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

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.

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
A third problem to avoid is hum. The two most common sources of hum in an audio system are inductive coupling and ground loops. Inductive coupling can occur when input cables are subjected to a magnetic field from a power cord or power transformer. One way to prevent inductive coupling is to lace the input cables together along their length and route them as far away as possible from power transformers and power cords. The use of shielded pair cable is another effective way to reduce or eliminate hum resulting from inductive coupling. Ground loops often result when two or more devices are improperly grounded. This causes undesirable stray currents that may produce hum in the output. The best way to avoid ground loops is to ensure that all system devices are plugged into the same power strip. In addition, make sure that all cable shields are grounded at one end only. Input and output grounds are sometimes tied together for testing or metering. This can cause feedback oscillation from load current in the test loop. In some systems, even the AC power line may provide this feedback path. Proper grounding, input isolation and isolation of common AC devices in the system is good practice.

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.

Littlefuse 361000 series. If the loudspeaker is only susceptible to damage caused by prolonged overload (such as overheating), use a fuse or circuit breaker having the same slow thermal response as the loudspeaker itself (such as a slow-blow fuse). The nomograph in Figure 3.9 shows fuse size versus loudspeaker peak power rating. It can be used to determine the size of the required fuse.

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.

4.2 Indicators

Your amplifier has three front panel indicators. The yellow power indicator glows when the amplifier is turned on and the unit is receiving power. The IOC (Input/Output Comparator) indicators work like sensitive distortion meters. Each channel has a red LED (light emitting diode) that flashes when distortion of any kind exceeds 0.05%. They typically glow for about one minute after the AC power is turned off.

4.3 Controls

A power switch and level controls are located on the front panel. When you power up the amplifier, remember that the unit does not have a turn-on delay. Each channel has its own level control which is used to adjust the desired output level. Both level controls are used in Dual mode, but only the channel 1 control should be used in Bridge-Mono mode. The amplifier is switched between Dual and BridgeMono operation with the Dual-Mono switch located on the back panel of the amplifier (see Section 2). The units input gain is 26 dB as determined by 1% precision resistors in the feedback loop. This can be changed to a sensitivity of 0.775 volts by following the instructions in Section 7.

4.4 Protection

Your amplifier is protected against all the common hazards that plague high-power amplifiers, including shorted, open and mismatched loads; overloaded power supplies, chain destruction phenomena, input overload and high-frequency blowups. Protection against shorted and low impedance loads is provided by the JTS (Junction Temperature Simulation) circuitry. This circuitry instantaneously limits the amplifiers output voltage to the maximum safe level for the output transistors. With a loudspeaker, you can tell the amplifier has activated load protection because it causes audible distortion. The noise might be compared to crossover notch distortion or a snapping sound, depending on the load characteristics. Loudspeaker systems with impedances of 4 ohms or higher will not activate this system. All voltage amplification circuitry is designed to limit current. So in the extremely unlikely event of a device failure, the amplifier will prevent further damage.

Page 15

The input stages are protected from overload by series resistors. The unit also features a controlled slew rate and the JTS limiter that protect the amplifier from highfrequency blowups. A thermal switch is mounted on each heat sink to protect your amplifier against overheating. If either heat sink becomes too hot, the AC mains power will be interrupted until the temperature falls to a safe level and the unit resets itself. If the unit overheats, it will not produce any output and it will be very warm to touch.
turn off the power switch and disconnect the power plug from the AC mains. Unscrew the cap of the fuse holder and remove the fuse. CAUTION: The fuse holder has power even when the power switch is turned off. Always disconnect AC power before replacing fuses. Replace the fuse with a 10 amp, 250 volt, type AB fuse for units operating with an AC mains voltage less than 200 volts, or a 5 amp, 250 volt, type MTH fuse for units operating with an AC mains voltage of 200 volts or more. Reassemble in reverse order. WARNING: Never replace the original fuse with one rated for higher current (amperage).

Page 17

6 Specifications
Note: The following specifications apply to units configured for 120 VAC, 60 Hz operation in Dual mode with 8 ohm loads and an input sensitivity of 26 dB gain unless otherwise specified.
selectable transformer taps for 100, 120, 200, 220 and 240 VAC (10%) operation. Draws 40 watts or less at idle and 500 watts at rated power.

Performance

Frequency Response: 0.1 dB from DC to 20 kHz at 1 watt (see Figure 6.9). Phase Response: +0/15 degrees from DC to 20 kHz at 1 watt (see Figure 6.5). Signal-to-Noise Ratio: (20 Hz to 20 kHz) At least 110 dB below rated maximum average power (see Figure 6.8). Harmonic Distortion (THD): Less than 0.001% from 20 to 400 Hz and increasing linearly to 0.05% at 20 kHz at rated maximum average power. Intermodulation Distortion (IMD): (SMPTE-IM 60 Hz and 7 kHz) Less than 0.05% from 0.01 to 0.25 watts, and less than 0.01% from 0.25 to rated maximum average power. Damping Factor: Greater than 750 from DC to 400 Hz (see Figure 6.4). Crosstalk: See Figure 6.6. Slew Rate: Greater than 8 volts per microsecond. Voltage Gain: (At maximum output) 20.6:1 2% or 26.3 dB 0.2 dB. (Refer to Section 7 for information on the 0.775 volt sensitivity setting.)

Controls

Independent level controls and power switch are located on the front panel. Non-interacting DC balance controls are mounted on main PC board under electronics cover. A Dual-Mono switch is located below the input jacks on the back panel.

Indicators

Power: This yellow indicator remains lit while the amplifier is turned on.
IOC: These red indicators are normally off. They flash in the unlikely event of the output waveform differing from the input by 0.05% or more. They act as sensitive distortion indicators providing proof of performance.

Input/Output

Input Impedance: Nominally 25 K ohm. Input Sensitivity: 1.75 volts 2% for 310 watts into 16 ohms. Input: inch unbalanced phone jacks. Output: Color coded binding posts (banana jacks). Output Impedance: Less than 7 milliohms in series with less than 3 microhenries. See Figure 6.2.
Also see the power matrix. Note: Maximum average power per channel at 1 kHz with 0.1% or less THD.

Output Signal

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)

Page 22

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.

H10 R112

R101 R114
7.dB Gain vs. 0.775 V Input Sensitivity
For most applications, the amplifiers default setting of 26 dB gain will be ideal. At 26 dB gain, full output is achieved with an input signal of 1.75 volts. But some systems require their gain structures to be calculated based on a 0.775 volt sensitivity, while others cannot deliver the voltage required to achieve full output. In these situations, your amplifiers 0.775 volt input sensitivity setting offers a solution. A Crown Service Center

D100 R109

C4 W19

R146 R22 R246

Q201 C203

D112 R113

R102 U100

D113 R157

W32 W23

C109 D106

R123 C114

W10 D104 D105 Z7

R250 C220 R247 R222

Q104 R106 R10

R218 D201 D203 R206

C119 W2

R220 H5 R223

Q202 W13 R210 C205

C111 Z4 R213 W6

R127 R122

R212 R24 Q121 Q119 Q103

L200 C213

R228 R229

R156 R126 L100

R252 C118 R254 D108

R26 R256 R215 R25 C218

R217 R216

Z6 Z99

Z5 Q205 W14

C221 R225

C121 R125 R130
Fig. 7.1 Main Circuit Board (Component Side) and Input Sensitivity Jumper Locations Page 23

8 Service

This unit has very sophisticated circuitry which should only be serviced by a fully trained technician. This is one reason why each unit bears the following label: CAUTION: To prevent electric shock, do not remove covers. No user serviceable parts inside. Refer servicing to a qualified technician. sent UPS ground. (If the unit is under warranty, you may send it C.O.D. for the cost of freight via UPS ground.) The factory will return it via UPS ground. Please contact us if other arrangements are required.
Always use the original factory pack to transport the unit.

8.1 Worldwide Service

Service may be obtained from an authorized service center. (Contact your local Crown/Amcron representative or our office for a list of authorized service centers.) To obtain service, simply present the bill of sale as proof of purchase along with the defective unit to an authorized service center. They will handle the necessary paperwork and repair. Remember to transport your unit in the original factory pack. We will pay the surface shipping costs both ways for warranty service to the authorized service center nearest you after receiving copies of all shipping receipts. You must bear the expense of all taxes, duties, and customs fees when transporting the unit. Factory Service Shipping Instructions: 1. When sending a Crown product to the factory for service, be sure to fill out the service information form that follows and enclose it inside your units shipping pack. Do not send the service information form separately. 2. To ensure the safe transportation of your unit to the factory, ship it in an original factory packing container. If you dont have one, call or write Crowns Parts Department. With the exception of polyurethane or wooden crates, any other packing material will not be sufficient to withstand the stress of shipping. Do not use loose, small size packing materials. 3. Do not ship the unit in any kind of cabinet (wood or metal). Ignoring this warning may result in extensive damage to the unit and the cabinet. Accessories are not neededdo not send the instruction manual, cables and other hardware. If you have any questions, please call or write the Crown Technical Support Group.

Other equipment in your system: __________________________________________________________
If warranty has expired, payment will be: Cash/Check
Card Number:___________________________ Signature:_____________________________ Exp. Date:_______

MasterCard

C.O.D.
ENCLOSE THIS PORTION WITH THE UNIT. DO NOT MAIL SEPARATELY.

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