DC-300A II

CHANNEL 1

CHANNEL 2

Some models may be exported under the name Amcron.
Applies only to 120 VAC North American units.
1996 by Crown International, Inc., P.O. Box 1000, Elkhart, Indiana 46515-1000 U.S.A. Telephone: 219-294-8000. The DC-300A II is produced by the Professional Audio Division of Crown International, Inc. Trademark Notice: Amcron Crown Com-Tech IOC IQ , , , , System and Macro-Tech are registered trademarks of Crown International, Inc. Other trademarks are the property of their respective owners.

K80002D9 5/96

THREE YEAR FULL WARRANTY

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, the ORIGINAL PURCHASER and ANY SUBSEQUENT OWNER of each NEW Crown1 product, for a period of three (3) years from the date of purchase by the original purchaser (the warranty period) that the new Crown product is free of defects in materials and workmanship, and we further warrant the new Crown product regardless of the reason for failure, except as excluded in this Crown Warranty.

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 product, for a period of three (3) years from the date of purchase by the original purchaser (the warranty period) that the new Crown product is free of defects in materials and workmanship. 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 the defective or malfunctioning product available to us free and clear of all liens or other encumbrances. The refund will be equal to the actual purchase price, not including interest, insurance, closing costs, and other finance charges less a reasonable depreciation on the product from the date of original purchase. Warranty work can only be performed at our authorized service centers or at the factory. We will remedy the defect and ship the product from the service center or our factory within a reasonable time after receipt of the defective product at our authorized service center or our factory. All expenses in remedying the defect, including surface shipping costs in the United States, will be borne by us. (You must bear the expense of shipping the product between any foreign country and the port of entry in the United States and all taxes, duties, and other customs fees for such foreign shipments.) 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 No person has the authority to enlarge, amend, or modify this Crown Warranty. This Crown Warranty is not extended by the length of time which you are deprived of the use of the new Crown product. Repairs and replacement parts provided under the terms of this Crown Warranty shall carry only the unexpired portion of this Crown Warranty. 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 MAY ALSO HAVE OTHER RIGHTS WHICH VARY FROM STATE TO STATE. No action to enforce this Crown Warranty shall be commenced later than ninety (90) days after expiration of the warranty period. THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERS CONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.

Note: If your unit bears the name Amcron, please substitute it for the name Crown in this warranty.
ITEMS EXCLUDED FROM THIS CROWN WARRANTY This Crown Warranty is in effect only for failure of a new Crown product which occurred within the Warranty Period. It does not cover any product which has been damaged because of any intentional misuse, accident, negligence, or loss which is covered under any of your insurance contracts. This Crown Warranty also does not extend to the new Crown product if the serial number has been defaced, altered, or removed. 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 the defective or malfunctioning product available to us free and clear of all liens or other encumbrances. The refund will be equal to the actual purchase price, not including interest, insurance, closing costs, and other finance charges less a reasonable depreciation on the product from the date of original purchase. Warranty work can only be performed at our authorized service centers. We will remedy the defect and ship the product from the service center within a reasonable time after receipt of the defective product at our authorized service center. All expenses in remedying the defect, including surface shipping costs to the nearest authorized service center, will be borne by us. (You must bear the expense of all taxes, duties and other customs fees when transporting the product.) 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. 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 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. 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 which you are deprived of the use of the new Crown product. Repairs and replacement parts provided under the terms of this Crown Warranty shall carry only the unexpired portion of this Crown Warranty. 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 No action to enforce this Crown Warranty shall be commenced later than ninety (90) days after expiration of the warranty period. THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERS CONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.

Telephone: 219-294-8200. Facsimile: 219-294-8301
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 (North America, Puerto Rico and Virgin Islands) or 219-294-8200 Fax: 219-294-8301 Fax Back: 800-294-4094 (North America only) or 219-293-9200 Internet: http://www.crownintl.com

CAUTION

RISK OF ELECTRIC SHOCK DO NOT OPEN
RISQUE DE CHOC LECTRIQUE NOUVREZ PAS
TO PREVENT ELECTRIC SHOCK DO NOT REMOVE TOP OR BOTTOM COVERS. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
PRVENIR LE CHOC LECTRIQUE NENLEVEZ PAS LES COUVERCLES. IL NY A PAS DES PARTIES SERVICEABLE LINTRIEUR. TOUS REPARATIONS DOIT ETRE FAIRE PAR PERSONNEL QUALIFI SEULMENT.

Magnetic Field

CAUTION! Do not locate sensitive high-gain equipment such as preamplifiers or tape decks directly above or below the unit. Because this amplifier has a high power density, it has a strong magnetic field which can induce hum into unshielded devices that are located nearby. The field is strongest just above and below the unit. If an equipment rack is used, we recommend locating the amplifier(s) in the bottom of the rack and the preamplifier or other sensitive equipment at the top.

WARNING

TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE!
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.
Printed on recycled paper.
DC-300A II Power Amplifier

CONTENTS

1 Welcome... 7 1.1 Unpacking.. 7 1.2 Features... Facilities... Installation... 9 3.1 Mounting... 9 3.2 Cooling.. 9 3.3 Wiring... 9 3.3.1 Mode of Operation.. 9 3.3.2 Input Connection.. 11 3.3.3 Output Connection.. 12 3.3.4 Additional Load Protection.. 13 3.3.5 AC Mains Power Requirement.. Operation... 15 4.1 Precautions... 15 4.2 Indicators... 15 4.3 Controls... 15 4.4 Protection... 15 4.5 Fuse Replacement.. Technical Information... 17 5.1 Principles of Operation... Specifications... Internal Settings.. 23 7.dB Gain vs. 0.775 V Input Sensitivity.. 23 7.2 Changing the Input Sensitivity to 0.775 V. Service.... 24 8.1 Worldwide Service... 24 8.2 North American Service.. 24 8.2.1 Service at a North American Service Center. 24 8.2.2 Factory Service.. 24

1.2 Features

Your dual channel (stereo) amplifier can be configured for higher-powered single channel operation. It also provides the following features:
AB+B class circuitry for maximum efficiency with minimum crossover notch distortion. IOC (Input/Output Comparator) alerts of distortion exceeding 0.05% to provide proof of performance. Ultra-low harmonic and intermodulation distortion result in the best dynamic transfer function in industry. Very low noise level and wide dynamic range exceed digital audio standards. Exclusive JTS (Junction Temperature Simulation) circuitry protects the output devices and provides exceptional dynamic headroom. High damping factor gives you greater loudspeaker motion control. Bridge-Mono output can drive 70 volt constant voltage lines without expensive, distortion-producing step-up transformers. Convection cooling with integrated heat sink/chassis design for maintenance-free operation.

1.1 Unpacking

Please unpack and inspect your new amplifier for any damage that may have occurred during transit. If damage is found, notify the transportation company imme-
Mounts in a standard 19 inch (48.3 cm) rack. Three year No-Fault full warranty protects your investment and guarantees the specifications of units in North America and other select countries.

Page 7

OUTPUT CHANNEL INPUT 1
OUTPUT CHANNEL 1 LINE FUSE AC

DUAL MONO

INTERNATIONAL, INC. ELECTRONIC EQUIPMENT
ELKHART, IN 46517 MADE IN U.S.A. SERIAL NUMBER

0000 000000

Fig. 2.1 Facilities

2 Facilities

A. Power Indicator
This indicator glows when the amplifier is turned on. Mono mode. In Bridge-Mono mode, the channel 2 input should not be used, its level control should be turned down and only balanced (ungrounded) loads should be connected to the output (see section 3.3.1).

B. Power Switch

This push button turns the DC-300A II on and off. The unit has no turn-on delay and minimal thumps. Always turn the amplifier on last so the turn-on transients of other components will not be amplified.

F. Fuse Holder

The AC line is safely fused. Use a 10 amp, 250 volt, type AB fuse for 100 and 120 VAC operation, or a 5 amp, 250 volt, type MTH fuse for 200, 220 and 240 VAC units (see Sections 3.3.5 and 4.5).

C. Input Jacks

An unbalanced inch phone jack is used for input to each channel. Do not use the channel 2 input in BridgeMono mode.

G. Level Controls

The output level of each channel is adjusted with these controls. Turn the channel 2 level control down completely when using Bridge-Mono mode.

D. Output Jacks

5-way binding posts provide output from each channel. Use banana plugs, spade lugs or bare wire to connect loudspeaker cables. In Bridge-Mono mode, connect the positive (+) loudspeaker terminal to the positive (+) channel 1 output and the negative () loudspeaker terminal to the positive (+) channel 2 output.

H. Power Cord

The unit has a grounded, three wire AC cord and plug.

I. IOC Indicators

The red Input/Output Comparator (IOC) indicators provide proof of distortion-free performance. Normally off, they flash in the rare event that the output waveform differs from the input by 0.05% or more.

E. Dual-Mono Switch

Facing the back of the amplifier, slide this switch to the left for Dual (stereo) mode and to the right for BridgePage 8

3 Installation

Your amplifier is designed for standard 19 inch (48.3 cm) rack mounting. Before mounting, determine whether you need to change the amplifiers internal settings for your application. Your amplifiers internal settings make it possible to change the input sensitivity from the default 26 dB gain to a sensitivity of 0.775 volts. If you need to operate your amplifier with an input sensitivity of 0.775 volts, or if you want more information on input sensitivity, please refer to Section 7 before proceeding. mounting, we recommend that you allow a 1.75 inch (4.45 cm) space above and below the unit. If you mount it with the front panel up, be sure to provide air space above and below the unit. Inadequate cooling can cause the built-in thermal protection circuitry to be activated prematurely. Overheating like this can also cause the front panel to become warm. Applications requiring sustained use at high output power levels may require the installation of a cooling fan.

3.3 Wiring

Figure 3.2 depicts three of the most common ways to install a DC-300A II in a sound system. All input and output jacks are located on the back panel. Please use care in making connections, selecting signal sources and controlling the output level. The load you save may be your own! Crown is not liable for any damage done to loads due to careless amplifier usage and deliberate overpowering. 3.3.1 Mode of Operation The DC-300A II may be operated in either Dual (stereo) or Bridge-Mono mode by setting the Dual-Mono switch on the back panel of the amplifier. There are very important wiring differences between these two modes which are discussed next. DUAL Dual mode installation is intuitive. The channel 1 input feeds the channel 1 output, and the channel 2 input feeds the channel 2 output. To put the amplifier in Dual mode, turn off the amplifier and slide the Dual-Mono switch to the left as you face the amplifiers back panel (see Figure 3.2). Be careful not to short the outputs together, and observe correct loudspeaker polarity. CAUTION: Do not tie the two outputs together. Never tie an output to another amplifiers output.

3.1 Mounting

The DC-300A II can be mounted into a standard 19 inch (48.3 cm) wide equipment rack. It occupies 7 inches (17.8 cm) of vertical rack space. Mounting screws and washers are provided with the unit. Although units can be stacked, this practice is not recommended. Instead, mount multiple units in a rack leaving air space between them. Also, before mounting the amplifier, please read about the amplifiers cooling requirements in the section that follows.

1.5 in 3.8 cm

5.5 in 14 cm

7 in 17.8 cm

19 in 48.3 cm

10.5 in 26.7 cm

0.875 in 2.2 cm
Fig. 3.1 Mounting Dimensions

3.2 Cooling

Your amplifier does not have a cooling fan. To prevent overheating, sufficient ventilation is required. Equipment racks or cabinets should have perforated top and bottom panels. This is especially important if more than one amplifier will be mounted in the same rack. When
MONO Amplifier installation in Bridge-Mono mode is very different. First, only the channel 1 input should be used. DO NOT USE THE CHANNEL 2 INPUT. For best results, disconnect all channel 2 input sources and turn the channel 2 level control fully counterclockwise (off). Note: The channel 2 input and level control are not defeated in bridge-mono mode. A signal fed to channel 2 will work against the signal feeding channel 1. To activate Bridge-Mono, move the Dual-Mono switch to the right as you face the amplifiers back panel. Both

Page 9

CHANNEL 2 CHANNEL 1

DUAL MODE

OUTPUT CHANNEL INPUT 1 OUTPUT CHANNEL 1 LINE FUSE AC
INTERNATIONAL, INC. ELECTRONIC EQUIPMENT

DC-300A II AMP

CHANNEL 2 (+) CHANNEL 1 (+)
BRIDGE-MONO MODE (METHOD 1)
OUTPUT CHANNEL INPUT 1 OUTPUT CHANNEL 1 LINE FUSE AC DUAL MONO
CHANNEL 2 (POLARITY MUST BE INVERTED)
BRIDGE-MONO MODE (METHOD 2)
Fig. 3.2 System Connection Page 10
outputs will receive the channel 1 input. The channel 2 output is inverted so it can be bridged with channel 1. There are two different ways to connect Bridge-Mono wiring. The most common method is to connect the positive (+) output of channel 1 to the positive (+) loudspeaker lead, and the positive (+) output of channel 2 to the negative () loudspeaker lead (see Figure 3.2). The negative amplifier outputs are not used. In Bridge-Mono mode, it is also possible to connect a loudspeaker to each output channel, however, the output of channel 2 is inverted. To compensate for this, you can invert the polarity of the channel 2 output wiring. First, connect a loudspeaker to channel 1 as you would normally. Then, connect a loudspeaker to channel 2 so its positive (+) output goes to the negative () loudspeaker terminal, and negative () output goes to the positive (+) loudspeaker terminal. CAUTION: Only connect balanced loads to a bridgemono output. Output lines must be isolated from ground or severe oscillations may occur. 3.3.2 Input Connection The unbalanced inch phone inputs have a typical impedance of 25 K ohms. They accept the line level output from most devices. Figure 3.3 shows how to properly wire both balanced and unbalanced lines.

FROM UNBALANCED SOURCE

SHIELD

0.1 Hz

100 Hz

Frequency

Fig. 3.4 Subsonic Filter Capacitors
are sensitive to high frequencies. Extremely high RF levels can also cause your amplifier to prematurely activate its protection circuitry, resulting in inefficient operation. RF can be introduced into a signal by local radio stations and from the bias signal of many tape recorders. To prevent this from happening, place an appropriate low-pass filter on the input(s). Some examples are shown below for unbalanced wiring.
1.8 K ohm Source A 3.9 mH R 600 ohm Source B 5 mH R 600 ohm Source C.018 f.015 f.003 f To Amp GND To Amp GND To Amp GND
4 kHz 10 kHz 40 kHz 100 kHz 6 dB/octave A B C dB 0

12 dB/octave

Note: A low source impedance (R) can be increased to 600 ohms with an appropriate resistor.

UNBALANCED INPUT

Fig. 3.5 Unbalanced RFI Filters

FROM BALANCED SOURCE

DROP SHIELD
For balanced input wiring, use one of the examples in Figure 3.6. Filters A, B and C correspond to the unbalanced filters above. Filter D also incorporates the subsonic filter described previously.

Balanced In 910 .003 f

Balanced Out

Fig. 3.3 Input Wiring

1.8 mH
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 series with the input signal line. The graph in Figure 3.4 shows some possible capacitor values and how they affect frequency response. Use only a low-leakage paper, mylar or tantalum capacitor. Another problem to avoid is the presence of large levels of radio frequencies or RF in the input signal. Although high RF levels may not pose a threat to the amplifier, they can burn out tweeters or other loads that

Balanced In.015 f

2.5 mH

Balanced In.018 f

0.47 Film 1.8 mH
Balanced In.015 f 0.47 Film 1.8 mH
Fig. 3.6 Balanced RFI Filters Page 11

3.3.3 Output Connection Consider the power-handling capacity of your load before connecting it. Crown is not liable for damage incurred at any time due to a load being overpowered. The use of loudspeaker protection fuses is highly recommended (see Section 3.3.4). Also, please pay close attention to the precautions in Section 4.1.

Page 12

3. Draw a line through the two points with a pencil, and continue until it intersects the Source Resistance line. 4. On the 2-Cond. Cable line, mark the length of cable run. 5. Draw a pencil line from the mark on the Source Resistance line through the mark on the 2-Cond. Cable line, and on to intersect the Annealed Copper Wire line. 6. The required wire gauge for the selected wire length and damping factor is the value on the Annealed Copper Wire line. 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, (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, estimate the effective wire gauge by subtracting 3 from the apparent wire gauge every time the number 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.
filters described in Section 3.3.2. 5. Install the input wiring according to the instructions in Section 3.3.2. Another problem to avoid is the presence of large subsonic currents when primarily inductive loads are used. Examples of inductive loads are 70 volt step-up transformers and electrostatic loudspeakers. Inductive loads can appear as a short at low frequencies, causing the amplifier to produce large low-frequency currents and unnecessarily activate its protection circuitry. Always take the precaution of installing a high-pass filter on the amplifier inputs when a predominantly inductive load is used. A three pole (18 dB per octave) filter with a 3 dB frequency of 50 Hz is recommended. (Depending on the system, it may be preferable to use a filter with a higher 3 dB frequency.) Such a filter can eliminate the subsonic frequency problems mentioned in Section 3.3.2. Another way to prevent the amplifier from activating its protection systems early and protect inductive loads from large low-frequency currents is to connect a 590 to 708 F nonpolarized capacitor and a 4 ohm, 20 watt resistor at the output of the amplifier in series with the positive (+) lead of the transformer. This is depicted in Figure 3.8.

1.0 1.2 1.4 1.2.400 3000

1. Turn the amplifier off and disconnect it from the AC mains. 2. Remove the perforated top cover by removing the 12 phillips screws that hold it in place. 3. Find the power transformer. The terminal strip with six connector tabs is wired to the transformer. 4. Change the appropriate jumpers for the desired operating voltage (see Figure 3.10). 5. Make sure the proper fuse is installed. Use only a 5 amp, 250 volt, type MTH fuse for AC mains of 200 volts or more; use only a 10 amp, 250 volt, type AB fuse for AC mains below 200 volts. 6. Carefully check all connections. 7. Repeat steps 1 and 2 in reverse order to reassemble the unit.
Example: Impedance = 8 ohms. Peak Power = 75 W Answer: Fuse = 1.5 A

150 100

1.5 1.8.6.5
(Typically 4 times the continuous average power)
IMPORTANT: Use only a 5 amp, 250 volt, type MTH fuse for 200, 220 or 240 VAC operation; use only a 10 amp, 250 volt, type AB fuse for 100 or 120 VAC operation.
GRNWHT BLKGRN YELRED BLUYEL WHT BLK
LOUDSPEAKER IMPEDANCE (ohms)

LOUDSPEAKER RATING

2 1.5 1

FUSE (amps)

PEAK MUSIC POWER (watts)

A B C D E F

Fig. 3.9 Fuse Selector Nomograph
3.3.5 AC Mains Power Requirement All units have a standard three wire, grounded AC cord and plug as specified by UL requirements for North American 120 VAC, 60 Hz units. Note: Crown assumes no liability whatsoever for ungrounded operation, nor for violation of UL or local electrical codes. Five standard line voltages are supported, including 100, 120, 200, 220 and 240 VAC. The unit may be operated at AC mains frequencies from 50 to 400 Hz. The model-voltage sticker on the back panel indicates the units factory configuration. WARNING: Risk of electric shock! Only a qualified technician should attempt to alter your amplifiers AC mains voltage configuration. To operate your amplifier at a different line voltage, you will need a phillips screwdriver. Then follow these steps:

Page 14

WHT ORN
Fig. 3.10 AC Mains Voltage Conversion

4 Operation

4.1 Precautions
Your amplifier is protected from all external faults. Even so, you should take the following precautions: 1. When the level of an input source is uncertain, or an audio component has not been previously used with your amplifier, always begin with the level controls at a minimum and gradually increase them while monitoring the output level. This approach helps avoid loudspeaker blasts. 2. Dont forget, your amplifier does not have a turn on delay. Beware of turn-on transients from other equipment ahead of the amplifieralways turn the amplifier on after other equipment has stabilized. 3. Turn off the amplifier and unplug it from the AC mains before replacing the fuse, installing an input sensitivity jumper or changing the position of the Dual-Mono switch. 4. There are important differences between Dual and Bridge-Mono mode wiring (refer to Section 3.3.1). 5. Operate the amplifier with the correct fuse: a 5 amp, 250 volt, type MTH fuse for units configured for 200 volt or higher AC mains, and a 10 amp, 250 volt, type AB fuse for units configured for AC mains of less than 200 volts. 6. Be careful when driving a transformer-coupled device (such as an electrostatic loudspeaker) or other loads that appear as a low-frequency short circuit (less than 3 ohms) without a series isolating capacitor. Such operation may damage the load and needlessly activate the amplifiers V-I limiting. 7. Operate the amplifier with AC mains of no more than 10% above the selected line voltage and at the specified line frequency (50 to 400 Hz). 8. Never connect the output to a power supply output, battery or power main. This can cause electric shock and damage to the amplifier. 9. Do not expose the amplifier to corrosive chemicals such as soft drinks, lye, salt water, etc. 10. Do not tamper with the circuitry. Unauthorized circuit changes invalidate the warranty. 11. Do not short the ground lead of an output to the input signal ground or oscillations may result. 12. We recommend that you avoid using the amplifier with frequencies above 30 kHz.

Also see the power matrix. Note: Maximum average power per channel at 1 kHz with 0.1% or less THD.

Output Signal

Dual: Unbalanced, dual channel. Bridge-Mono: Balanced, single channel.
Dual mode (both channels driven): 305 watts into 4 ohms. 175 watts into 8 ohms. 100 watts into 16 ohms. Bridge-Mono mode: 610 watts into 8 ohms. 355 watts into 16 ohms.
Load Impedance: Rated for 16, 8 and 4 ohm use. Safe with all types of loads. Power Supply: 1 kilowatt transformer with computergrade filter capacitors storing over 48 joules of energy. Power Efficiency: See Figure 6.7. Power Requirements: Requires 50 to 400 Hz AC with

Page 18

Protection
Overall Protection: AC line fused. Thermal switch in AC line protects against overheating caused by insufficient ventilation. Controlled slew rate voltage amplifiers protect overall amplifier against RF burnouts. Input overload protection is furnished by internal resistance at inputs of amp. Amplifier Output Protection: Short, mismatch, and open circuit proof. Limiting is instantaneous with no flyback pulses, thumps, cutout, etc. No premature limiting on transients. Turn-On: Instantaneous, with minimum thumps and no program delay.

Construction

Dimensions: 19 inch (48.3 cm) standard rack mount width (EIA std. RS-310-B); 7 inch (17.8 cm) height; 10.5 inch (26.7 cm) depth behind front mounting surface; 0.625 inch depth in front of mounting surface. Weight: Net weight is 40 pounds, 11 ounces (18.5 kg); Shipping weight is 45 pounds, 0 ounces (20.3 kg). Finish: Carbide black front panel, splatter-coat black chassis and top cover. Chassis: All aluminum construction for maximum heat conduction and minimum weight. Heavy aluminum front panel is a single extrusion. Heat Sinking: Massive black-anodized heat sinks are thermally joined with the chassis, thereby utilizing the entire amplifier as a heat sink.
Crown specifications are guaranteed for three years.
In an effort to provide you with as much information as possible about the high power-producing capabilities of your amplifier, we have created the following Power Matrix. All specifications found in these tables are valid for 120 VAC, 60 Hz models and are guaranteed for three years. Some spaces in the tables are left blank because we do not provide this same guarantee for those conditionshowever, your amplifier will perform well under all conditions listed in the table.

Power Specifications

When measuring power, 0.1% THD appears to be the industry standard for distortion. One of the maximum average power columns shown in the power matrix is measured when THD rises to 0.1% so you can easily compare Crown specifications to those of other manufacturers. But this high level of distortion actually allows for some clipping which is undesirable. Full-bandwidth maximum average power measured at 0.05% THD provides more reasonable, non-clipped conditions. Crown provides this specification with the hope that other manufacturers will also start providing specifications that correspond to the way amplifiers are used in the real worldwithout a clipped input signal. Many manufacturers publish power specifications with a tolerance of 1 dB or worse. That means their amplifier can deviate more than 20% in output! A 100 watt amplifier would meet their specification if it only produced 79.4 watts. Other manufacturers qualify their specs by saying they are typical, subject to manufacturing tolerances, single channel driven or that they are specified with fuses bypassed. Each of these statements effectively removes any performance guarantee. We take a different approach at Crownour published specifications are guaranteed for three years. Further, because our in-house specs are more stringent than our published specs, every Crown amplifier will exceed its published specs. We believe you should get what you pay for.

Page 19

Zo (ohms)

100 FREQUENCY (Hz)

Fig. 6.2 Nominal Output Impedance

60 Zo (degrees) 30

1K FREQUENCY (Hz)
Fig. 6.3 Nominal Output Phase Angle (1 amp)
Fig. 6.4 Nominal Damping Factor (8 ohms) Page 20
15 Phase Shift (degrees) 30

16 ohms 8 ohms 4 ohms

Fig. 6.5 Nominal Phase Response (1 Watt)

80 dB 100

Fig. 6.6 Nominal Crosstalk (Channel 1 at 150 watts and Channel 2 at Maximum Output)

60% EFFICIENCY 50%

SINGLE CHANNEL DRIVEN BOTH CHANNELS DRIVEN
Fig. 6.7 Nominal Power Efficiency (120 VAC Mains and Both Channels Driven) Page 21

nV Hz 10

Line frequency harmonics plotted to the tenth order. The 150 watt output is indicated by the dot at the top of the extended dashed line. Spectrum total is equivalent to 1.3 microvolts input noise over a 20 Hz to 20 kHz bandwidth.
Fig. 6.8 Nominal Noise Spectrum

0 dB ohms

8 ohms ohms 3 0.FREQUENCY (Hz) 1K 10 K 8 ohms with Level Control at 12:K
Fig. 6.9 Nominal Frequency Response (16 ohms at 0.5 watts, 8 ohms at 1 watt and 4 ohms at 2 watts)

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7 Internal Settings
From the factory, your amplifier is configured for an input sensitivity of 26 dB gain. For the DC-300A II, this setting requires an input signal of 1.75 volts (2%) to drive the amplifier to full output. You may optionally configure the unit for an input sensitivity of 0.775 volts (0 dBm) for full rated output power. To change your amplifiers input sensitivity to 0.775 volts, the chassis of the unit must be opened. WARNING: Risk of electric shock! Turn off the amplifier and disconnect its power cord from the AC mains before opening the amplifier chassis. CAUTION: Only a qualified technician should attempt to change the amplifiers internal settings. or a technician in the field can activate the setting without voiding the warranty.
7.2 Changing the Input Sensitivity to 0.775 V
Before undertaking this procedure, please read all of Section 7.1 to help determine whether you need to alter the amplifiers input sensitivity. 1. Turn the amplifier off and disconnect it from the AC mains. 2. Place the amplifier upside down on a flat surface. Remove the front panel by unscrewing the eight phillips screws along the top and bottom of the front panel and the four phillips screws behind the rack ears. Pull the front panel straight out from the unit. 3. Remove the four phillips screws that hold the main circuit board to its shield plate. It will hinge forward from the bottom to expose both sides. 4. Solder #22 jumper wires at the locations labeled R158 and R258 on the main circuit board (see Figure 7.1). 5. Reassemble in reverse order of disassembly.

8.2 North American Service
Service may be obtained in one of two ways: from an authorized service center or from the factory. You may choose either. It is important that you have your copy of the bill of sale as your proof of purchase. 8.2.1 Service at a North American Service Center This method usually saves the most time and effort. Simply present your bill of sale along with the defective unit to an authorized service center to obtain service. They will handle the necessary paperwork and repair. Remember to transport the unit in the original factory pack. A list of authorized service centers in your area can be obtained from our Technical Support Group. 8.2.2 Factory Service To obtain factory service, fill out the service information page that follows and send it along with your proof of purchase and the defective unit to the Crown factory. For warranty service, we will pay for ground shipping both ways in the United States after receiving copies of the shipping receipts. Shipments should be

Crown Audio Division

Technical Support / Factory Service 57620 C.R. 105, Elkhart, Indiana 46517 U.S.A.
Telephone: 219-294-8200 800-342-6939 (North America,
Puerto Rico, and Virgin Islands only)
Facsimile: 219-294-8301 Fax Back: 219-293-9200 800-294-4094 (North America only) Internet:

http://www.crownintl.com

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Crown Factory Service Information
Shipping Address: Crown International, Inc., Factory Service, 57620 C.R. 105, Elkhart, Indiana 46517 Phone: 1-800-342-6939 or 1-219-294-8200 Fax: 1-219-294-8301 Owners Name: _________________________________________________________________________ Shipping Address: ______________________________________________________________________ Phone Number: _________________________________________________________________________ Model: ________________________ Serial Number: ______________ Purchase Date: ___________

NATURE OF PROBLEM

(Be sure to describe the conditions that existed when the problem occurred and what attempts were made to correct it.)
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