| From | IN4001 Diode | To |
| Source |
| |
| Unit | | Amp |
4.In some systems it may be desirable to have two sources play simultane- ously through the audio system. For instance, if you have a factory-installed radio in your car and you want to add an aftermarket CD player, you may connect the CD player to the RCA inputs of the amp and the factory radio to the Universal Interface speaker inputs. (Note: Front and rear channels of the CD and radio must be driven into the front and rear inputs of the amplifier. Use Y adapters if necessary.) The Universal Interface circuitry will isolate the two signals from each other while allowing them to drive the amp simultaneously. Therefore, switching from one source to the other is as sim- ple as turning the unused source off, and the other on. (Note: you must con- nect the remote turn-on wire from the CD player to the Rem terminal on the amp. Install a diode in the remote line from the CD player as shown in the diagram above.)
System Setup and Adjustment
Electronic Crossover
The electronic crossover in the P-4020 and P-4040 should be used to route the appro- priate signal to speakers intended to play only bass, or only midrange and treble fre- quencies. The crossover slope is 12dB/oct and the frequency is fixed at 80Hz.
Pre-amp Outputs
Connect these to the input connectors of other amplifiers or processors in your system. Refer to the “Applications” sec- tion for system expansion possibilities.
Setting Input Sensitivity
Proper input-sensitivity control settings on Power Series amplifiers are critical to ensure optimum performance, low noise levels and maximum system reliability. As a general rule, controls at the front end of a system (source, equalizers and other processors) should be set as high as possible with the amplifier input sensi- tivity set as low as possible while still providing adequate volume levels. Using a high signal level and a low-sensitivity setting will help keep background noise in the system to a minimum.
Initially, turn the input sensitivity GAIN control to its minimum (counterclock- wise) position.
1.Reconnect the (–) negative lead to your vehicle’s battery. Apply power to the audio system and play a favorite music track from CD or tape. (Note: After the source unit is on, the JBL badge (on the top panel) will illuminate, indicating the amplifier is on. If not, check the wiring, especially the remote connection from the source unit. Also refer to “Trouble- shooting” on page 7.)
2.On the source unit, increase the volume control until it is approximately 3/4 of its maximum output level. Slowly increase the Input Sensitivity control (clockwise) toward three o’clock and, at the same time, listen to the quality of the reproduced sound. At some point, you’ll hear distortion on the music peaks. Stop the adjustment and turn it back slightly. This is the maxi- mum undistorted output level of your system, and it should not be exceeded during use.
3.After adjusting the level of the main speakers in your system, you should adjust the remaining channels (if you are using a P-4040 or a multi-amp system) for the desired system bal- ance. You’ll find this easiest to do by adjusting the channels in the following order: 1) front speakers, 2) rear speak- ers, 3) subwoofer. Elaborate, multi- channel systems may be complex to adjust. Your local JBL installation spe- cialist is the best person to help with such an adjustment.
Applications
For your convenience, we’ve included several application diagrams to help you plan your own system installation. Figures 1 through 3 show how to config- ure the JBL P-4020 or P-4040 for stereo, bridged-mono and tri-mode operation. For system expansion ideas, see Figures 4 and 5 on the next page. (Note: For sim- plicity, Figures 1 through 5 do not show power, remote and input connections.)
Many different system configurations are possible using the crossovers and pre- amp outputs featured in Power Series amplifiers. If you are considering expand- ing your system beyond what is shown here, please consult your local JBL instal- lation specialist, who is experienced in designing complex mobile-audio systems.
