I connected the diminutive Stealth amp into my reference system, and drove my subwoofer with the rear channels and my reference speakers with the fronts. I like to use this test configuration on four channel amps because it will usually show any weaknesses in the amplifiers power supply. When an amp with a single power supply for all four channels is tested like this and asked to deliver high current to the woofer load, if its internal power supply isn’t stout enough it can cause audible distortion in the front channels when the bass hits. After getting the crossovers set to 50Hz high pass on the front channels, and 80Hz low pass on the bridged rears,
I sat down to do some listening.
Given the small footprint and relatively light weight (it only weighs about 4.5 pounds) my expectations were only, shall we say, moderate. Beginning with an audiophile recording of some of Manhattan Transfers biggest hits, I was pleased with the musicality and natural sound produced by the Stealth 440.4. Some full range Class D amplifiers I have auditioned have tended to add a bit of “bite” or harshness to horn sections, and occasionally they tend to be a bit sibilant especially with female vocals, and cymbals. None of that was found in the Cerwin-Vega Mobile amp, which added some credence to Mr. Morris’ comments about the tweaking they’d done. Moving on to some rock tunes from Rush, Deep Purple, Pink Floyd and Supertramp, I noted the amps ability to produce tight, controlled bass while still providing a nice articulate top end from the front channels. Pushing the volume higher, I eventually reached the amplifiers limits, but at volume levels much greater than I had expected when I began testing. The general sonic performance of the amp was good, with a level of transparency generally uncommon to the topology. I drove the amp pretty hard on all kinds of music for a couple of hours and the heatsink was barely warm to the touch, indicating the amp did indeed have exceptional efficiency. My only minor niggle was the incredibly bright blue power LED. It’s so bright, it’s almost distracting, but that will be of no consequence when the amp is in your trunk!
After the listening was concluded, the amp was moved into the electronics lab and its performance data carefully measured. The amplifier either met or exceeded all of the specifications provided in the owner’s manual. As it turned out, I was right about the amp being very efficient. Where a conventional 4 channel Class AB amplifier will struggle to be even 25% efficient at 10 watts of power per channel, the Stealth 440.4 was a very impressive 62%! And full power efficiency was good too, at 78% when driven into 4 ohms. The amp is quiet too, with a signal to noise ratio of over -78dBA at 2 volts of output, or over 97dBA referenced to full power.
Frequency response was flat as well, within 1.0dB from 20Hz to over 20kHz. And just for giggles I checked on the left to right gain tracking as well as the crossover slopes Mr. Morris had mentioned… they had indeed paid attention to it. The difference between left and right channels was within an inaudible 0.5dB at any gain setting, and the crossovers were indeed true -12dB/Oct filters.
CONCLUSIONThere was a time when I regarded the Cerwin-Vega Mobile products as sort of “brute-force” type of gear, which definitely has a place with a lot of enthusiasts. But with the advent of this new Stealth series, the company has proven they are capable of turning out some really high tech, good sounding products as well. If you’ve been thinking about a small footprint amplifier that can be hidden away easily, draws very little current, and sounds good, find a Cerwin-Vega Mobile dealer, and check out these new Stealth amplifiers. www.cerwinvegamobile.com