The Bose 901 has created more of a stir in audio circles than any other loudspeaker we can think of, with the possible exception of the original Acoustic Research system. Much of the 901's popularity is attributable to Julian Hirsch's rave report in Stereo Review, and there is no doubt but that Amar Bose's compellingly convincing ads had their effect, too. But these things alone could hardly account for the 901's popularity.
Not only does the venerable vacuum tube refuse to lie down and die, as everyone predicted when audio went solid-state; it continues to deliver better performance than anyone had imagined it could. Only a few years ago, we could characterize "the tube sound" as being sweet but soft at the high end, rich but loose in the midbass, deficient in deep bass, and bright and forward, usually with excellent reproduction of depth. Since then, we've seen the introduction of what might almost be called a new generation of tube amplifiers, which rival solid-state units in those areas where tubes used to have weaknesses, but have given up little of the tube's sonic strengths.
Warning to Purists: Despite certain qualities about the ESL-63 speakers which you will probably like, Quad equipment is not designed primarily for audiophiles, but for serious-music (call that "classical") listeners who play records more for musical enjoyment than for the sound. Quad's loudspeakers do not reproduce very deep bass and will not play at aurally traumatizing volume levels, and Quad's preamplifier is compromised through the addition of tone controls and filters, all for the purpose of making old, mediocre, and/or worn recordings sound as listenable as possible.
The Sound-Lab electrostatic loudspeakers are legendary. Many serious audiophiles have heard of them, and rumors of their existence abound in audio circles. But, like gnomes, UFOs, and poltergeists, Sound-Lab loudspeakers are sufficiently hard to find that it is sometimes difficult to prove to skeptics that they exist at all. Well, I can now report that they do. As proof of this contention, I can point to the two which are actually occupying solid, tangible space in my listening room at this very moment. I have even taken a photo of them, which will be published along with this report if they leave any sort of an image on the film emulsion. (Many such apparitions do not!)
For those of us who have succumbed to the enticements of surround-sound for music, Audio Research's SDP1 is both vindication and cause for rejoicing: vindication because surround-sound's acceptance by such an ultraconservative, uncompromising company as ARC will give it a respectability in the high-end community that it never enjoyed before, and cause for rejoicing because someone has finally done music surround right.
The D-250 is the flagship of Audio Research's power amplifier range and, at 250 watts per channel, is the most powerful all-tube stereo amplifier currently available in the US. Under the circumstances, then, it is not surprising that it should also be one of the heaviest and largest.
This is something we don't see too often: an entirely new approach to power amplifier design. As Quad points out in its literature for the 405, class-A operation of transistors provides the lowest distortion, but drastically limits the amount of power an output transistor can deliver without overheating. (Most transistor amps use class-AB output operation, in which each of a pair of power transistors handles part of each signal cycle and shuts down during the other part. Imperfect synchronism between the two halves causes the familiar "crossover distortion," which accounts for most solid-state sound. In class-A operation, each output transistor draws current though the entirety of each signal cycle, eliminating the crossover transition but doubling the amount of time current is drawn, and thus tending to cause the transistor to heat up more.)
Few people in the audio business would deny that John Curl is an audio design genius—arguably the greatest one of our generation. He designed and built the electronics for Mobile Fidelity's SuperMaster and David Wilson's (of Wilson Audio) UltraMaster tape recorders, two of the three best analog recorders in the world. (The other is Keith Johnson's home-brew unit.) He designed the JC-1 head amp and JC-2 preamplifier sold under the Mark Levinson name some years ago. He designed head amps for SOTA, Michaelson & Austin (TVA), and has done consulting work for more high-end companies than you can shake a stick at.
Several issues back, we reviewed rather enthusiastically a pre-production prototype of this preamp. The original was an unprepossessing-looking device on two chassis, interconnected by a 3' umbilical, with a squat little preamp box and an even squatter power supply with humongous cans sticking out the top. We averred that it sounded nice. The production model is so nicely styled and functionally smooth that we wondered if it might not be another Japanese product. 'T'ain't.