Audio Research D-150T
His huge stereo amplifier was, in its time, a breakthrough in tubed design, both in power output, and, in the more elusive aspects of reproducing a facsimile of a concert hall sound. Even the best solid-state designs could not then reproduce the three dimensions, the depth, of a real-world soundfield, much less its width, and reproduce these with something like the full range of dynamic contrasts. This amplifier could. Not only that, but throughout most of its range, the 150 captured the fundamentals and harmonics of the music, particularly the frequencies from the midrange on up. Thus, it had a hard-to-define (then) quality of naturalness, call it rightness, that made it unique. For experienced listeners, the 150 was such an overpowering (literally as well) experience by contrast, that its audible flaws were overlooked (highly colored bass, overly romantic midrange colorations, and a drooping top octave). Did I forget to mention the heat it generated and the number of tubes that failed? Yes, I did, but it had its teeth into the essential truth of music and it wouldn’t let go. In that regard, it was a singularity.
Mark Levinson ML-2
The ultimate in snob appeal for its sky-high cost (in the day), the quality of both parts and build, the momentous and cutting heat sinks, all designed to offset its Class A power output of less than 35 watts. Those watts were clean, clean, clean and analytic in a way other solid-states weren’t. At its best and in the areas in which it excelled, it gave new weight to the word “transparency.” (The ML-2 was created before Mark Levinson and its designer, Tom Colangelo, were absorbed into the innards of the Harman-Kardon octopus.)The ML-2 worked best as a mid-range amp, and its virtues show to fullest extent on an electrostatic (it was designed, it is said, for the Quads). I heard it at its best as the central speaker in Levinson’s massive HQD speaker system (H: Hartley, the woofer; Q: the midrange Quad electrostatic; and D: Decca ribbon tweeter), awesome in its day and an inspiration for the creation of the QRS-1D.
Electro Research A-75
This unit was designed by John Iverson, one of the high-end’s most memorable characters, around whom many a story, even legend hath sprung up. The solid-state A-75 was built for the military, perhaps for a radar installation. It was thus built to military specs (and overbuilt for audio listening purposes). So, it was said only a few units were left over for Iverson to sell to the general public. When they worked without breaking down, they were unlike, in sound, anything else on the market. The thing I remember best about them was their incredible purity, both at the tightly defined and taut bass frequencies on up into the, like their designer, ethereal ionospheric regions. Iverson was also legendary for developing a “force-field” speaker that, it is said, the military had its evil eye upon for some dark purposes. (Legend: It could make solid-objects disappear into a nowhere dimension.) There were other designs that did not quite materialize either, including a strain-gauge cartridge/preamp. No one, to my knowledge, ever heard one of those gizmodos. Later on, Iverson simply disappeared, after one or more runs in with the law, or, perhaps, to his alternate business base in Singapore. Many have tried to find him but no one has, so complete is the mystery. (Legend: He was assassinated. Maybe not. Maybe he simply fed himself into his force-field speaker.)
Conrad-Johnson Premier One
This was the first high-powered tube amplifier designed by Lewis Johnson and it had a quality I had not encountered in a tubed unit before: authority. It spoke with a kind of dynamic truth that was undeniable. I’ve been re-reading the review I wrote, wondering whence that authority. Perhaps the quality of “authority” here that was distinctive and that so impressed me lay in the basics. That is, Johnson had got the midbass right, which, to this point, no tubed amplifier had done. The critical range of the midbass (say 40 to 80 Hertz) is where the fundamentals of music lie, and this is exactly the region in which other tubed designs sounded either bloated and bloomy, or anemic and antiseptic. The Premier One, however, got these basic frequencies right and more importantly, their resulting harmonics. And, simultaneously it also got the dynamics right—yes, the other units could play midbass notes at the loud end of the ffff spectrum, but not fully at both ends, including the softest. Dynamics contrasts, those going from microsoft (not MSNBC) to very loud, are the defining characteristic of the real thing. So when you heard the Premier One play music, you believed it. Conrad-johnson has never produced an amplifier, even its solid-state ones, that sounds less than believable. Thus its gear you can almost buy blind-folded, knowing you’ll get something true.