Solid State Power Amp Reviews

Loudspeakers used during the evaluation of these amplifiers were mainly the Wilson WATTs and Puppies and KEF R107s, though Avalon Eclipses, Acoustat Spectra 1100s, MB Quart 490s, and Epos ES11s also made appearances. Front-end components consisted of a Linn Sondek/Lingo/Ekos/Troika setup sitting on an ArchiDee table to play LPs, a Revox PR99 to play 15ips master tapes, and, at various times, a Meridian 208 CD player, the Stax DAC-X1t and VTL Reference D/A processors driven by Meridian 602 and Wadia WT-3200 transports, or the Krell MD-1/SBP-64X combination to play CDs.

Preamplification first consisted of the Expressive Technologies transformer hooked into a Mod Squad Phono Drive EPS and a Threshold FET ten/e line stage, this combination then replaced by the French YBA 2 preamplifier. My Mod Squad Line Drive Deluxe also saw service as the system control center for CD replay. (Recently upgraded to the latest spec, the Mod Squad improves on its predecessor's already stunningly transparent presentation of musical detail.) The D/A processors were connected to the preamplifier with 0.75m lengths of AudioQuest Diamond, while the power amplifiers were connected to the preamplifier via 15' lengths of AudioQuest Lapis unbalanced interconnect. Speaker cable was 2m lengths of AudioQuest's new Dragon.

For comparison purposes, I used the Stereophile-owned sample of the Krell KSA-250 that Robert Harley wrote about last January (Vol.14 No.1, p.170), the magazine-owned pair of Mark Levinson No.20.5 monoblocks that I reviewed in September 1989 (Vol.12 No.9, p.138), and an Audio Research Classic 60, though this has been retubed since I reviewed it in September 1990 (Vol.13 No.9, p.134). Levels during the comparisons were matched to within ±0.1dB at 1kHz using my Mod Squad Line Drive Deluxe to pad down the more sensitive amplifier of each pair. (While this procedure in itself will change that amplifier's sound to some extent, I tried to account for this by comparing the sound with the Line Drive set to no attenuation with the sound of it out of circuit.)

The most important change made to the system was one that held up the writing of this review for several months, such was its anticipated impact. Though my listening room is well-equipped with wall sockets, there are actually only two 15A circuits serving these outlets. Ever since I had converted what had hitherto been our house's master bedroom into my listening room, I had intended to run new circuits to it. Somehow, there always seemed to be more urgent jobs that needed to be done around the house—new roof, new main drainage, new bathroom, new windows, new stucco, etc.—but finally this Spring there was enough electrical work to be done that we managed to attract the interest of a local contractor. ("Choosing a contractor" is a phrase that, in my experience, is more true turned upside-down: they choose you—if you can supply references and show a willingness to both give them money on an unlimited payment schedule and allow them to become part of your extended family. Having sunk what could have been the money for our child's education into the fabric of our home, we find the omnipresent Eldon character in TV's "Murphy Brown" to be only too real.)

But I digress. For less than the cost of a budget power amplifier—a mere $373.45—the electrician ran two new 30A lines to the listening room, one with the hot on one side of neutral, the other on the other. Each had its own circuit breaker and each fed two hospital-grade wall sockets. (These orange receptacles grasp the prongs of AC plugs with a clasp akin to the Vulcan death grip.) All source components and the system preamplifier were plugged into an Inouye AC conditioner, in turn plugged into one of the new lines; power amplifiers were plugged into the other new line.

The sonic effect was nothing short of stunning. Within the context of a power amplifier's characteristic sound quality, bass fundamentals relatively dropped away to minus infinity, such was the increase in their weight, while the WATT/Puppy's "hump" in the upper bass became considerably less bothersome. Yes, the characteristic sounds of components were not changed—black was not rendered white—but the differences between those characters was heightened, the overall quality of each enhanced. The sonic contrast knob was turned up a notch, if you will, the blacks becoming a deeper black, the whites becoming more brilliant.

There is no doubt in my mind that installing these dedicated AC lines was the single most cost-effective improvement I have ever made to the sound of my system. If you can bring new AC power to your listening room without too much disturbance to your house or household—and you can find an electrical contractor who doesn't feel that he would be in danger of diminishing his social status by taking on your work—do it.—John Atkinson