS AT 1 KHz
WITH NO MORE THAN 0.1% THD.
UNBALANCED
INPUT WIRING
BALANCED
INPUT WIRING
+
–
TIP
RING
SLEEVE
GND
+
TIP
SLEEVE
GND
CH-2
(MONO)
INPUT
GAIN
CH-1
INPUT GAIN
THIS AMPLIFIER IS EQUIPPED WITH SELECTABLE INPUT SENSITIVITY. REMOVE COVER PLATE (ABOVE) TO ACCESS SENSITIVITY SWITCH.
®
INTERNATIONAL, INC.
ELECTRONIC EQUIPMENT
ELKHART, IN 46517
MADE IN U.S.A.
SERIAL NUMBER
0000
000000
FGHI K KL MMJJ
PUSH TO RESET
I. Cover Plate
This cover plate is removed when changing the
amplifier’s input sensitivity (see Section 4.4) or install-
ing an MT-XLR or MT-BB accessory (see Section 8.2).
❑ Input Sensitivity Switch
The three-position input sensitivity switch is located in-
side the amplifier behind the cover plate (I). Settings
include 0.775 volts and 1.4 volts for standard 1 kHz
power, and 26 dB gain (see Section 4.4).
J. Level Controls
These back panel level controls are used to set the
amplifier’s output levels (see Section 4.4). Be sure to
turn down the channel 2 level control (fully counter-
clockwise) when operating in Bridge-Mono mode.
K. Balanced Phone Jack Inputs
A balanced ¼-inch phone jack input is provided for
each channel. They may be wired for balanced (tip,
ring and sleeve) or unbalanced (tip and sleeve) opera-
tion (refer to Section 3.3.4). XLR and barrier block in-
put connectors are available with the MT-XLR and
MT-BB accessories(see Section8.2). Caution: Do not
use the channel 2 input in either mono mode.
L. Ground Lift Switch
This switch is used to isolate the phone jack signal
grounds from the AC power (chassis) ground. Moving
the switch to the “lift” position helps prevent the hum
associated with ground loops (see Section 4.4).
M. Output Jacks
A pair of versatile binding posts is provided for output
connection to each channel. Loudspeakers can be
easily connected using banana plugs, spade lugs or
bare wire (European models do not accept banana
plugs). See Section 3.3.

Page 10
Micro-Tech 600/1200/2400 Power Amplifiers
3 Installation
3.1 Mounting
Micro-Tech 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 provide support for the amplifier’s
back panel or secure it to the rack to help support the
unit’s weight.
Fig. 3.1 Mounting Dimensions
ODEP
CH1 CH2
POWER
OFF
19 in
48.3 cm
16 in
40.6 cm
3.5 in
8.9 cm
SIDE VIEW
Fig. 3.2 Top View of a Rack-Mounted Unit
AIR
FLOW
AIR FLOW
AMPLIFIER
(TOP VIEW)
RACK
CABINET
16 in
2 in
MIN.
17 in
AIR
FLOW
IMPORTANT: Be sure the back of
the amplifier is supported.
3.2 Cooling
Micro-Tech amplifiers include an internal fan that runs
when the unit is turned on. Before mounting your am-
plifier, 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 Fig-
ure 3.2). Also, open spaces in the rack should be cov-
ered to prevent heated air from the side exhaust vents
from being drawn into the front air intake.
BLOWER
(OPTION 2)
BLOWER
(OPTION 1)
AIR
FLOW
FRONT
OF
RACK
DOOR
AIR
FLOW
EQUIPMENT
RACK
(SIDE VIEW)
Fig. 3.3 Proper Air Flow with a Rack-Mounted Blower
You will know when your Micro-Tech amplifier has suffi-
cient 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 pro-
tect itself from overheating. If you experience a cooling
problem, you should consider several factors that may
be contributing to the problem, including load imped-
ance, 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
reasonableandyou stillhave a coolingproblem,check
for shorts in the loudspeaker cables, and look for prob-
lems with air flow or ambient air temperature.
Air flow restrictions are the most common cause of in-
adequate cooling. They may result from improper
mounting, bundles of power cords, clogged dust fil-
ters and closed rack doors. Mount the amplifier to al-
low sufficient air flow into the front intake, out the side
exhaust vents, and out the back of the rack. Move air
flow restrictions like bundled power cords out of the
way. Use the procedure in Section 4.5 to clean the air
filters. Leave rack doors 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%.
Ifyour ODEP indicators stilldim under demandingcon-
ditions, 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

Page 11
Micro-Tech 600/1200/2400 Power Amplifiers
the rack so it blows outside air into the space between
the door and the front of the amplifiers. This will pres-
surize the “chimney” behind the door (Figure 3.3, Op-
tion 1). The blower should not blow air into or take air
out of the space behind the amplifiers. For racks with-
out a front door, you can evacuate the rack by mount-
ing the blower at the top of the rack so air blows out the
back (Figure 3.3, Option 2). You can estimate a rack’s
required air flow by adding each unit’s maximum air
flow rating. Each Micro-Tech 600 and 1200 can move
35 cubic feet (1 cubic meter) of air per minute, and
each Micro-Tech 2400 can move 45 cubic feet (1.3
cubic meters) of air per minute. So if you put one of
each in a rack, you would need 115 cubic feet (3.2 cu-
bic meters) of air flow through the rack per minute un-
der worst-case conditions (35 cubic feet + 35 cubic
feet + 45 cubic feet = 115 cubic feet).
Another cooling problem to consider is high ambient
air temperature. If the ambient air temperature is ex-
tremely high, ODEP may reduce the output to protect
the amplifier even when it is receiving the maximum
recommended air flow. Under these unusual condi-
tions, it may be necessary to use air conditioning for
supplemental cooling. Air conditioning is rarely a ne-
cessity because internal fans and rack-mounted blow-
ers 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 Sec-
tion 7 for information on calculating the hourly thermal
dissipation of your system.
3.3 Wiring
The following section describes common ways to in-
stall your amplifier in a sound system. The input and
output terminals are located on the back panel. Please
use care when making connections, selecting signal
sources and controlling the output level. The load you
save may be your own! Crown assumes no liability for
damaged loads resulting from careless amplifier use
or deliberate overpowering.
CAUTION:When making or changing connections,
always disconnect the AC power and turn the level
controls off (fully counterclockwise). This is very im-
portant because it reduces the chance of loud blasts
that can cause loudspeaker damage.
Micro-Tech amplifiers may be operated in one of three
modes (Stereo, Bridge-Mono and Parallel-Mono) by
switching the stereo/mono switch on the back panel.
There are VERY IMPORTANT wiring differences among
these three modes which are discussed next.
3.3.1 Stereo (Two-Channel) Operation
In Stereo mode, installation is very intuitive: input chan-
nel1feedsoutputchannel 1,andinputchannel2 feeds
outputchannel 2. To put the amplifier into Stereomode,
first turn it off, then slide the stereo/mono switch to the
center position, and properly connect the output wir-
ing as shown in Figure 3.4. Each channel has a pair of
binding posts for easy loudspeaker cable connection.
Observe correct polarity, and be very careful not to
short the two channels together.
Fig. 3.4 Stereo Wiring
STEREO MODE
MIXER LOUDSPEAKERS
MICRO-TECH AMPLIFIER
+
–
+
–
CHANNEL 1
CHANNEL 2
CHANNEL 1
CHANNEL 2
STEREO
BRIDGE
MONO
PARALLEL
MONO
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH.
STEREO
BRIDGE
MONO
PARALLEL
MONO
CH-2 CH-1
CH.2
LEVEL
CONTROL
GROUND
LIFT
SWITCH
CH.1
LEVEL
CONTROL

Page 12
Micro-Tech 600/1200/2400 Power Amplifiers
CAUTION: In Stereo mode, never tie the amplifier’s
outputs directly together, and never parallel them
with the output of another amplifier. Such connec-
tions do not increase the output power and may acti-
vate 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 Section 3.3.3 if the
loadislessthan4 ohms).WiringforBridge-Monomode
isverydifferentfromtheothermodesand requiresspe-
cial 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
greatly degraded. Also, turn down the channel 2 level
control (fully counterclockwise).
Note: The channel 2 input and level control are not de-
featedinBridge-Mono mode. Any signal feeding chan-
nel 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
as shown in Figure 3.5. The positive (+) lead from the
loudspeaker connects to the red (+) channel 1 binding
post,and the negative(–) or groundleadfromthe loud-
speaker connects to the red (+) channel 2 binding
post. Do not connect the black (–) binding posts. Also,
the load must be balanced so neither lead is con-
nected to ground.
MIXER LOUDSPEAKER
–
+
ONLY USE THE CHANNEL 1 INPUT
DO NOT
USE DO NOT
USE BLACK
TERMINALS
STEREO
BRIDGE
MONO
PARALLEL
MONO
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH.
STEREO
BRIDGE
MONO
PARALLEL
MONO
CH-2 CH-1
TURN CHANNEL 2
OFF (FULLY CCW)
IN THIS MODE.
MICRO-TECH AMPLIFIER
Fig. 3.5 Bridge-Mono Wiring
BRIDGE-MONO MODE

Page 13
Micro-Tech 600/1200/2400 Power Amplifiers
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.
3.3.3 Parallel-Mono Operation
Parallel-Mono mode is used to drive loads with a total
impedance of less than 4 ohms (see Section 3.3.2 if
the load is 4 ohms or more). Installing the amplifier in
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
backpanel).Connectthe inputsignaltochannel 1only.
Fig. 3.6 Parallel-Mono Wiring
MIXER LOUDSPEAKER
–
+
ONLY USE THE CHANNEL 1 INPUT
CHANNEL 2 IS
NOT USED IN
THIS MODE.
MICRO-TECH AMPLIFIER
STEREO
BRIDGE
MONO
PARALLEL
MONO
CAUTION: TURN OFF AMPLIFIER
BEFORE CHANGING THIS SWITCH.
STEREO
BRIDGE
MONO
PARALLEL
MONO
CH-2 CH-1
ADD A 14 GAUGE
(OR LARGER)
JUMPER BETWEEN
THE RED CHANNEL 1
AND CHANNEL 2
BINDING POSTS.
PARALLEL-MONO MODE
The channel 2 input and level control are bypassed in
this mode, and should not be used.
Connect the load to the channel 1 output as shown in
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 black (–) channel 1 binding post. Finally, install a
jumper wire of at least 14 gauge between the red (+)
binding posts of both channels 1 and 2.
CAUTION: When wired for Parallel-Mono mode, do
not operate the amplifier in Stereo or Bridge-Mono
mode until the output wiring is reconfigured. Fail-
ure to do so will result in inefficient operation, high
distortion and excessive heating.

Page 14
Micro-Tech 600/1200/2400 Power Amplifiers
3.3.4 Input Connection
The balanced phone jack inputs have a nominal im-
pedance of 20 K ohms (10 K ohms with unbalanced
wiring) and will accept the line-level output of most de-
vices. Three-pin female XLR connectors are also avail-
able on the optional MT-XLR accessory and balanced
barrier block connectors are available on the optional
MT-BB accessory (see Section 8.2). Correct input wir-
ing will depend on two factors: (1) whether the input
signals are balanced or unbalanced, and (2) whether
the signal source floats or has a ground reference. Fig-
ures 3.7 and 3.8 provide examples of recommended
connection techniques for each type of signal source.
The optional MT-XLR connector is shown.
Fig. 3.7 Unbalanced Input Wiring
for the Optional MT-XLR
Twin-lead shielded cable
2-wire line cord
(or battery power)
Shield connected
to ground terminal
3-wire grounded line cord
(or other ground connection)
Shield is not
connected
at this end
Grounded
source
3-wire grounded line cord
(or other ground connection)
Input ground
terminal not used
Grounded
source
Single-conductor coax
or twisted pair
2-wire line cord
(or battery power)
Floating
source
Shield connected to both
negative (–) and ground
input terminals
+
–
INPUT
Output
Floating
source
+
3
1 2
+
–
INPUT
+
Output
3
1 2
+
–
INPUT
Output
+
3
1 2
+
–
+
Output
INPUT
3
1 2
3
1 2
+
–
INPUT
2-wire line cord
(or battery power)
Note: If two or more channels with
the same input ground reference
are driven from the same
floating source, connect
only one shield to the
source chassis.
Floating
source
3-wire grounded line cord
(or other ground connection)
Shield not connected
at this end
Grounded
source
3
1 2
Output +
–
+
–
Output +
–
INPUT
Fig. 3.8 Balanced Input Wiring
for the Optional MT-XLR
The amplifier’s built-in 1¦4-inch input phone connectors
can be wired similarly for balanced or unbalanced,
floatingor ground-referenced sources.Thephone con-
nectors have a standard tip-ring-sleeve (TRS) configu-
ration: the tip is positive (+), ring is negative (–) and
sleeve is ground (see Figure 3.9). Wiring for different
sourcesfollowsthe XLRwiring guidelines shownin Fig-
ures 3.7 and 3.8.
When either of the input connector accessories is in-
stalled, the unused input connectors can be used as
“daisy chain” outputs to feed the input signal from one
amplifier to another.
Please follow the input wiring instructions in Section
3.3.2 and 3.3.3 if the amplifier will be used in either
Bridge-Mono or Parallel-Mono mode. Remember, do
not use the channel 2 input in either mono mode.
Fig. 3.9 Balanced and Unbalanced
Phone Plug Wiring
+
–
SHIELD
BALANCED
+
SHIELD
UNBALANCED

Page 15
Micro-Tech 600/1200/2400 Power Amplifiers
SOLVING INPUT PROBLEMS
Sometimes large subsonic (subaudible) frequencies
are present in the input signal. These can damage
loudspeakers by overloading or overheating them. To
attenuate such frequencies, place a capacitor in se-
ries with the input signal line. The graph in Figure 3.10
shows some possible capacitor values and how they
affect frequency response. Use only low-leakage pa-
per, mylar or tantalum capacitors.
+
–
Balanced In
910Ω
.003
fµ
.015
fµ
.018
fµ
1.8 mH
2.5 mH
A
C
B
.015
fµ
1.8 mH
D
Balanced Out
+
–
910Ω
1.8 mH
2.5 mH
1.8 mH
+
–
Balanced In Balanced Out
+
–
+
–
Balanced In Balanced Out
+
–
+
–
Balanced In Balanced Out
+
–
0.47 Film
0.47 Film
1 Hz 10 Hz 100 Hz 1 kHz 10 kHz
dB
0
–5
–10
–15
Frequency
0.047 µf 0.1 µf 0.47 µf 1.0 µf 0.22 µf
Fig. 3.10 Subsonic Filter Capacitors
For balanced input wiring, use one of the examples in
Figure 3.12. Filters A, B and C correspond to the un-
balanced filters above. Filter D also incorporates the
subsonic filter described previously.
Another problem to avoid is grgr
grgr
ground loopsound loops
ound loopsound loops
ound loops. These are
undesired currents that flow in a grounded system and
Fig. 3.12 Balanced RF Filters
usually cause hum in the output. A common source of
ground loop problems is the placement of input cables
parallel to power cables or near power transformers.
The magnetic field that surrounds these conductors
can induce the 50 or 60 Hz alternating current into your
input cables. To prevent this type of ground loop, it is
always a good idea to locate input cables away from
power cables and power transformers. We also rec-
ommendusing shielded or twisted pair wire.Withloose
wires, use tie-wraps to bundle together each pair of
input wires. This helps reduce magnetically-induced
currentbyminimizingthe cross-sectionalareabetween
Input Wiring Tips
1. Use only shielded cable. Cables with
higher density shields are better. Spiral
wrapped shield is not recommended.
2. When using unbalanced lines, keep the
cables as short as possible. Avoid cable
lengths greater than 10 feet (3 meters).
3. Do not run signal cables together with
high-level wiring such as loudspeaker wires
or AC cords. This reduces the chance of hum
or noise being induced into the input cables.
4. Turn off the entire system before chang-
ing connections. Turn down the level controls
(fully counterclockwise) before powering the
system back up. Crown is not liable for dam-
age incurred when any transducer or com-
ponent is overdriven.
Another problem to avoid is the presence of large lev-
els of radio frequencies or RF in the input signal. Al-
though high RF levels may not pose a threat to the
amplifier, they can burn out tweeters or other loads that
are sensitive to high frequencies. Extremely high RF
levels may also cause the amplifier to prematurely ac-
tivate its protection circuitry. RF can be introduced into
an input signal by local radio stations or the bias signal
of many tape recorders. To prevent RF problems, in-
stall appropriate low-pass filters on the inputs. Ex-
amples are shown below for unbalanced wiring:
4 kHz 10 kHz 40 kHz 100 kHz
Fre
q
uenc
y
dB
0
–10
–20
A
B
C
6 dB/octave
12 dB/octave
To
Amp
GND
To
Amp
GND
To
Amp
GND
Source
1.8 K ohm
.003
fµ
.015
f
µ
.018
fµ
3.9 mH
5 mH
600 ohm
Source
R
600 ohm
Source
R
A
C
B
Note: A low source impedance (R) can be
increased to 600 ohms with an a
pp
ro
p
riate resistor.
Fig. 3.11 Unbalanced RF Filters

Page 16
Micro-Tech 600/1200/2400 Power Amplifiers
conductors that could bisect the magnetic field.
Ground loops will also occur when the input and out-
putgroundsaretied together.DONOTCONNECT THE
INPUT AND OUTPUT GROUNDS TOGETHER. Tying
the input and output grounds together can also cause
feedback oscillation from the load current flowing in
the loop. To avoid this problem use proper grounding,
isolate the inputs, and isolate other common AC de-
vices. If necessary, the input phone jack grounds can
be isolated from the AC mains (chassis) ground with
the ground lift switch located on the back panel of the
amplifier (see Figure 2.2 and Section 4.4).
3.3.5 Output Connection
Consider the power-handling capacity of your load be-
fore connecting it to the amplifier. Crown is not liable for
damage incurred at any time due to any load being
overpowered. The use of loudspeaker protection fuses
is highly recommended (see Section 3.3.6). Also,
please pay close attention to the precautions in Sec-
tion 4.1.
excellent damping factor can easily be negated by us-
ing insufficient loudspeaker cables.
Use the nomograph and the procedure that follow to
find the recommended American Wire Gauge (AWG)
or resistance per 1000 feet of wire for your system.
Use Good Connectors
1. To prevent possible short circuits, insu-
lateexposedloudspeaker cable connectors.
2. Do not use connectors that might acci-
dentally tie conductors together when mak-
ing or breaking connections (for example, a
standard three-wire stereo phone plug).
3. Never use connectors that can be
plugged into AC power receptacles.
4. Avoid using connectors with low current-
carrying capacity.
5. Do not use connectors that have any ten-
dency to short.
HOW TO DETERMINE
APPROPRIATE WIRE GAUGE
It is important to use loudspeaker cables with sufficient
gauge (thickness) for the length being used. The resis-
tance introduced by inadequate cables will reduce
both the output power and the motion control of the
loudspeakers. The latter problem occurs because the
damping factor decreases as cable resistance in-
creases. This is very important because the amplifier’s
40
30
20
15
10
9
8
7
6
5
4
3
2
1
2
5
10
20
50
100
.04
.06
.1
.2
.4
.6
1
2
4
6
10
20
40
8000
Ohms/1000 Feet
(305 Meters) AWG (American Wire Gauge)
Feet Meters
5000
1000
500
100
50
10
5
1
.5
.1
.05
.01
#28
#26
#24
#22
#20
#18
#16
#14
#12
#10
#8
#6
#4
#2
#0
#00
#0000
R
L
Load
Resistance
(Ohms)
R
L
R
S
Damping
Factor
R
S
Source
Resistance
(Ohms)
Two
Conductor
Cable
Copper
Wire
Example Shown:
Load Resistance = 8 ohms
Desired Damping Factor = 500
Source Resistance = 0.016 ohms
Cable Length = 10 feet (3.1 meters)
Recommended Wire: #8 AWG or equivalent
wire with 1.75 ohms or less resistance per
1000 feet (305 meters).
1
0.5
200
500
1,000
2,000
20,000
5,000
10,000
.01
.001
.02
.004
.006
.002
.0004
.0006
.0002
0.3
1.5
0.6
3.1
6.1
15.3
30.5
61.0
152.5
305.0
610.0
1525
1
5
2
10
20
50
100
200
500
1000
2000
5000
.0002
0.6
0.7
0.8
1.5
0.9
Fig. 3.13 Wire Size Nomograph

Page 17
Micro-Tech 600/1200/2400 Power Amplifiers
1. Note the load resistance of the loudspeakers connected
to each channel of the amplifier. Mark this value on the
“Load Resistance” line of the nomograph.
2. Select an acceptable damping factor and mark it on the
“Damping Factor” line. Your amplifier can provide an excel-
lent damping factor of 1,000 from 10 to 400 Hz in Stereo
mode with an 8 ohm load. In contrast, typical damping fac-
tors are 50 or lower at these frequencies. Higher damping
factors yield lower distortion and greater motion control over
the loudspeakers. A common damping factor for commer-
cial applications is between 50 and 100. Higher damping
factors may be desirable for live sound, but long cable
lengths often limit the highest damping factor that can be
achieved practically. (Under these circumstances, Crown’s
IQ System is often used so amplifiers can be easily moni-
tored and controlled when they are located very near the
loudspeakers.) In recording studios and home hi-fi, a damp-
ing factor of 500 or more is very desirable.
3. Draw a line through the two points with a pencil, and con-
tinue until it intersects the “Source Resistance” line.
4. On the “Two Conductor Cable” line, mark the length of
the cable run.
5. Draw a pencil line from the mark on the “Source Resis-
tance” line through the mark on the “Two Conductor Cable”
line and intersect the “Copper Wire” line.
6. The required wire gauge for the selected wire length and
damping factor is the value on the right-hand scale of the
“Copper Wire” line. For metric wire sizes, find the recom-
mended resistance in ohms per 305 meters (1000 feet) and
use this information to reference the correct wire size. Note:
Wire size increases as the AWG gets smaller .
7. If the size of the cable exceeds what you want to use,
(1) find a way to use shorter cables, like using the IQ Sys-
tem , (2) settle for a lower damping factor, or (3) use more
than one cable for each line. Options 1 and 2 will require the
substitution of new values for cable length or damping factor
in the nomograph. For option 3, doubling the number of
conductors of equal thickness will reduce the resistance in
ohms per 1000 feet (305 meters) by half. When using AWG
standards, you can estimate the effective wire gauge by
subtracting 3 from the given wire gauge every time the num-
ber of conductors of equal gauge is doubled. So, if #10 wire
is too large, two #13 wires can be substituted, or four #16
wires can be used for the same effect.
SOLVING OUTPUT PROBLEMS
High-frequency oscillations can cause your ampli-
fier to prematurely activate its protection circuitry. The
effects of this problem are similar to the effects of the
RF problems described in Section 3.3.4. To prevent
high-frequency oscillations, follow these guidelines:
1. When using long cable runs, or when different
amplifiers share a common cable tray or jacket,
use tie-wraps to bundle individual conductors
so the wires for each loudspeaker are kept
close together. Do not bundle wires from differ-
ent amplifiers. This reduces the chance of con-
ductors acting like antennas that transmit or
receive the high frequencies that can cause os-
cillations.
2. Avoid using shielded loudspeaker cable.
3. Never tie together input and output grounds.
4. Never tie together different amplifier outputs.
5. Keep output cables separated from input
cables.
6. Install an RF filter in series with each input (see
Section 3.3.4).
7. Install input wiring according to the instructions
in Section 3.3.4.
Another problem to avoid is the presence of large sub-
sonic currents when primarily inductive loads are
used. Examples of inductive loads are 70-volt step-up
transformers and electrostatic loudspeakers.
Inductive loads can act like a short circuit at low fre-
quencies. This can cause the amplifier to produce
large low-frequency currents and activate its protec-
tion circuitry. Always take the precaution of installing a
subsonic filter in series with each of the amplifier’s in-
puts when inductive loads are used. A three-pole, 18
dB per octave filter with a –3 dB frequency of 50 Hz is
recommended(someapplications may benefit froman
even higher –3 dB frequency). See Section 3.3.4 for
some examples.
Another way to protect inductive loads from large low-
frequency currents and to prevent the amplifier from
prematurely activating its protective systems is to par-
allel a 590 to 708 mF nonpolarized motor start capaci-
tor and a 4-ohm, 20-watt resistor in series with the
amplifier’s output and the positive (+) lead of the trans-
former. This circuitis shown in Figure3.14.It uses com-
ponents that are available from most electrical supply
stores.
4-ohm, 20-watt
Resistor
590 to 708 µf Capacitor
120 VAC, N.P.
+
–
Inductive
Load
+
–
From
Amplifier
Output
Fig. 3.14 Low-Frequency Protection
Circuit for Inductive Loads

Page 18
Micro-Tech 600/1200/2400 Power Amplifiers
A better approach is to fuse each driver independently.
This allows you to apply the most appropriate protec-
tion for the type of driver being used. In general, low-
frequency drivers (woofers) are the most susceptible
to thermal damage and high-frequency drivers (tweet-
ers) are usually damaged by large transient voltages.
This means that your loudspeakers will tend to have
better protection when the woofers are protected by
slow-blow fuses and high-frequency drivers are pro-
tected by high-speed instrument fuses.
3.4 AC Mains Power Requirements
All Micro-Tech amplifiers are shipped with an appropri-
ate line cord and plug. The standard cord and plug for
each model are listed by country (or region) in Fig-
ure 3.16. When possible, use a power receptacle on a
dedicated circuit, and always make sure it will provide
the right voltage with sufficient current. We do not rec-
ommend operating your amplifier with voltages greater
than 10% above or below the unit’s rated voltage. For
example, an amplifier rated for 120 VAC operaton
should not exceed 132 VAC. See Section 7 for power
requirements under a variety of conditions.
3.3.6 Additional Load Protection
Micro-Tech amplifiers can deliver very high power lev-
els, so it’s a good idea to add some protection if its not
alreadybuiltintoyour loudspeakers.Loudpseakers are
subject to thermal damage from sustained overpower-
ing and mechanical damage from large transient volt-
ages. In both cases, fuses may be used to protect your
loudspeakers.
Thermal protection and voltage protection require dif-
ferent types of fuses. Slow-blow fuses are used to pre-
ventthermaldamage becausethey respondtothermal
conditions like a loudspeaker. High-speed instrument
fuses like the Littlefuse 361000 series are used to pro-
tect loudspeakers from transient voltages. The nomo-
graph in Figure 3.15 can be used to select the correct
fuse for thermal or voltage protection.
There are two common ways to install the fuses. One
approach is to put a single fuse in series with each
output. This is easy because there is only one fuse per
channel to install. But if the fuse blows, power is re-
moved from all of the connected loads.
All specifications in this manual were measured using
120 VAC, 60 Hz power mains unless otherwise noted.
Specifications are derived using a mains voltage that
is accurate to within 0.5% with THD less than 1.0%
under all testing conditions. Performance variations
canoccur at other ACmains voltages and linefrequen-
cies. In addition, line regulation problems will directly
affect the output power available from the amplifier.
Fig. 3.15 Loudspeaker Fuse Nomograph
Fig. 3.16 AC Mains Cords and Plugs
Country or Region Micro-Tech
600
Cord Plug Cord Plug
Australia, New Zealand
Brazil, Guam, Hong Kong,
Jamaica, Japan, Peru,
Phillipines, Singapore,
Tahiti, Taiwan, Thailand,
Venezuela
NEMA
5-15P 14/3 SJT NEMA 5-15P 12/3 SO NEMA 5-15P
1.5 mm
2
AS 3112
10 A
14/3 SJT
BS 546
BS1363
1.5 mm
2
1.5 mm
2
BS 546
BS1363
1.5 mm
2
1.5 mm
2
BS 546
BS1363
1.5 mm
2
1.5 mm
2
Central America,
North America
NEMA
5-15P 14/3 SJT NEMA 5-15P 12/3 SO NEMA 5-20P
14/3 SJT
India, South Africa
Ireland, Norway,
United Kingdom,
United Arab Emirates
1.5 mm
2
AS 3112
10 A 1.5 mm
2
Micro-Tech
1200 Cord
AS 3112
15 A
Argentina, Austria, China,
Denmark, Finland, France,
Germany, Greece, Holland,
Indonesia, Italy, Korea,
Malaysia, Portugal, Spain,
Sweden, Switzerland,
Turkey
1.5 mm
2
CEE 7/7 1.5 mm
2
CEE 7/7 1.5 mm
2
CEE 7/7
Plug
Micro-Tech
2400
1.0
1.2
1.4
1.6
2.5
3
4
5
6
7
8
9
10
12
14
16
20
25
30
20
15
10
8
6
5
4
3
2
1.5
1
.8
.6
.5
.4
.3
.2
.15
.1
.08
3000
2000
1500
1000
800
600
400
300
200
150
100
80
60
40
30
20
15
10
8
6
4
3
2
1.5
1
LOUDSPEAKER IMPEDANCE
(ohms)
FUSE
(amps)
LOUDSPEAKER RATING
PEAK MUSIC POWER
(watts) (Typically 4 times the continuous average power)
Answer: Fuse = 1.5 A
2
40
Example:
Impedance = 8 ohms.
Peak Power = 75 W

Page 19
Micro-Tech 600/1200/2400 Power Amplifiers
4 Operation
4.1 Precautions
Although your amplifier is protected from internal and
external faults, you should still take the following pre-
cautions for optimum perfromance and safety:
1. Improper wiring for the Stereo, Bridge-Mono and
Parallel-Mono modes can result in serious operat-
ing difficulties (see Section 3.3).
2. WARNING: Do not change the position of the
stereo/mono switch unless the amplifier is first
turned off.
3. CAUTION: In Parallel-Mono mode, a jumper is
used between the red (+) channel 1 and 2 red
output binding posts. Remove this jumper for
Bridge-Mono and Stereo modes, or high distor-
tion and excessive heating will occur. Also,
check the stereo/mono switch for proper setting.
4. Turn off the amplifier and unplug it from the AC
mains before removing the back panel cover plate
or before removing and cleaning the dust filter.
5. Use care when making connections, selecting sig-
nal sources and controlling the output level. The
load you save may be your own!
6. Do not short the ground lead of an output cable to
the input signal ground. This will form a ground loop
and may cause oscillations.
7. Operate the amplifier from AC mains of not more
than 10% above or below the selected line voltage
and only at the specified line frequency.
8. Never connect the output to a power supply out-
put, battery or power main. Such connections
may result in electrical shock.
9. Tampering with the circuitry by unqualified person-
nel or making unauthorized circuit changes may be
hazardous and invalidates all agency listings.
Remember: Crown is not liable for damage that results
from overdriving other system components.
4.2 Indicators
The amber enable indicator is provided to show that
the amplifier has been turned on (or enabled), and its
low-voltage power supply and forced-air cooling sys-
tem are working. It does not indicate the status of the
high-voltage power supplies. For example, the enable
indicator will remain lit during unusual conditions that
would cause the amplifier’s protection systems to tem-
porarily remove power from a high-voltage power sup-
ply (see Section 4.3).
The amber ODEP indicators confirm the normal op-
eration of Crown’s patented Output Device Emulation
Protection circuitry. During normal operation, they glow
brightly to show the presence of reserve thermody-
namic energy. They dim proportionally as the energy
reserve decreases. In the rare event that there is no
reserve, the indicators turn off and ODEP proportion-
ally limits the drive level of the output stages so the
amplifier can continue safe operation even when con-
ditions are severe. (For a more detailed description of
ODEP , see Section 4.3.1.)
The ODEP indicators also turn off if the amplifier loses
AC power, the power switch is turned off, or the low-
voltage power supply fuse blows. The ODEP indicator
for the affected channel will turn off if a high-voltage
power supply fuse or breaker blows, or if the channel
activates transformer thermal protection. Conditions
that activate “drive protection” do not affect the ODEP
indicators (see Section 4.3.3).
4.3 Protection Systems
Micro-Tech amplifiers have extensive protection sys-
tems including ODEP , ultrasonic/RF protection, drive
protection, and power supply fuses or breakers.
4.3.1 ODEP
Crowninvented ODEP tosolvetwolong-standing prob-
lems in amplifier design: to prevent amplifier shutdown
during demanding operation, and to increase the effi-
ciency of the output circuitry.
To do this, Crown established a rigorous program to
measure the safe operating area (SOA) of each output
transistorbeforeinstalling itin an amplifier. Next,Crown
designed intelligent circuitry to simulate the instanta-
neous operating conditions of those output transistors.
Its name describes what it does: Output Device Emu-
lation Protection or ODEP . In addition to simulating out-
put transistor operating conditions, it compares their
operation to their known SOA. If ODEP sees that more
ODEP
CH1 CH2
POWER
OFF
Fig. 4.1 Indicators

Page 20
Micro-Tech 600/1200/2400 Power Amplifiers
4.3.4 Transformer Thermal Protection
All Micro-Tech amplifiers have transformer thermal pro-
tection. The amplifier’s transformer thermal protection
circuitry is activated in very unusual circumstances
where the unit’s transformer temperature rises to un-
safe levels. Under these abnormal conditions, the am-
plifier will remove power from the affected channel’s
high-voltage power supply which puts the channel in
drive protection mode. The amplifier channel will re-
turn to normal operation after its transformer cools to a
safe temperature.
It is extremely unlikely that you will ever see a
Micro-Tech amplifier activate transformer thermal pro-
tection as long as it is operated within rated conditions
(see Section 6). One reason is that ODEP keeps the
amplifier working under very severe conditions. Even
so, higher than rated output levels, excessively low-
impedance loads and unreasonably high input signals
can generate more heat in the transformer than in the
outputdevices. These conditions can overheat a trans-
former and activate its protection system.
Micro-Tech amplifiers are designed to keep working
under conditions where other amplifiers would fail. But
even when a Micro-Tech’s limits are exceeded, it will
stillprotectitself—andyourinvestment—fromdamage.
4.3.5 Fuses and Circuit Breakers
120 VAC, 60 Hz models and all Micro-Tech 2400s have
an internal fuse that protects the low-voltage supply
and cooling fan. Micro-Tech 600 and 1200 high-volt-
age supplies are protected by internal fuses, while Mi-
cro-Tech 2400 high-voltage supplies are protected by
circuit breakers. With rated loads and output levels,
the fuses (or circuit breakers) should only shut down
the amplifier in the rare instance of a catastrophic fail-
ure. ODEP protection keeps the amplifier operational
under most other severe conditions. The fuses (or cir-
cuitbreakers)canalsoshutdownthe amplifierincases
where extremely low-impedance loads and high out-
put levels result in current draw that exceeds their rat-
ing.Again,thisshould onlybepossiblewhen operating
outside rated conditions like when the amplifier is used
to drive a 1 ohm load in Stereo mode, or when an input
signal is clipped severely.
Micro-Tech amplifiers do not blow their fuses or trip
their breakers unless something is wrong. In the rare
event that an internal fuse blows, please refer the unit
to a qualified technician. If a breaker in a Micro-Tech
2400 trips, try to identify and correct the problem be-
fore resetting the breakers. If the problem persists, re-
fer the unit to a qualified technician.
power is needed from the output devices than they
can deliver under the present conditions, ODEP imme-
diately limits the drive level until it falls within the SOA.
Limiting is proportional and kept to an absolute mini-
mum—only what is required to prevent damage. Un-
dernormal conditions,nolimitingisrequiredand ODEP
is transparent to the audio signal.
This level of protection enables Crown to increase out-
put efficiency to never-before-achieved levels while
greatly increasing reliability. As described previously,
ODEP operation is monitored by the front panel ODEP
indicators. They show whether the amplifier is function-
ing correctly or if ODEP is limiting the drive level.
With ODEP you get maximum power with maximum
protection so the show goes on.
4.3.2 Ultrasonic and Radio Frequency Protection
Micro-Tech amplifiers have a controlled slew rate. This
means that their design limits the frequencies they can
reproduce. At the same time, the amplifier’s controlled
slew rate has no effect on its audio performance be-
cause limiting occurs well above 20 kHz. This ap-
proach protects the amplifier from radio frequencies,
and also protects some sensitive loads (like tweeters).
In the real world, an amplifier’s slew rate only needs to
be large enough to deliver the maximum voltage at the
highest required frequency—higher slew rates actu-
ally allow the reproduction of undesirable frequencies.
4.3.3 Drive Protection
The drive protection system temporarily removes drive
from the output stages to protect the amplifier and its
load(s). Drive protection can be activated in two situa-
tions. First, if dangerous subsonic frequencies or di-
rect current (DC) is detected in the amplifier’s output,
the unit will activate its DC/low-frequency protection
circuitry which puts the affected channel in drive pro-
tection mode. This protects the load(s) and prevents
oscillation. The amplifier resumes normal operation
when it no longer detects dangerous output. Although
it is extremely unlikely that you will ever activate the
amplifier’s DC/low-frequency protection system, im-
proper source materials like subsonic square waves or
a severely clipped signal can activate this system.
Theamplifier’sfault protection system puts theaffected
channel into drive protection mode in rare situations
where heavy common-mode current is detected in its
output. The amplifier should never output heavy com-
mon-mode current unless its circuitry is damaged.
Activating drive protection helps prevent further dam-
age.