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.
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…
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.
Sound
During its lengthy stay in my listening room, the Aleph drove both Sound-Lab A-1 and Audiostatic ES-100/SW-100…
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'…
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…
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…
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…