AMPLIFIERS
Arc Audio KAR 400.4
By Paul Sonada
Posted on Thursday, Sep 16, 2004

Arc Audio’s first product showing was at the 1998 Consumer Electronics Show in Las Vegas. Based out of Modesto, CA, ARC Audio began with “a passion for excellence in the reproduction of music.” Headed by Robert Zeff, one of the brain trusts behind the original Zapco amplifiers, ARC Audio has set out to build high-end amplifiers for passionate audiophiles. The ARC Audio KAR 400.4 is an example of their latest work.

First Look
The ARC Audio KAR 400.4 is a Class AB, 4-channel amplifier housed in a sleek, clear anodized aluminum chassis. The understated style looks classy and refined. The front two channels include a 12 dB-per-octave, fully-variable crossover from 55 Hz to 550 Hz. The front channels also include a 45 Hz bass boost that allows up to 18 dB of maximum boost. The rear channels include a 12 dB-per-octave, fully-variable crossover from 55 Hz to 5500 Hz via a “x10” frequency multiplier. The RCA connections and signal adjustments are located on one side of the ARC Audio KAR 400.4, while the power and speaker connections, along with the 40 amp fuse, are located on the other side. The gold-plated power and speaker screw terminal connections can easily accept either bare wire or fork terminals.

A Closer Look
What you can’t see in pictures is how solid and sturdy this amplifier feels — all of the connections are positive, all of the controls feel precise.

For those who are familiar with amplifiers, the ARC Audio 400.4 may seem a little different. Typical amplifiers generally assign the front channels for midrange and tweeters and the rear channels for subwoofers. In the KAR 400.4, it’s exactly opposite. When looking at connecting the amplifier, this makes sense. I generally hook up the midrange and tweeter first (the rear channels are on the bottom level of connections) and tune them. Next, I add the subwoofer and blend them with the midrange and tweeter. The different configuration of the KAR 400.4 made this easier.

Another nice feature is the ability to bridge the front channels to the right RCA and the rear channels to the left RCA. This make it easy to transform the KAR 400.4 into an extremely powerful two-channel amplifier for satellite speakers.

Installation
The installation of the ARC Audio KAR 400.4 is simple. The metal mounting tabs are solid and placed at the four corners of the amplifier. The connections are well marked and easy to use. The ARC Audio KAR 400.4 gives you the right amount of controls to extract the best sound from the amplifier. If you’re unsure about your installation capabilities, it’s recommended that you have an authorized ARC Audio Dealer perform the installation.

Manuals/Web Support
The manual for the ARC Audio KAR 400.4 covered the family of two- and four-channel amplifiers. The manual was understandable and offered several system configurations for each type of amplifier. The sections on setting up the amplifier and trouble shooting should be a help to a DIY installer. The Web site, www.arcaudio.com, is easy to navigate. I was able to quickly find information about the ARC Audio KAR 400.4 amplifier. Basic specification and features are listed but there was no owner’s manual available for download at the time of writing this article.

Sound Q & Performance
This amplifier performs as well as it looks. On the test bench, the ARC Audio KAR 400.4 delivered 70.2 watts x 4 into 4-ohms with less than 1% distortion. Into 2-ohms, the KAR 400.4 delivered 107.5 watts per channel into four channels. This KAR 400.4 exceeded is rated power around 40 percent — very impressive. Into 4-ohms bridged, the KAR 400.4 delivered a respectable 248.5 watts per channel into two channels for a total amplifier power of 497 watts. At peak power, the ARC Audio KAR 400.4 average slightly above 70 percent, efficiency drawing 27.8 amps at 4 ohms stereo and 47.7amps at 4 ohms bridged. At one-third power, the amplifier’s efficiency dropped to 32 percent. This level of efficiency is typical of a Class AB design.

Only in one category did the ARC Audio fall short of its rated performance. Using the CEA-2006 standards, I measured the signal-to-noise ratio at 92 dBA. This was 3 dB shy of its rated 95 dBA.
When auditioning the ARC Audio KAR 400.4, the sound was smooth, detailed, and crystal. There were no audible noises during turn-on or turn-off. On bass tracks, the KAR 400.4 delivered good impact and control. While the amplifier did run warm, never did the KAR 400.4 sound strained or thermal.

Summary
The ARC Audio KAR 400.4 is a solid performer. This amplifier has enough power and is flexible enough to drive your complete system. Or, you could use it as the beginning to a high-power, high end system of sonic goodness. If you’re looking for a great sounding amplifier with the ability to grow, the ARC Audio 400.4 would be an excellent choice.