AudioSource amp three stereo power amplifier. (Equipment).

Manufacturer: AudioSource, 1327 North Carolan Avenue, Burlingame, CA 94010; 800/950-1449

Price: $550

Source: Manufacturer loan

Reviewer: Howard Ferstler

Anybody who has read a few of my product reviews and commentary opinions will probably conclude that I am not one of those people who become mesmerized when thinking of super-duper amplifiers or super-duper amplifier sound. For me, an amplifier is an appliance that will probably perform just as well 95% of the time if integrated into a receiver (in five-channel form, usually) as it would if mounted in a separate chassis and connected to a preamp via cables. Amplifiers are devices that are best heard and not seen, and it really does not make sense to romanticize the things.

Still, there is a lot to be said for powerful separate amplifiers for both stereo and multi-channel use. For one thing, if you have a truly upscale system that includes a sophisticated preamp or surround controller that is able to do things that few receiver control sections can do, you are going to need outboard amplification to make the installation work. For another, compared to most receivers, a preamp/amp combination simplifies the installation of certain kinds of outboard signal processors, like an equalizer. Outboard amplifiers definitely have their place.

The question is: does one need to invest megabucks in a super-duper version in order to get the job done, or will something more modest work just fine? In my opinion, the latter option wins hands down, and the AudioSource Amp Three proves my point. The one that was sent to me to review is a fine device that goes typical receiver amplifier sections one better. At the same time, it does not break the bank and steal money from one's record- or speaker-purchasing funds. On top of that, its modest price allows the owner to brag about what a great shopper he is, rather than spend time justifying to the skeptics, his wife, and even himself that he was not a sucker for having spent megabucks on something so mundane as a power amplifier.

The Amp Three is a 150 wpc (into 8 ohms), two-channel unit that can be bridged to deliver 400 watts mono. (There is a toggle switch on the back panel that allows you to opt for either the stereo or mono mode.) Input sensitivity to reach full output in the stereo mode is 0.8 volts, and the input impedance is 30 k Ohms. Total harmonic and intermodulation distortion are each said to be less than 0.04%, with a S/N ratio of 110 dB. The device is black in color, has dimensions of 16.5 x 4 x 13.25 inches (width, height, depth), and weighs in at liftable 28 pounds, 5 ounces. It has a detachable, three-prong power cord and a 5-amp fuse on the back panel. Line-level connections are gold plated, in the best high-end tradition. Those are the basics.

OK, the Amp Three, while pretty straightforward, has some extra features that will be of interest to some enthusiasts. For example, many power amps operate flat out with no gain controls, but the Amp Three has the option of allowing the user to adjust input sensitivity with a pair of knobs on the front panel. Under normal conditions, this would not be all that big a deal, and it is probably best to leave the two controls at the wide-open position and let the preamp handle level-adjustment chores. However, if you are using the unit in a multi-channel installation in company with some other power amps, the ability to adjust input sensitivity downward a tad might come in handy. In the bridged-mono mode, you use only the right-channel input and the right-channel level control handles the input gain.

Another interesting feature involves the ability of the unit to drive two pairs of speakers. This is controlled via the speaker A/B buttons on the front panel and the hookup for the task involves two pairs of five-way binding posts on the back. Most upscale power amps do not have such an option, and while some enthusiasts would never use more than one pair of outputs, anyway, it is a nice feature if you want to use the Amp Three to drive two pairs of speakers in two different rooms.

A third interesting feature involves the way you can power up the unit. If you want, you can turn it on and off in the typical manner, by means of the on/off button on the front panel. Or, you can leave the front-panel on button engaged all the time and plug the amp into a power strip that turns on the rest of your system at the same time as the amplifier. However, the device also has an auto mode (selectable via a rear-panel switch) that allows an input signal turn the unit on, much the same way that auto-on features work with a lot of powered subwoofers. This would be very handy if the amp was located some distance from the preamp (say across the room, between the speakers, and connected to the preamp by long, shielded cables), or if you were using it in its bridged mode to drive a heavy-duty, unpowered, non-electronically equalized subwoofer, such as one of the excellent units made by SVS. The circuit shuts the device off approximately ten minutes after input signals are no longer being input.

If I have any problems with this product, it involves the owner's manual that came with it. The information it contains about the amp is sketchy. For example, it says nothing about what kind of input impedance is involved with that 150 wpc rating (the company informed me about the 8-ohm impedance), and no mention at all is made of 4-ohm output abilities, other than to say that the unit can handle a load as low as 2 ohms. The headroom is said to be 2 dB, but that is rather vague in light of the missing data about 4-ohm load performance.

Also, the device has stereo line-level outputs that allow input signals to pass through after feeding the amp section, and I assume that they can be used if one wants to piggyback a second amp onto the first one. However, the notation about this feature in the manual makes no mention of this, and simply repeats a description of the line-in hookup. The AudioSource web site was nearly as uninformative and vague about the abilities of the entire product line as the manual was about the Amp Three. To be fair, though, I must reoport that the company has informed me that the owner's manual is in the process of being reprinted with more thorough information.

My tests of the Amp Three involved setting it up so that I could rapidly do A/B comparisons between it and the amp section of my old Yamaha DSP-A1000 integrated unit. The Yamaha had been indistinguishable from the amp sections in my newer DSP-A1 integrated unit, as well as from a Bryston 2B-LP unit that I had on hand when I did a series of comparisons with an ABX box that Tom Nousaine had loaned to me some time back. I also directly compared the Amp Three to an older AudioSource model, the Amp One, which, like the A1000, I use as part of my portable test rack.

In both comparisons (using a variety of musical source materials, as well as pink-noise test signals) I could not tell the Amp Three from either the Yamaha or the Amp One. Two different speaker pairs were used during this face off: Dunlavy Cantatas (see Issue 87) and NHT ST-4 units, which I was in the process of reviewing when I had the Amp Three on hand to also review. Wires were 14 AWG stranded.

Of course, the Amp Three has double the power of those other units, and I suppose if I had pushed playback levels to uncomfortable levels, it would have been possible to detect a difference. Indeed, it is under such conditions that one would consider it smart to pay for the extra power the unit provides. However, even in a 3400 cubic foot room, the three amps sounded identical (and I mean identical) at sane playback levels with a variety of musical source materials.

To my way of thinking, in addition to being an exemplary source of power in a killer two-channel system, the Amp Three would work quite well as a main amp in an upscale, multi-channel audio and audio/video system. You could use it to drive the front-main speakers, use the company's smaller Amp One/A in its bridged mode to drive the center channel, and use a second Amp One/A to power the two surround speakers. (Here, I am assuming that the Amp One/A works as well as my own, older Amp One unit.) If you had additional surround channels (a Lexicon or Meridian processor perform at their best with seven channels) you would use still another Amp One/A. And yes, the AudioSource units are fully compatible with those megabuck surround processors.

While some enthusiasts believe that the surround channels need as much power as the mains, in nearly all cases I have encountered, the surrounds can get away with somewhat less than what the mains require, even with DVD-A, DD, and DTS program sources. The five-channel combination I have noted will deliver 150 watts into 8 ohms with the left/right mains, 200 watts (bridged) to the center, and 80 watts each to the two surround channels. That should do the trick quite well in nearly any listening room that is not downright huge, or with speakers that have fairly normal sensitivities and are not too exotic in their load characteristics.

The upshot with a five-channel set up would be substantially powerful, first-class amplification for about $1,150 (list), which puts the AudioSource package into the same bang-for-buck category as the Outlaw 750 power amp reviewed in Issue 83 by David Doll, particularly when you remember that most retailers will also offer a discount with AudioSource products. Indeed, as a Sensible buy, I cannot think of any five-channel, separate-amp combination that beats the choices offered by those two companies.

Those shopping for a good, stereo power amp at a reasonable price would be hard pressed to top the Amp Three. It is a terrific performer that should be able to hold its own with just about any amp I can think of in its power category, including those that cost considerably more. Those in search of good amplification for five-, six-, or seven-channel audio-video system made up of separates, and for use in all but a huge A/V room, would be equally hard pressed to surpass the combinations I noted above, no matter how much they spent.

-HF