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MB Quart RA640.4

640W 4-Channel Reference Series Bridgeable Power Amplifier (RA6404)

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List price $259.99

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$99.95

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General Features:

  • Reference Series 4-Channel Class SQ Car Amplifier
  • Max Power Rating:
    • 4 ohms: 80 watts x 4 chan.
    • 2 ohms: 160 watts x 4 chan.
    • Bridged, 4 ohms: 320 watts x 2 chan.
  • FLUID-FETS MOSFET Circuit maximizing power efficiency while improving sound quality
  • LED power (green) and protect (red) indicators
  • Variable Bass Boost (0 to +12 dB bass boost)
  • Built-in system diagnostics and top-mounted controls
  • 4/3/2/1 Channel operation
  • Preamp RCA outputs to daisy chain multiple amps
  • 3-way protection circuitry (thermal, overload, and speaker short protection)
  • Black reference aluminum alloy heat-sink with illuminated MB Quart design
  • Input sensitivity:
    • Level: 200mV-6V
  • Variable high-pass filter (60-13,000 Hz)
  • Variable low-pass filter (30-250 Hz)
  • Frequency response: 30-45,000 Hz
  • 4 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: 8-1/4"W x 15-1/2"D x 2-3/8"H
  • Authorized Internet Dealer
  • 1-year Manufacturer's Warranty

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
RMS Power @ 2 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 2 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.

160 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.

320 watts x 2 channels

Amplifier Specifications

Amplifier Series
This designates the series of the amplifier. Many amps are available in a litany of different wattage and channel configurations, but maintain consistent features throughout the product line.
Reference (MB Quart)
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.

SQ
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.
4
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.

640 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.
4 AWG
Minimum Impedance Unbridged
The lowest impedance the amplifier will handle when it is not bridged.
2 ohms
Minimum Impedance Bridged
The lowest impedance the amplifier will handle when it is bridged.
4 ohms
THD at Rated RMS Power
The amount of change in harmonic content of the signal as it is amplified. A lower figure indicates less change and a more accurate amp. THD below 0.10% is inaudible.
0.05%
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.
No
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.
No
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.

Low-pass (LP)
High-pass (HP)
High-Pass Crossover Frequency
The high-pass crossover frequency can be a fixed crossover point or a variable crossover range. A variable high-pass crossover allows you to select a specific crossover point which allows frequencies above the set crossover point to pass, while making frequencies below the set point gently or harshly roll-off, depending on the steepness of the slope.

The steepness of the roll-off slope is measured in dB/octave and refers to the rate of attenuation (lowering of volume) outside their pass bands.

60 - 13000 Hz
Low-Pass Crossover Frequency
The low-pass crossover frequency is typically used for subwoofers. It can be a fixed crossover point or a variable crossover range. A variable low-pass crossover allows you to select a specific crossover point which allows frequencies below the set crossover point to pass, while making frequencies above the set point gently or harshly roll-off, depending on the steepness of the slope.

The steepness of the roll-off slope is measured in dB/octave and refers to the rate of attenuation (lowering of volume) outside their pass bands.

30 - 250 Hz
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.
92 dB
Channel Separation
Also referred to as crosstalk. The amount of interference on one stereo channel caused by the leaking of the other stereo channel. The higher the rating in decibels (dB), the better the Channel Separation.
80 dB
Bass Boost
The objective of the bass boost is to get more kick out of your subwoofer. It is a circuit that emphasizes the lower frequencies at a given point. The bass boost should always be set first before setting the gain. This feature is known for destroying subwoofers and is commonly used incorrectly, so be cautious.
0 - 12 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.
No
Fan Cooled
A great feature to have if an amp generates a large amount of heat. Cooling fans can help regulate the temperature to prevent the amp from overheating (burning).
No
Fuse Rating
The amperage and the number of fuse(s) an amp requires.
30A x 3 
Strappable
Some amplifiers can be "strapped" together in order to increase the output of a single audio channel. These amplifiers feature RCA preamp outputs, allowing you to pass the signal directly from one amp to the other to ensure consistency.
No
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.

No
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.

Warranty and Return Policy

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

Summary of Customer Ratings & Reviews

Rating Distribution

5 Star
78%
4 Star
11%
3 Star
0%
2 Star
11%
1 Star
0%

Average Attribution Rating

Durability
4.2
Value
4.8
Features
4.3
Design
4.3
Usability
4.7
Jonathan

Calera, AL

Overall
Durability
Value
Features
Design
Usability
info

December 11, 2014

great amp for the price. has the power to drive your speakers to loud levels with decent clarity. if you are on a budget this amp works. crossover setup doesn't work like regular crossovers so look into that to see if it will work for you

0 of 0 found this helpful

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Dan

Decatur, GA

Overall
Durability
Value
Features
Design
Usability
Good Deal: Loud with Good Sound Quality

December 4, 2014

I have had my RA640.4 powering a set of polk component speakers and infinity 6x9's for about a month now. All the speakers ask for about 90wrms at 2 ohms, each, and this amp does the job. In fact, it does the job better than my old infinity 4 channel amp (I think it was the 360.4) which is significantly pricier than this amp. Although I would say that this amp does not push 640 wrms, but hey, it is a little more powerful than the infinity and sounds just as good. Overall I would recommend this amp for anyone looking for a budget bang-for-your-buck amplifier.

0 of 0 found this helpful

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Vic

Orlando Florida

Overall
Durability
Value
Features
Design
Usability
Excellent sound Quality

February 7, 2014

If anyone have a question of how good is MbQuart RA640.4, I can honestly say It's excellent. I had JL 300/4 original and JBL Px300.4 and all I can say is, it sound if not the same, better than the JL. It kills the JBL. I replace the JL with JBL because it died after 8 year and I could tell the the sound quality went down, then I replaced the JBL Px300.4 one week ago with Mb Quarts RA640.4 and WAW incredible sound difference, it also took away some engine noise that I was getting with the Jbl. To be totally honest WAW, WAW, WAW and it does not get hot. " I have it under my car seat pushing 4 JL C-5s and could not be happier. I don't write reviews but this was an excemption. I was researching for over a month and I could not get a stright answer, so I hope this can help someone.

0 of 0 found this helpful

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Aaron

Saint Louis , MO

Overall
Durability
Value
Features
Design
Usability
Not what I expected from a "SQ" amp

December 16, 2013

I had this amp installed for a couple of weeks powering two sets of MB Quart QSD213's (the last handmade in Germany components sets from MB). I expected the reference amps to be in the same class as the prior equipment before Maxxsonics bought the MB Quart name. I was not impressed. From the plastic mounts and end caps to the cover that was drilled incorrectly, this amp felt as cheap as it is made. Clean power was not an option with this amp. Crossovers were still letting the low end through even after setting it higher than I usually would on other amps. I had Sonic cross-ship me a JBL 4 channel and the sound quality is in a different league than the RA640.4. I thought maybe my components were starting to show the wear and tear of 7 years of playing, but it was just a poorly designed amp that was the issue.

0 of 0 found this helpful

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Lc

Tacoma wa

Overall
Durability
Value
Features
Design
Usability
A real amp

October 12, 2013

This is the best buy I've ever had from sonic I'm telling you when I have a hertz energy setup in my car and this amp isn't even turned up a quarter of the way man this amp has some serious power and sound's clean to the bone and looks so nice.

0 of 0 found this helpful

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Kyle

Wooster, OH

Overall
Durability
Value
Features
Design
Usability
best amp for the price

September 18, 2013

It will be hard for one to find an amp that is as powerful as this one and as cheap. The best part is you are getting a quality amp. Everyone who knows me, knows that I buy what I want. If the amp i want is very expensive, ill wait and get it when i can. i wont settle for something else. So after doing my research and being content with buying a product that is cheap (which was a first for me in car audio) i am very pleased. For the money, you aren't taking a risk.

0 of 0 found this helpful

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Ryan

Tucson, AZ

Overall
Durability
Value
Features
Design
Usability
Great sounding amp

September 17, 2013

I'm running this amp pushing two sets of mb quarts 5 1/4 in a boat. It sounds great and gets loud, really loud

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Bill_ventura

Londonderry, NH

Overall
Durability
Value
Features
Design
Usability
Clarity, Power, Value. Concert in a Car...

August 26, 2013

Installed the MB Quart RA640.4 with 0 AWG and a 1.2F Cap and I am impressed!
I installed the amp in a '76 Ventura with 6x9" (Eclipse) in the rear deck and 6.5" (Alpine) in the kick panels.
The subtle parts of music don't get lost as the music becomes complex.
A friend asked if I had a subwoofer, because of the clarity and extension of the bass.
Thinking of buying another for my Silverado.
Great Amp for the $$$.

0 of 0 found this helpful

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Havolia

Snellville, GA

Overall
Durability
Value
Features
Design
Usability
Music to my ears!

May 16, 2013

Ordered amp, and it arrived two days later, installed that evening after I removed the Alpine MRP-F300 that was running my mids and highs, dont get me wrong, the Alpine was a great amp, just not strong enough for me. Got the MB up and running and WOW is all i can say,the clarity, the subtle details in the music, the warmth, and the power, this amp is rated 80W x 4 and I'm sure it's underrated, very clean and quite, midbass,midrange and highs soar with this amp, very very happy with purchase

0 of 0 found this helpful

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Accessory Tools and Products

Accessories added

NVX XKIT44 4-Gauge 4-Channel Wiring Kit

4-Channel 100% OFC Complete True 4 Gauge Amp Kit with RCA Cables and Speaker Wire

Your Price $99.99

NVX XBG3PK 1/0 Gauge OFC Big 3 Upgrade Kit

Comes with everything you need to upgrade your power and ground wire.

Your Price $59.99

Kicker Big 3 Package 1/0 Gauge Big 3 Upgrade Kit

Get all you need including wire cutters to upgrade your power and ground wire.

Your Price $151.99

Belva BBG3KT CCA 1/0 Gauge Big Three Kit

Features everything needed to upgrade factory power and ground wire.

Your Price $39.99

Small Universal Remote Level Bass Control

The Scosche RLC is a smaller universal bass remote that connects via RCA inputs.

Your Price $11.99

StreetWires FB4

4 AWG / 4 Gauge Firewall Bushing

Your Price $6.95

NVX XDBU4 - Top of the Line!

Distribution Block with Two 1/0 or 4 AWG Inputs and Four 4 or 8 AWG Outputs

Your Price $17.99

NVX XIV45 4-Channel RCA Audio Interconnect Cable

5 Meters (16.4 ft.) 4-Channel RCA Audio Interconnect Cable with Dual Twisted Pair Hyper-Flex Technology

Your Price $23.99

NVX XIX45 X-Series RCA Interconnect Cable

16.4 ft. of 4-Channel X-Series RCA Cable with Dual Twisted Pair Hyper-Flex Technology

Your Price $34.99

StreetWires ZN9 Series Interconnect Cable

16.4 ft. of 4-Channel RCA Cable with Rhodium-plated contacts and ZeroNoise construction for clear signal transfer!

Your Price $99.95

Kicker 4-Channel RCA Audio Interconnect Cable

4 Meters (13 ft.) 4-Channel K-Series RCA Audio Interconnect Cable

Your Price $19.95

NVX XWS1225 12 AWG Speaker Wire

25 ft. of True 12 Gauge 100% Copper EnvyFlex Speaker Cable/Wire

Your Price $39.99

NVX XWS1250 Speaker Wire

50 ft. of True 12 Gauge 100% Copper EnvyFlex Speaker Cable/Wire

Your Price $29.99

NVX XWS1625 16 AWG Speaker Wire

25 ft. of True 16 Gauge 100% Copper EnvyFlex Speaker Cable/Wire

Your Price $13.99

Belva BBSW167 16 AWG Speaker Wire

16 Gauge 7 Meter (23 Ft) Speaker Wire (CCA)

Your Price $12.99

Scosche SPL Meter SPL1000F

Handheld boomSTICK measures your SPL range from 60 to 135 dB

Your Price $21.99

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Product Summary

Manufacturer

Model Number

RA640.4

UPC

806576221067

Weight

9.00lbs

Internal SKU

ra6404

Internal Product ID

67883

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 RA640.4