About the JBL MA704
If you've ever tried to power your boat's speakers with a marine radio, then you know that you need serious power to get good sound out on the open water. Sporting a sleek stealthy profile, JBL's MA704 marine amplifier will deliver 70 watts RMS each of four separate speakers. The amp could also power two speakers and a sub, in 3-channel mode. For even louder fun, you could bridge the amp to 2-channel mode and power a couple high-performance speakers with 200 watts RMS each. And JBL uses a coated circuit board and stainless steel connectors to ensure that this amp will rock for many seasons to come.
Works with almost any system
Speaker-level inputs allow this amplifier to work in almost any system, even if you're keeping your boat's original radio. The separate high- and low-pass filters on the front and rear channels help maximize the performance of your speakers and subs.
MA704 input and control panel
- 4-channel marine amplifier
- 70 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
- 200 watts RMS x 2 at 4 ohms in bridged mode (4-ohm stable in bridged mode)
- Class D amp technology
- variable high- and low-pass filters (32-320 Hz, 12 dB/octave) on front and rear channels
- conformal-coated circuit board and stainless steel connections resist salt water corrosion
- preamp and speaker-level inputs
- high-level input adapter included
- preamp outputs
- fuse rating: 30A x 2
- wiring and hardware not included with amplifier
- 8-gauge marine-rated power and ground leads recommended
- dimensions: 14-11/16"W x 2-3/8"H x 7-5/16"D
- warranty: 1 year
- Our 60-day money-back guarantee
- MFR # MA704
What's in the box:
- 4-Channel Marine amplifier with two 30A ATO fuses installed
- 2 Spare 30A ATO fuses
- 4 Speaker wire-to-RCA adapters
- 4 Self-tapping screws (length 2")
- Quick Connect Guide
- 2 JBL decals
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More details on the JBL MA704
Features & specs
|RMS Power Output (Watts x Channels)||70 x 4|
|Frequency Response at Rated RMS Power||20-20k Hz|
|THD at Rated RMS Power||1%|
|Signal to Noise Ratio||85 dB|
|Peak Power Output (Watts x Channels)||---|
|Power at 2 Ohms (Watts x Channels)||100 x 4|
|Bridged Power (Watts x Channels)||200 x 2|
|Minimum Impedance Bridged||4|
|Minimum Impedance Unbridged||2|
|Low-Pass Crossover Frequency||32-320 Hz|
|Low-Pass Slope (dB/octave)||12 dB/octave|
|High-Pass Crossover Frequency||32-320 Hz|
|High-Pass Slope (dB/octave)||12 dB/octave|
|Bass Boost Frequency||N/A|
|Speaker Level Inputs||Yes|
|Preamp Outputs||1 pair|
|Parts Warranty||1 Year|
|Labor Warranty||1 Year|
Overview: JBL Marine amplifiers are designed to provide ample power to the speakers or 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 MA704 Class D 4-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 MA704 delivers the following power output:
- 70 watts RMS x 4 at 4 ohms (<1.0% THD+N)
- 100 watts RMS x 4 at 2 ohms (<1.0% THD+N)
- 200 watts RMS x 2 at 4 ohms bridged (<1.0% THD+N)
- 1000 watts x 1 peak
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 MA704'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 and rear 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.
- Crossover: The amp features switchable crossovers that can be set to low pass (LPF), high pass (HPF), or Full Range. You can adjust the cutoff frequency of the crossover from 32Hz to 320Hz using the rotary control. There are separate crossovers for the front and rear channels.
Connections: The JBL Marine MA704 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 8 AWG power wire to the battery, with an in-line 60A fuse installed no more than 18" from the battery terminal. An 8 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 for connecting four 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 two pairs of RCA inputs for connecting stereo RCA patch cables from the head unit to the amp.
- Pre-Out: A third pair of RCA jacks is provided to output the audio signal to a second amplifier, if desired.