Power amplifiers are a necessary evil. The necessary part is obvious: without power amplifiers, speakers would be mute. The evil part comes from their weight, power inefficiency, and occasionally ungainly size and looks. Yes, there's a good reason why most power amplifiers spend their working lives ensconced in equipment racks.
Power amplifiers don't have to be hulking behemoths, though. One way to make power amplifiers smaller is to create a mono-block power amplifier that handles only one channel. Another way is to use the latest Bang and Olufsen digital ICEpower amplifier module, which B&O claims is more efficient than conventional power amplifier circuits. Wyred 4 Sound has employed both of these methods to create an eight-pound, single-channel power amplifier capable of producing 430 watts into four ohms that measures only eight inches square by 3.5 inches high. Although not quite juggle-able by your average audiophile, the $899 Wyred 4 Sound mAMP still qualifies as a very small-footprint amplifier capable of big sound.
Although the B&O ICEpower circuit serves as the heart of the mAMP, Wyred 4 Sound hasn't merely stuck a circuit board into a case. Wyred 4 Sound begins with the latest module from B&O and mates it with Wyred 4 Sound's "completely redesigned" input stage. This input circuit accepts both single-ended and balanced XLR inputs and includes a dual-differential common mode converter so that the mAMP can operate in pure balanced mode, whether the input signal is balanced or not. The input circuit also isolates the front end to eliminate input impedance mismatches between the mAMP and whatever is connected to it. The mAMP's input buffer has 100k impedance, which should make it "play nice" with virtually any preamp, tube or solid-state.
Wyred 4 Sound refers to the mAMP as "third-generation technology" that significantly reduces operating noise by using balanced circuitry, low-noise capacitors, and a quad-paralleled field effect transistor buffer. With a published specification of less than 125 uV and a 111dB dynamic range, the mAMP also offers slightly more gain than the standard 26 dB with 30.5 dB. For most systems, the extra 4.5 dB will be a welcome addition but, if you have any ground-loop hum issues or an especially noisy CD player or preamp, the mAMP will also make the noise slightly louder than would a conventional gain amplifier.
Installing the Wyred 4 Sound mAMP is no different than installing any other power amplifier. You have a choice of balanced XLR or single-ended RCA line-level input connections and a set of gold-plated five-way speaker binding posts for speaker connections. The rear of the mAMP also has a pair of 12-volt trigger connections, an IEC AC connection, an on/off switch, and a sliding universal voltage adjustment switch. For most of the review, I used the pair of mAMPs in my computer desktop system, where they mated successfully with a number of speakers, including the 89dB-efficient Golden Ear Aeon 2 and the 84dB-efficient Audience ClairAudient "The One" speakers. I also used Role Audio Canoes, ATC SCM7s, Silverline Minuet Supremes, and Ariel Acoustic 5Bs. Near the end of the review period, I installed the mAMPs in my two room systems, where they drove my Dunlavy Signature VIs, Genesis 6.1s and Skiing Ninja-modified AV123 X-Static speakers. I also used a variety of speaker cables, interconnects, and digital cables from Synergistic Research, AudioQuest, Kimber, Wireworld, and Transparent Audio.
Wyred 4 Sound touts the mAMP's energy efficiency. Its idle power consumption is only 9.5 watts and standby consumption less than 0.5 watts. However, the amplifier doesn't run as cool as the specifications suggest. After being in operation for more than 30 minutes, the mAMP produces more heat than some "high-efficiency" amplifiers. While never too hot to touch, the mAMP does get more than merely warm and should be installed so that it has some some air circulation around it.
Although the mAMP is small in overall size, the cabinet itself is quite robust. Machined from a solid piece of 0.75-inch-thick aluminum, the front panel has a "line-grained" texture with black anodizing. The mAMP's chassis is made of black powder-coated steel with top and side venting for heat dissipation. Although it only weighs eight pounds, if you drop an mAMP on your foot, you will not be a happy camper.
Read about the performance of the Wyred 4 Sound mAMP on Page 2.