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US Acoustics USX-4085

85W x 4 Car Amp

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  • US Acoustics USX-4085

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Item# 235USX4085
 
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Our take on the US Acoustics USX-4085

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.

Here's a reasonably-priced solution to the challenge of powering multiple sets of speakers with one amp. The USX4085 multi-channel amp from US acoustics is a rugged, terrific-sounding powerhouse that can drive a variety of speaker combinations. And built-in selectable high-/low-pass variable crossovers on its preamp outputs means you can add another amp, but you won't need to buy a separate component crossover.

Details:
  • 2-, 3-, 4-channel or Tri-Way output
  • 85 watts RMS x 4 at 4 ohms
  • 240 watts RMS x 2 in bridged mode
  • MOSFET output devices
  • 2-ohm stable in stereo
  • anti-thump circuit for quiet turn-on
  • thermal, short-circuit, and power/ground reversal protection
  • gold-plated differential preamp inputs to reject noise
  • MOSFET power supply
  • 12-200 Hz high-pass crossover (front and rear), 12 dB per octave
  • 40-200 Hz low-pass crossover (front and rear), 24 dB per octave
  • preamp outputs with selectable low-/high-pass crossover
  • THD at rated power 0.01 percent
  • 101 dB signal-to-noise ratio
  • 35 amp fuse
  • 17"W x 2-1/2"H x 9-5/8"D
  • 1-year warranty
 
 

Hands-on research from the Crutchfield Labs (what are the Labs?)

Features and Specs
Performance
RMS Power Output (Watts x Channels)
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85 x 4
Peak Power Output (Watts x Channels)
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N/A
Power at 2 Ohms (Watts x Channels)
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120 x 4
Bridged Power (Watts x Channels)
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240 x 2
Minimum Impedance Bridged
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4
Minimum Impedance Unbridged
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2
Best Frequency Response
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10-30k Hz
THD at Rated RMS Power
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0.01%
Signal to Noise Ratio
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101 dB
Input Voltage
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12.9v
Features
Amplifier Class
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AB
Low-Pass Crossover Frequency
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40-200 Hz
Low-Pass Slope (dB/octave)
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24 dB
High-Pass Crossover Frequency
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12-200 Hz
High-Pass Slope (dB/octave)
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12 dB
Bass Boost
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---
Bass Boost Frequency
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---
Fan Cooled
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No
Fuse Rating
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35
Speaker Level Inputs
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No
Preamp Outputs
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1 pair Gold RCA
Width (inches)
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17
Height (inches)
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2-1/2
Depth (inches)
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9-5/8
Parts Warranty
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1 YEAR
Labor Warranty
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1 YEAR
Product Research
What's in the box?

Download owner's manual

  • Blue amplifier with chrome trim and US Acoustics logo w/ a 35-amp blade fuse in chassis; 4 isolation plastic mounting feet; Manual; Warranty registration card with survey
  • NOTE: 4 self tapping screws (not included) are required for mounting

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 open the box, verify contents, 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.

Controls
Inputs/Outputs
Special Features
Specifications

Controls

Lowpass frequency control:  This controls the lowpass frequency for all of the channels set for lowpass operation using the mode buttons. It is variable from 40-200Hz with a 24 dB slope.

Mode buttons: The mode for channels 1 & 2 and channels 3 & 4 an be set to lowpass or flat/highpass. When a full range signal is desired this button is set to highpass/flat and the highpass frequency is set to the "flat" setting which allows all frequencies above 15Hz to pass through.

Highpass frequency:  This controls the highpass frequency for channels 1 & 2 and channesls  3 & 4. It is variable from flat to 200 Hz with a 12dB slope.

Gain control: There is a variable gain control for channels 1 & 2 and channels 3 & 4 from 110mV to 8.8V.

Selector switch: This is used to determine what is output through the RCA preamp outputs.  It may be set to "low", "1+2" or "3+4". When set to "low", the low pass crossover sets the low pass crossover frequency for the line outputs. Setting the switch to "1+2" allows you to set the RCA output high pass frequency with the channel 1+2 highpass selector (note that this can be set all the way down to flat if required). Selecting "3+4" allows you to set the RCA output high pass frequency with the channel 3+4 highpass selector (note that this can be set all the way down to flat).

Power: When the power is on a green power LED lights.

Protection: There is a red protection LED.

Inputs/Outputs

There is a gold plated terminal strip for +12V, remote and ground.

There is a gold plated terminal strip for left and right loudspeakers for channels 1/2 and 3/4.

RCA preamp outputs: There are gold plated stereo RCA outputs.

RCA preamp inputs: There are two pairs of gold plated stereo RCA inputs.

Special Features

The amplifier uses high current MOSFET devices.

There is a time delay turn-on with muting circuits.

The protection covers reverse polarity, thermal and short circuit.

The amplifier uses high speed, audio-grade components in all low level stages

Specifications

Power output is at 12.9V

RMS x 2 Ohms: 120 watts x 4

Channel separation: 81 dB

Best frequency response: 10Hz to 30kHz, -.5dB

Fuse: 35 amp blade

 
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