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MB Quart NA1-320.4

320W Ultra-Compact 4 Channel NA Series Full Range Class D Powersports Amplifier


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This item has been discontinued

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MB Quart NA2-320.4

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MB Quart NA1-320.4

320W Ultra-Compact 4 Channel NA Series Full Range Class D Powersports Amplifier


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StreetWires ZN7 RCA Interconnect Cable

16.4 ft. of 4-Channel RCA Cable with hyper twist construction, oxygen free copper, and precision machined tips.


Car/Marine Audio Installation Kit

Includes Test Light, Crimp/Splice Tool, Multi-bit Screwdriver and more.



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General Features:

  • NA Series 4-Channel Marine Amplifier
  • RMS Power Rating:
    • 4 ohms: 80 watts x 4 chan.
  • Full Range Class D Circuit Topology
  • Designed for - but not limited to - off-road vehicles
  • Perfect for discreet in-car installs
  • Nickel-plated RCA connections
  • Quick disconnect power and speaker cable connections
  • Selectable crossover modes: HPF / FULL
  • Frequency Response: 20-20,000 Hz
  • Signal to Noise Ratio: 90dB
  • Fuse Rating: 20A x 1
  • 10 gauge power and ground wiring is required for installation
    • Contact us for information regarding a discount on select amplifier kits from our website when purchased together with this amplifier
  • Dimensions: 3.7"W x 5.5"L x 1.7"H
  • Authorized Internet Dealer
  • 1-year Manufacturer's Warranty

Product History:

(newest, current model)
MB Quart NA1-320.4 thumbnail
(previous model, replaced by MB Quart NA2-320.4)

Power Specifications - Full Range Channels

RMS Power @ 4 ohms

The RMS power rating is the measure of continuous power that an amplifier can output, or a speaker can handle. It is the most accurate depiction of real, continuous power that the industry has so far.

If the final impedance of your speakers or subwoofers equals 4 ohms, this is how much power this amplifier will supply at that ohm level. The higher the RMS wattage, the more clean and loud your music will sound.

80 watts x 4 channels
Bridged RMS Power

Bridging refers to combining two channels on an amplifier to create one channel with double the voltage and an increased power output. A 2-channel amplifier will bridge down to 1-channel and a 4-channel amplifier can bridge to create 2-channels. An amplifier is most commonly bridged to drive a subwoofer.

Remember, once you bridge two channels down to one its final impedance will be 4 ohms unless otherwise specified. This rating lists the RMS power created once an amplifier is bridged.


Amplifier Specifications

Marine Certified
Marine certified means that the unit has been designed and manufactured with a marine use in mind. It will withstand the harsh conditions that come from marine use. Generally, they are treated against UV rays and treated with special protective coatings.
Amplifier Class

An amplifier increases the power of the signal being fed to it by taking energy from its power supply and matching the signal but increasing its amplitude. Amplifiers use many different methods for converting these electrical signals and have been categorized into classes.

Class A/B: Greater than 50% of the input signal is amplified while the other percentage is “off”. These amplifiers have a small amount of current flowing through the output transistors all the time which almost eliminates crossover distortion. Class A/B has great sound quality but is not as efficient as class D. These amps are most commonly used to drive speakers.

Class D: Also known as switching amplifiers, class D amps have output transistors that are completely turned “on” or “off”. This means that when the transistors are on, there is almost no voltage across them but when they are off there is significant voltage but no current flowing through it which makes these amplifiers very efficient at the cost of sound quality. These amps are most commonly used to drive subwoofers.

Other Classes: You may see classes such as GH, bD, X, FD, etc. by some manufactures. These amplifiers tend to be either class A/B, D or a hybrid of the two but with improvements to their designs that can make them more efficient or offer better sound quality.

Number of Channels
Each channel on an amplifier will power one speaker using a positive and negative cable. There are various types of amplifiers, each designed to power a certain number of speakers. Monoblock amplifiers, also known as single channel, are designed to power one or more subwoofers. These amplifiers often have very high power ratings. On the other hand, multi-channel amplifiers power multiple speakers, usually at lower power ratings. 2-Channel and 4-Channel amplifiers can power car speakers or low powered subwoofers. Occasionally you might see a 5 or 6-channel amplifier that can power speakers and subwoofers at the same time. The most common setup is a monoblock amp to run subwoofers and a 4-channel amp to run door speakers. Check out our Knowledge Base for more information.
Total RMS Power Output
Total RMS power is measured by multiplying RMS power per channel by the number of channels, and is calculated at the lowest level of operating impedance.

RMS power is the amount of continuous power, measured in watts, that an amplifier produces is called RMS power. The higher the RMS figure, the louder and cleaner your music sounds.

The RMS output figure is much more accurate than the peak rating when comparing products.

320 watts
Maximum Input Gauge Size
This is the largest gauge wire that will fit into the power and ground terminals of this device. The lower the gauge number, the thicker the wire is. For example, a 4 gauge wire is thicker than an 8 gauge wire and thus has higher current carrying capacity. Always do your best to get this size wire to reduce the risk of damage to your components.
10 AWG
Minimum Impedance Unbridged
The lowest impedance the amplifier will handle when it is not bridged.
4 ohms
Minimum Impedance Bridged
The lowest impedance the amplifier will handle when it is bridged.
Not Bridgeable
Speaker Level Inputs
Speaker level inputs are commonly referred to as high-level inputs and vice versa. This input type allows you to get your audio signal directly from the speaker wire in your vehicle, instead of using RCA cables. The advantage of this is factory integration, as most stock radios do not have RCA outputs to run amplifiers.
Preamp Outputs
Many amplifiers are equipped with RCA preamp outputs which pass the original music signal from the source to additional amplifiers. This is known as daisy chaining because the source connects to the first amp, and the first amp connects to the second amp, etc. The advantage to daisy chaining is you only need one 2-channel RCA cable to transfer the signal from the head-unit to the amplifier, and then one additional cable for each amp being daisy chained.
Built-in Crossover

A crossover is a type of filtering system that permits only certain frequencies to play. A Low-Pass (LP) crossover allows only frequencies below its setting to get through which is good in the case of some subwoofers. A High-Pass(HP) filter allows frequencies above its setting to pass through, this is normally used on speakers.

When a crossover is set to FULL it means no filtering is added and the full frequency spectrum is allowed through the amplifier. Filtering is important because feeding a speaker frequencies it cannot reproduce effectively creates distortion.

High-Pass (HP)
Full (AP)
Signal-to-Noise Ratio
This spec compares the strength of the signal to the level of background noise. A higher value indicates less background noise.
90 dB
Bass/Gain Remote
If the amp comes with a bass/gain remote you will be able to control the level of your bass from your dashboard. Typically bass remotes also include a 16-20 ft. wire for installation.
Fuse Rating
The amperage and the number of fuse(s) an amp requires.
20A x 1 
CEA-2006 Compliant
Amplifiers that have been tested to meet specific standards. When a car amplifier meets these standards, you can be sure that it will be able to produce the amount of power specified by the official CEA-2006 rating. Usually, these rating consist of the following items:
  • RMS Power
  • Signal-to-Noise Ratio

This rating applies to both external car amplifiers, as well as the amplifiers inside of in-dash stereos.

Sonic Certified Amplifier
Sonic Certified amplifiers have been tested by the experts at Sonic Electronix to meet or exceed the wattage ratings provided by the manufacturer. If this is marked as Yes, then you can trust the wattage ratings. If marked as No, then we have tested the amplifier and it did not meet the advertised wattage ratings. If marked as Not Tested, then the Sonic Electronix experts have not yet been able to test the amp.
Not Tested

Warranty and Return Policy

Parts Warranty Duration
1 year
Labor Warranty Duration
1 year
Warranty Provider

Summary of Customer Ratings & Reviews

Rating Distribution

5 Star
4 Star
3 Star
2 Star
1 Star

Average Attribution Rating


Wilmington Delaware

Nice amp

May 26, 2016

Nicely compact amp with plenty of power, highly recommend this amp for any biker!

0 of 0 found this helpful

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Accessory Tools and Products

Accessories added


Universal Bluetooth Audio Receiver & Volume/Playback Controller Knob

Your Price $74.99


Universal Bluetooth Audio Receiver

Your Price $74.99

StreetWires ZN7 RCA Interconnect Cable

16.4 ft. of 4-Channel RCA Cable with hyper twist construction, oxygen free copper, and precision machined tips.

Your Price $59.99

Car/Marine Audio Installation Kit

Includes Test Light, Crimp/Splice Tool, Multi-bit Screwdriver and more.

Your Price $20.99

Browse 3 questions and 8 answers
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Hi, I am looking for a 4 channel class D amp to augment my dual-din imported head unit. I am using Polk DB6501 and DB651 purchased from Sonic a couple of months ago. I don't want to run thick wires from the battery... I prefer to get a small amp and locate near the radio. I am thinking maybe the Alpine KTP-445U or MB Quart NA1-320.4 or the Dual DA704L. It seems all three of these options use power wire pigtails and could be powered by the same wires that supply the head unit. Does that seem right?
Eddy H on Aug 5, 2015
Best Answer: Hello Eddy,

-It seems all three of these options use power wire pigtails and could be powered by the same wires that supply the head unit.

That is not right, unfortunately. The thin wire that goes to a headunit is not a suitable gauge size to supply the amplifier with the power it needs to Make the power your require/expect. It would be the equivalent of giving You a stir straw to drink a milkshake. To take the NA1 as an example, review the manual linked below, it will show that it requires a direct connection to the battery. That is the only way an aftermarket amplifier will work properly.
Reply · Report · Rick MStaff on Aug 5, 2015
· Add Answer · I Have This Question Too (1)
Is this amp 2 ohm stable?
Mike P on Jun 11, 2016
Best Answer: If you're looking at the baby sized 320.4 then your question isn't valid. Unless you uncork it, void some warranties, and corrupt it with the soldering iron. You can't run it at 2 ohm. Which was a concern of mine, oooooh the dreaded forum fodder, might end up in mono. No. If you're looking to tuck something behind the dash, or splice into factory wiring. This is the bed I've ever dealt with.
Reply · Report · Dustin C on Jun 11, 2016
· Add Answer · I Have This Question Too (0)
what size stator/altenator is recommended for this amplifier?
how many amps does this amp draw
A shopper on Feb 21, 2017
Best Answer: It's low, not enough to dim the headlights, but more than a motorcycle can put out. I'd recommend at least an 85 amp alternator to accommodate the headunit, but it really depends on your total draw. Testify: It'll work in a UTV, and electric golf cart, besides my K5 Blazer. Best amp I've bought in 20 years of tinkering. Fits anywhere, with a good component set of speakers it punches above it's weight..
Reply · Report · Dustin C on Feb 21, 2017
· Add Answer · I Have This Question Too (0)

Product Summary


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Sonic Electronix Wiring Guide

Wiring Diagram Legend

Warning: The image depicted shows the resistance change when wiring multiple subwoofer terminals. Please refer to your subwoofer's owner's manual for the proper wiring of its terminals. Sonic Electronix, Inc. is not responsible for damage caused to your audio system or vehicle due to improper installation. Please call tech support at 1-877-289-7664 if you require additional assistance.

Product Name: MB Quart NA1-320.4