Description: Vacuum tube mono power amplifier. Rated power output: 150W (8 and 4 ohms, 21.76dBW and 18.76dBW). Frequency response: 20Hz–20kHz, +0, –0.5dB. Input sensitivity: 2V balanced, 2V unbalanced for rated output. Input impedance: 220k ohms.
Weight: 27.3kg.
Price: $4400/pair (1986); no longer available (2018).
Manufacturer: Nestorovic Labs, Kirkland, WA 98034 (1986); company no longer in existence (2018).
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Sidebar: Specifications
Saturday, November 17, all day, Alma Music and Audio (7847 Convoy Court, #101, San Diego, CA 92111) is holding an open house to introduce what they call Dan D'Agostino's masterpiece, the Relentless Monoblock, to the Southern California public. The Relentless power amplifiers will be used to power YG Acoustics' Sonja XV loudspeakers, which are also making their debut in Southern California. The Sonja XV is an extreme, four-tower version of the Sonja. It incorporates everything YG knows about speaker design and was created to celebrate YG's 15th anniversary.
The complete system will consist…
On the morning of November 9th, 2018, Stereophile's caffeinated crew of Jim Austin, Sasha Matson, Herb Reichert, and myself arrived at the New York Audio Show with the intention to invade each exhibitor's room as an opinion-bearing, glad-handing tribe. ("Hello—we've come from Stereophile to put fear into your heart and a quick step to your cueing finger. Now play me some Nils Lofgren!")
That lasted all of two minutes after we entered the first room. The bigger problem, if it indeed it can be called a problem, was the abundance of sonic riches available in many of the rooms. We practically…
Late on Friday at the New York Audio Show, I found myself explaining to an audiophile friend, also in attendance, my reaction to the big room sponsored by ESD Acoustic, and to their huge, extravagant, ostentatious five-way horn system—the one my colleagues Sasha Matson and Ken Micallef described in detail, and about which my colleague Herb Reichert contrasted his favorable experience here in New York with his unfavorable experience at the 2018 Munich show. As configured, the system as displayed would cost some $800,000 here in the United States. I smugly explained to my friend that, in taking…
The super cool Rudy Dupuy of Dupuy Acoustique (in Congers, NY) says he used to make loudspeakers, but then he realized that the time-delayed and out-of-phase reflections from the wall behind the speakers always sabotaged any hope of loudspeaker coherence. So he stopped making speakers and developed the tunable Phase Restoration Acoustical Panel (PRAP). As Rudy tells it, "The PRAP can render a higher level of musical realism than any standard rig—no matter the cost." As the Dupuy brochure tells is, "The PRAP addresses a structural deficiency inherent in the listening room acoustics that…
Some audio products deliver truly superb sound of a kind that really makes all the frustrations of building a high-end system worthwhile; they also require exceptional attention and care. The Counterpoint SA-4 is a case in point. With the right speakers, it competes for the title of "Most Transparent Amplifier Available at Any Price." On the other hand, this amplifier steadily loses output power as speaker impedance drops; it must be carefully matched to the right speaker. Then, and only then, can it produce one of the finest musical experiences available.
Technical Description
The SA…
Sidebar: Specifications
Description: Output-transformerless (OTL) tubed monoblock power amplifier. Feedback: overall, voltage loop; local, degenerative cathode. Power output: 190W into 16 ohms (25.8dBW), 140W into 8 ohms (21.5dBW), 80W into 4 ohms (16dBW). Frequency range: 0.8Hz–100kHz. S/N ratio: 92dB. Harmonic and IM distortion, 100 watts out into 8 ohms: typically 0.220.75%. Input impedance: 100k ohms. Signal polarity: non-inverting. Power consumption: 200 watts, idle; 700 watts, maximum.
Dimensions: 19" W by 6.75" H by 19" D. Weight: 120 lb/pair.
Price: $5225/pair (1986); no…
A few issues back, in my review of the Mark Levinson No.26 and No.20 (May 1988, Vol.11 No.5), I mused on the fact that the preamplifier, being the heart of a system, had a more significant effect on sound quality in the long term than, say, the loudspeakers. It was worth spending more on a preamplifier, therefore, than on loudspeakers. Needless to say, this viewpoint was regarded by many readers as dangerously heretical. I decided, therefore, to investigate the sonic possibilities of budget-priced preamps in this issue, even the most expensive being less than one-tenth the price of the Mark…
Sidebar 1: Review System
Putting my customary preamplifier, the Krell KRS-2, to one side, the references used for this review were the $635 Audio by Van Alstine Super PAS (reviewed in October 1998), and the $659 PS Audio 4.6 (reviewed in September 1988 by Tom Norton) used with its normal external power supply, not the $469 M-500 upgrade. For reference purpose, the RIAA response of the PS 4.6 is Flat through almost the entire audio band, with a well-extended bass response, though it starts to roll off at the top of the top audio octave.
Power amplification was provided either by…
Sidebar 2: Measurements
Fig.1 shows the frequency response of the complete preamplifier, measured via the phono inputs with the tone controls out of circuit. This is commendably flat between 40Hz and 30kHz, with any error within the tolerance of the inverse network. There is a faint hint of lift between 3kHz and 16kHz, however, which may tie in with the subjective nature of the treble. Integral infrasonic filtering curtails the response below 25Hz, this sensible in view of the less-than-ideal turntables likely to be used with this inexpensive component. The measured response rolls off…