The Koss is handsome, well constructed, and apparently quite durable. Noise rejection is extremely high, but the PRO-4 is not quite as comfortable for long periods as the Sharpe HA-10 (because of a…
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Almost a dead-ringer for the early-model Sharpe HA-10, Koss's PRO-4 ($45) is readily distinguishable by a large knurled protuberance sticking out of the lower part of the right-hand phone. This, in case you've wondered, is a mounting for a "boom-type" lip microphone, for use in speech labs and for communication purposes. (Sharpe and Permoflux also provide facilities for attaching a lip-mike.)
Sidebar 1: Headphone Buying Tips
When auditioning headphones, take along a wide variety of program material. Try to include recordings that use different miking techniques (pan-potting, Blumlein, ORTF, etc.) The ear and brain hear headphones differently from speakers, which changes the way you perceive colorations.
What you hear depends not only on the hardware and software, but also on what's going on inside your head. Don't listen unless you're rested and relaxed. Start by auditioning one of the better 'phones (Class A, B, or top of C in Stereophile's "Recommended Components…
Sidebar 2: Specifications
Description: Over-the-ear, closed-back headphones.
Price: Koss PRO-4, $45 (1963); Koss PRO-4A, not noted (1968); Koss PRO-4x, $85 (1982); PRO/4 AAA Plus, $70 (1991); PRO-4AA, $99.99 (2020).
Manufacturer: Koss Corporation, 4129 N. Port Washington Ave., Milwaukee, WI 53212. Tel: (414) 964-5000. Fax: (414) 964-8615. Web: koss.com.
The VPI Magic Brick is an 8lb block of steel laminations, about 5" by 3" by 2", encased in a nicely-finished oak box for aesthetic appeal and for protecting whatever the brick is sitting on from scratches. Placing the Brick over the power transformer of a piece of electronic gear is supposed to improve the sound of your stereo system.
Before I tried it, I was definitely of two minds about the Brick. Because people I respected had told me that it really did work, I was inclined to believe it. But in my heart I did not really believe that an inert metal block could do anything for an…
Sidebar: Specifications
Description: Passive damping block.
Dimensions: 5" × 3" × 2". Weight: 8lb.
Finish: Wood veneer.
Price: $35 (1982); $149.99 (2020).
Manufacturer: VPI Industries, Ozone Park, NY 11417 (1982); VPI Industries, Inc., 77 Cliffwood Avenue, #5D, Cliffwood, NJ 07721. Tel: (732) 583-6895 (2020). Web: www.vpiindustries.com.
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…