Solid State Power Amp Reviews

Of the hundreds of product reviews I have written over the years, it is perhaps those of power amplifiers that present the hardest task in defining their worth. This is not because power amps are unimportant. As I wrote in my review of the MBL Corona C15 monoblock, in June 2014, "it is the power amplifier that is responsible for determining the character of the system's sound, because it is the amplifier that must directly interface with the loudspeakers. The relationship between amplifier and loudspeaker is complex, and the nature of that relationship literally sets the tone of the sound quality." But because the amplifier's role is so fundamental, it can at first be difficult to determine a given amp's balance of virtues and failings. A paradox.

We cannot recall when any new products have generated as much of a stir among perfectionists as the new solid-state equipment from Audio Research. Preceded by rumors of "a new kind of amplifying device—a cross between a tube and a transistor"—the announcement of ARC's new power amp and SP-4 preamplifier elicited very mixed reactions from loyal ARC customers, some of whom gleefully anticipated a virtual revolution in audio electronics, others of whom felt betrayed by the company which, having originally convinced them that "Tubes Are Better," suddenly seemed to be doing an about-face and espousing the views of the Enemy—the "Soiled-State"—forces.

Several seconds after I began listening to it, I knew that Theta Digital's Prometheus monoblock amplifier ($12,000/pair) was different from other amplifiers. The violins and brass were more dynamic, and had more pace. The orchestra sounded more three-dimensional, depicted in relief by a degree of hall ambience I hadn't heard when I played the same recording through my reference solid-state stereo amplifier, a Mark Levinson No.334.

Power amplifiers are unglamorous but essential. In theory, they have only one task. But, according to audio sage Yogi Berra, "in theory, theory and practice are the same. In practice, they are not." Amplifiers must take a voltage input signal and provide an output of somewhat higher voltage but of substantially higher current, the product of which is power. The task is complex in that this output must be applied to electrical interfaces whose characteristics vary widely from speaker to speaker—across the audioband and, for some, even at different power levels. There are no control mechanisms or feedback signals to help. The power amp must just stand and deliver.

Very few products exude opulence as do the Rowland amplifiers: the massive chassis, the gold finish, those sculpted handles on the front plate. For some strange reason the amp reminds me of Brutus Beefcake, the golden boy of professional wrestling, upon whom I stumbled one night while flipping through the myriad channels of our cable TV. The visual impact is the same: beefy. And then there's the price: also beefy.

Lindell Audio, a Swedish professional-audio company, was founded in 2010 by recording engineer Tobias Lindell, and claims to offer equipment "by engineers, for engineers." Tobias Lindell specifies the features and functions that he wants each product to incorporate; the actual circuit designs are by others. Although Lindell's corporate headquarters are in Sweden, the products are manufactured in China, and are competitively priced.

Things didn't start off auspiciously. I'd been after Symphonic Line's Klaus Bunge for more than a year to send me the Kraft 400 Reference monoblocks. Finally he called. He said he was going to be in town for a few days, and he had with him a pair of what he described as his "traveling" Kraft 400s, which he proposed to leave with me.