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
- 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
- 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
- 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.
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