Features

Overview: JBL Marine amplifiers are designed to provide ample power to the speakers and subwoofers on your boat or 12-volt outdoor system. The amplifiers are equipped with conformal-coated circuit boards and other protections to withstand the harsh marine environment, where moisture and water spray may be prevalent. The MA4505 Class D 5-channel amplifier will accept both high-level and low-level inputs. The unit comes with spare fuses, speaker wire-to-RCA adapters, and corrosion-resistant stainless steel mounting hardware.

Power Output: The MA4505 delivers the following power output:

• Full Range Channels:
  • 45 watts RMS x 4 at 4 ohms (<1.0% THD+N)
  • 65 watts RMS x 4 at 2 ohms (<1.0% THD+N)
  • 130 watts RMS x 2 at 4 ohms bridged (<1.0% THD+N)
• Subwoofer Channel:
  • 320 watts RMS x 1 at 4 ohms (<1.0% THD+N)
  • 500 watts RMS x 1 at 2 ohms (<1.0% THD+N)

Protection Circuitry: The amplifier features protection circuitry for thermal overload, over- or under-voltage (<9V or >16V), and short circuits. The LED on the top of the amp glows red if the amp goes into protection mode.

Controls: The MA4505's controls are located on one side of the amplifier. The rotary controls require a small screwdriver (not included) to make adjustments. The amp controls include:

• Gain: The rotary gain controls let you match the amp's input sensitivity to the output of the source unit. There are separate gain controls for the front, rear, and subwoofer channels.
• Input Level: The Input Level switch lets you select the type of input you are using. For high-level input, there are two settings: Hi1 and Hi2. If the audio system fails to play with an amplifier connected to its output, or you get a "speaker disconnected" message on your factory stereo, set the switch to the Hi2 position. The Hi2 position includes a circuit design to fool this type of factory system into "seeing" a speaker connected to its output.
• Crossovers: The amp features switchable crossovers for the front and rear channels that can be set to low pass (LPF), high pass (HPF), or Full Range. The subwoofer channel has a non-defeatable low pass filter. You can adjust the cutoff frequency of the crossovers from 32Hz to 320Hz using the independent rotary controls.
• Bass Boost: You can apply up to 9 dB of bass boost, centered at 45 Hz, using the rotary control.
• Phase: You can switch the phase of the subwoofer from 0° to 180°.

Connections: The JBL Marine MA4505 uses set screw terminals for the +12V power, ground, turn-on (remote) lead, and speaker outputs. The screws can be tightened/loosened with a Phillips-head or flat-head screwdriver (not provided). The tops of the terminals are covered by a rubber plug to prevent water from entering the amplifier. The amp connections include:

• Power/Ground: The +12V Power and Ground terminals will accept up to 4-gauge wire. It is recommended that you use a minimum of 4 AWG power wire to the battery, with an in-line 100A fuse installed no more than 18" from the battery terminal. A 4 AWG ground wire (minimum) is also recommended, and attached to a metal area close to the amplifier.
• Remote Turn-On: The Remote terminal will accept up to 8 AWG wire. Typically, an 18 AWG turn-on lead is included in an amplifier wiring kit.
• Speaker Outputs: The amp features screw terminals that accept up to 8 AWG wire for connecting five speakers. There are markings on the terminals for bridging the amplifier.
• Speaker-Level Input: The amp includes four bare wire-to-RCA adapters for connecting the amp to a factory radio or aftermarket head unit without preamp outputs. You should attach each speaker wire from the head unit to an adapter and plug the adapter's RCA plug into the amp.
• Line-Level Inputs: The amplifier is equipped with three pairs of RCA inputs for connecting stereo RCA patch cables from the head unit to the amp.