Instruction Manual

ManualsBrandsCrown Audio ManualsReceivers and AmplifiersDC-300AII

DC-300A II Power Amplifier

Page 23

7 Internal Settings

From the factory, your amplifier is configured for an in-

put 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 con-

figure the unit for an input sensitivity of 0.775 volts (0

dBm) for full rated output power. To change your

amplifier’s input sensitivity to 0.775 volts, the chassis of

the unit must be opened.

WARNING: Risk of electric shock! Turn off the am-

plifier and disconnect its power cord from the AC

mains before opening the amplifier chassis.

CAUTION: Only a qualified technician should at-

tempt to change the amplifier’s internal settings.

7.1 26 dB Gain vs. 0.775 V Input Sensitivity

For most applications, the amplifier’s 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 amplifier’s 0.775 volt input sensi-

tivity setting offers a solution. A Crown Service Center

Fig. 7.1 Main Circuit Board (Component Side) and

Input Sensitivity Jumper Locations

H1 H2

H3H4

C200

C203

C205

C206

C208

C209

C210

C211

C212

C213

C214

C218

C219

C220

C221

C100

C103

C105

C106

C108

C109

C110

C111

C112C113

C114

C118

C119

C120

C121

L200

L202

L100

L102

Q200

Q201

Q202

Q203

Q204

Q205

Q206

Q207

Q219

Q220

Q221

Q100

Q101

Q102

Q103

Q104

Q105

Q106

Q107

Q119

Q120

Q121

X17

X14

X16

X24

X26

X27

R22

R24

R25

R26

R201

R202

R205

R206

R209

R210

R212

R213

R214

R215

R216

R217

R218

R219

R220

R221

R222

R223

R224

R225

R226

R227

R228

R229

R230

R246

R247

R250

R251

R253

R254

R256

R252

R152

R101

R102

R105

R106

R109

R110

R112

R113

R114

R115

R116

R117

R118

R119

R120

R121

R122

R123

R124

R125

R126

R127

R128

R129

R130

R146

R147

R150

R151

R153

R154

R156

W11

W12

W15

W16

W17

W18

W21

W22

W23

W24

W13

W14

W19

W20

W10

W26

W27

W28

W29 W31

W30

W32

H5 H6

H10

H11

Z99

R10

R157

R158

R257

R258

Z10

D200

D201

D202

D203

D204

D205

D206

D207

D208

D212

D213

D100

D101

D102

D103

D104

D105

D106

D107

D108

D112

D113

U200

U100

or a technician in the field can activate the setting with-

out 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 al-

ter the amplifier’s input sensitivity.

1. Turn the amplifier off and disconnect it from the

AC mains.

2. Place the amplifier upside down on a flat sur-

face. 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.