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The U.S. acoustics USB-4065 4-channel amplifier gives you high performance and value that can't be beat. You'll get the power (65 watts RMS x 4 channels) and clarity you crave (thanks to the high-current MOSFET power supplies and output stages), along with a budget-friendly price tag and a 3-year warranty. No other amplifier in this price range can boast that kind of warranty!

Wide-ranging, variable, high- and low-pass crossovers let you tune your system for optimal performance. You get sound that's custom-tailored just for you! Preamp outputs make it easy to add a second amplifier to your system, and an anti-thump circuit eliminates any annoying "thump" at power-up.


  • 65 watts RMS x 4 at 4 ohms
  • 80 watts RMS x 4 at 2 ohms
  • 160 watts RMS x 2 bridged output at 4 ohms
  • 2-, 3-, or 4-channel output
  • 4-ohm stable in bridged mode
  • Tri-way capable (Tri-Way crossover required)
  • requires 8-gauge power and ground leads — wiring and hardware not included with amplifier
  • variable high-pass crossovers (12-200 Hz, 12 dB/octave), front and rear channels
  • variable low-pass crossovers (40-200 Hz low-pass, 24 dB/ octave), front and rear channels
  • preamp outputs with crossover
  • anti-thump circuit
  • thermal, short-circuit, and power/ground reversal protection
  • 13-3/8"W x 2-5/8"H x 9-5/8"D
  • 3-year warranty

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

U.S. acoustics USB-4065 Reviews

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier with two 20-amp blade fuses inserted into the chassis
  • 2 Spare 20-amp blade fuses
  • 4 Plastic isolation mounting feet
  • 4 Self-tapping screws
  • 4 Flat washers
  • Owner's Manual
  • Warranty/Warranty Registration Card
  • Desiccant packet

Product Research

Inputs and Outputs Notes
Warranty Note


Power Supply and Output Devices: High-current MOSFET devices are used in the power supply and output stages of this amplifier.

Anti-thump Circuitry: There is a time delay turn-on with opto-coupled muting circuits for quiet, thump-free operation.

High-speed, Audio-grade Components: High-speed, audio-grade components are used in all low-level stages to help ensure signal integrity.

Mode Buttons: There is one mode button for channels 1+2, and there is a separate mode button for channels 3+4. Each button may be set for low-pass or flat/high-pass operation. When a full-range signal is desired for a pair of channels, the mode button for those channels should be set to the high-pass/flat position, and the high-pass frequency control should be set to "flat". When a mode button is in the high-pass/flat position and the high-pass frequency control is in the "flat" position, all frequencies above 15Hz are passed through to the speaker outputs.

Low-pass Crossover: A single dial controls the low-pass frequency for all of the channels set for low-pass operation using the mode buttons. The low-pass crossover control is variable from 40-200Hz with a 24dB/octave slope.

High-pass Crossovers: There are two high-pass frequency controls; one control is for channels 1+2, and the other control is for channels 3+4. The high-pass frequency controls are continuously variable from flat (full-range) to 200Hz; the high-pass crossovers have a 12dB/octave slope.

Preamp Outputs: The preamp output jacks provide a convenient source for daisy-chaining an additional amplifier without running an extra set of RCA cables from the front of the vehicle to the amplifier location. The position of the selector switch determines the type of signals sent through the RCA line outputs.  It may be set to "low", "1+2" or "3+4". When set to "low", the low-pass frequency control sets the low-pass crossover frequency for the line outputs. Setting the switch to "1+2" allows you to set the line output high-pass frequency with the channel 1+2 high-pass frequency control. Selecting "3+4" allows you to set the line output high-pass frequency with the channel 3+4 high-pass frequency control. Either high-pass selector may be set to "flat" for full-range output.

Protection Circuitry: Reverse polarity, thermal and short circuit protection circuits are used to help protect the amplifier from damage and ensure reliable operation.

LED Condition Indicators: A green power LED and a red protection LED are use to indicate the amp's operating status.

Inputs and Outputs Notes

Right Side of Amplifier:

  • +12V, Remote Turn-on and Ground Connections: gold-plated screw terminals; each terminal is 0.335" wide
  • Speakers Outputs: gold-plated screw terminals; each terminal is 0.335" wide

Warranty Note

Warranty Note: The Warranty Card states that the amplifier is covered by a 1-year parts and labor warranty if installed by an authorized U.S. acoustics installer, otherwise the warranty is 90 days. However, U.S. acoustics has extended a 3-year parts and labor warranty to all Crutchfield customers.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.