BASS BOOST CONTROLS
1)“CH 3&4 Bass Boost”: Found in the “Channel 3 & 4 Controls” section, this switch allows the user to activate a 6 dB boost centered at 48 Hz for channels 3 & 4. When the “CH 3&4 Bass Boost” is activated, the inputs to “CH 3 (Left)”
and “CH 4 (Right)” are summed to create a mono signal. The “Filter Mode” switch in the “Channel 3 & 4” section must be in the “LP” position for the bass boost to be functional.
2)“Remote Bass Port”: This port allows you to connect an optional remote boost knob (sold separately as JL Audio Model RBC-1) that can be mounted in the front of the vehicle. With the RBC-1 connected, the boost is no longer limited to 0 or +6 dB, allowing a variable range of 0 to +12 dB of boost to be selected.
Pre-OUTS
The G4500 incorporates a pass-through preamp output section, so that additional amplifiers can be easily added to the system. This pass-through pre-amp output can be configured two different ways using the switch labeled “Pre-Outs Input From”.
1)“1&2”: The preamp output delivers the same signal that is connected to the CH 1&2 Inputs. This mode is useful for feeding a subwoofer amplifier when the G4500 is being used to drive front and rear speaker systems. In this mode, the preamp output signal will depend only on the input signal level of CH 1&2, allowing Channels 3&4 to be faded without affecting the subwoofer level. If CH 1&2 is faded in this mode, the signal level of the preamp output will change accordingly.
2)“Sum”: When the G4500 is being used to drive front and rear speaker systems, this preamp output mode will deliver a summed front/rear stereo signal to a subwoofer amplifier, while permitting fading of the front and rear speaker systems from the source unit. This method prevents a loss of signal to the subwoofer amplifier when the system is faded to the front or the rear by the head unit.
Note: Any signal delay between the front and rear channels can result in a cancellation of signals within certain frequency ranges when using the “Sum” position. If you experience a loss of bass output in the “Sum” position, compared to the “1&2” position, you are likely dealing with a delayed signal in either the front or rear outputs of the source unit. If the front to rear delay is desirable for other reasons or if it cannot be defeated at the source unit, we recommend that you use the “1&2” position.
Note: In either mode, the preamp output signal is not affected by the “CH 3&4 Bass Boost” processing selected for the amplifier or by any crossover filter selected (if the input signal is full- range, the preamp output will be full-range).
Note: The signal level of the “Preamp Output” is
line-level (low voltage), regardless of the position selected in the G4500’s “Input Voltage” switch. An additional amplifier connected to these preamp outputs should have its input voltage switch set to the “Low” position.
Speaker OUTPUTS
The G4500’s speaker outputs are designed to accept 16 AWG - 8 AWG wire.
Each pair of the G4500’s channels are designed to deliver power into speaker loads equal to or greater than 2 ohms per channel when using a “stereo” configuration and speaker loads equal to or greater than 4 ohms per bridged pair of
channels when using a “bridged” configuration.
Speaker loads below 2 ohms nominal per channel are not recommended and may cause the amplifier to initiate a protection mode which reduces power output.
Bridging Considerations Bridging is the practice of combining the
output of two amplifier channels to drive a single load. When bridged, each channel produces signals of equal magnitude, but opposite polarity. The combined output of the two channels provides twice the output voltage available from a single channel. The G4500 has been designed for bridging of its channel pairs without the need for input inversion adaptors.
To bridge a pair of channels, use the
“Left +” and “Right –”speaker connectors only (the “Left –”and “Right +” remain unused). When bridged, each channel will deliver optimum power into a 4 ohm load.
When a pair of channels are bridged, they will deliver 250W x 1 into a 4 ohm load or 160W x 1 into an 8 ohm load. Operating a pair of bridged channels into a load lower than 4 ohms is not recommended.
Because a bridged pair of channels requires that both channels receive input, you need to connect both left and right inputs to the source unit. Connection of only one input will result in reduced power output, increased distortion and can cause the amplifier to overheat.
Do not do this!
When a pair of the G4500’s channels are operating in bridged mode, the output will be in mono (only one channel). This mono channel can contain right channel only information, left channel only information or the sum of the information from both the right and left channels. In order to achieve one of these options, configure the inputs to that pair of channels in one of these two ways:
1)Left Channel Only or Right Channel Only Information: If you wish to send a left-only or right-only signal to a pair of the G4500’s channels, use a “Y-Adaptor” to split the single channel signal into both left and right RCA inputs. This option is useful when using a pair of the G4500’s channels to drive left channel speakers only and the other pair of the G4500’s channels to drive right channel speakers only.
2)Left + Right Channel Information:
When bridged and fed by a stereo input, a pair of the G4500’s channels will automatically combine the left and right channels into a summed mono (left + right) channel. This option is useful when using a pair of the G4500’s channels to drive a subwoofer system or a summed mono center channel.
