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.)—John Atkinson