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The Aleph Null, or 0, represents Nelson Pass's maiden product under the Pass Laboratories banner. When he left Threshold several years ago, Pass had the luxury of starting over with a clean slate, and decided immediately that he wanted to design a single-ended MOSFET amp. The result is aptly named after Georg Cantor's first transfinite number: Aleph Null, the gateway to higher-order infinities. Just as Cantor's transfinite mathematics stretched minds with its novel conceptual view of the infinite, the Pass Aleph 0 tantalizes the imagination with a new dimension in the future of solid-state…
The Aleph is extremely well-built, and, unlike a tube amp, requires no periodic maintenance—it's apparently geared for a long life. As Pass explains in the owner's manual: "In 15 years, the electrolytic power-supply capacitors will get old. Depending on usage, you will begin to have semiconductor and other failures between 10 and 50 years after date of manufacture. Later, the sun will cool to a white dwarf, and after that, the universe will experience heat death."
Sound
During its lengthy stay in my listening room, the Aleph drove both Sound-Lab A-1 and Audiostatic ES-100/SW-100…
Steven Stone compared the Aleph 0 and the Aleph 1.2 in November 1997 (Vol.20 No.11):
My first compare-and-contrast exercise pitted the Pass Aleph 1.2 against the smaller, $8000/pair Aleph 0. While the amps shared certain family traits, they did not sound identical. The 1.2 had a certain ease, regardless of the music's demands, that eluded the 0. Paradoxically, the Aleph 0s did have a slightly more specific soundstage focus, but that precision broke down when they were dynamically stressed. Also, the Aleph 0 seemed to be faster-sounding on dynamic transients. The horns on Paquito D'…
Sidebar 1: Specifications
Description: Single-ended class-A monoblock power amplifier, augmented by class-A push-pull stage. Power output: 75W into 8 ohms (18.75dBW), 150W into 4 ohms (18.75dBW), 250W into 2 ohms (18dBW), 400W into 1 ohm (17dBW). Frequency response: 0dB at DC, –3dB at 100kHz. Input impedance: 8.2k ohms (balanced), 6.5k ohms (unbalanced). Output impedance: 0.01 ohm. THD: <0.2% at 75W (8 ohms), 20Hz–20kHz; <0.1% at 400W (1 ohm), 1kHz. Power consumption: 300W at 75W output.
Dimensions: 12" W × 12" D × 10½" H. Shipping weight: 71lb.
Serial numbers of units…
Sidebar 2: Measurements
A full set of measurements of the Pass Aleph 0 was made in the unbalanced mode—the mode used by DO for most of his listening. Selected measurements were also made in the balanced mode. Unless otherwise noted, the measurements shown are for the unbalanced configuration.
Following the 1/3-power, one-hour preconditioning test, the Aleph 0's heatsinks were hot, though not too hot to touch comfortably. The Aleph 0 is non-inverting in its unbalanced mode; in the balanced, pin 2 is configured as the positive leg, pin 3 the negative.
The Aleph 0's input…
Testing the RF transmission of Kimber Kable, up to 3GHz, at Ben Duncan Research Labs, in 2008. The resulting proof of RF rejection was published on-line by Russ Andrews Accessories in England. (Photo: Naomi Swain).
Editor's Preface: In an article in the October 1995 issue of Stereophile, Professor Malcolm Omar Hawksford used Maxwell's Equations to develop a mathematical model describing the behavior of cables at audio frequencies. Among the predictions of this model were that for good conductors there exists an optimum size of wire for audio signal transmission, and that for a wire larger…
Test Group 1
The first series of tests (figs.4–11) used the 1kHz toneburst signal. In each graph, one of the two traces can be seen to be almost flat. This is always the more tightly controlled response, measured at the amplifier output terminals. Deviations here indicate deficiencies with the amplifier's negative feedback control. The other wilder, more wavy response is the imperfect damping measured at the speaker end. The different responses directly show each of the cables' ability to aid the action of the amplifier's NFB. The ranking (based on the distance between the first negative…
The first series of tests (figs.4–11) used the 1kHz toneburst signal. In each graph, one of the two traces can be seen to be almost flat. This is always the more tightly controlled response, measured at the amplifier output terminals. Deviations here indicate deficiencies with the amplifier's negative feedback control. The other wilder, more wavy response is the imperfect damping measured at the speaker end. The different responses directly show each of the cables' ability to aid the action of the amplifier's NFB. The ranking (based on the distance between the first negative…
Sidebar 1: Test Group
The variety of cables tested alongside the Supra Ply (D) includes examples of generic types that are universally used or accessible (A, B, C) or easily made up (E, F). Other purpose-made audio-grade cables (G–H) were needed to contrast against. They had to be practical and immediately wireable—many audiophile cables are not. In alphabetical order:
A) Zipcord is 0.5mm2 Cross-Sectional Area (CSA) (footnote 1), comprising 16 0.2mm (16/0.2) strands of plain copper in an oval sheath. It's commonly used for table lamps as well as connecting budget speakers.
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Sidebar 2: Further reading
Roger Skoff with Jonathan Scull, "Wires, Insulators, Conductors, & Audio Signals," Stereophile, Vol.18 No.9, September 1995.
Martin Colloms, "Cables, Cables & More Cables, Hi-Fi News & Record Review, June 1985; "Cable Considerations," Hi-Fi News & Record Review, December 1985; "Cable Talk," Hi-Fi News & Record Review, June 1987.
Malcolm Omar Hawksford, "The Essex Echo," Hi-Fi News & Record Review, August 1985, August & October 1986, and February 1987; "The Essex Echo," Stereophile, Vol.18 No.10, October 1995.
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Sidebar 3: The Jenving Approach
Tommy Jenving has been making special audio cables in Sweden since 1976, beginning with a chunky speaker cable, the Supra 2.5. The idea of Supra Ply came more recently, and laterally, through developing and patenting a shielded mains cable called Supra Safe. The idea was to protect studio equipment and humans alike from 50Hz and 60Hz AC fields. Research into reducing power-line radiation indicated that low inductance was the key, and that high cable capacitance was unimportant. Realizing that the pulsating, high–peak-current-flow conditions in speaker…