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The existing N.O.S. inventory is undoubtedly polluted by such rogue tubes. And with the high prices commanded by the likes of M-O Gold Lions, the temptation to falsify a tube's true origins becomes great. The problem, however, extends to new production as well. Bad batches of new tubes are just as likely to be sold as is the plant's premium production. Prospective buyers may get hurt, not only because they got ripped-off in the first place, but also from subsequent physical damage to the amp—a tube arc could easily take out a whole circuit board, causing extensive damage.
Sidebar 1: A Bit of History
In the July 1936 RCA Review, R.S. Burnap recounted the development of the 6L6 at RCA's Radiotron Division. The power triode operating in class-A was recognized as the ideal output configuration—at least where its low efficiency (about 25%) and moderate power output were not practical obstacles. The power pentode, already around for several years at this time, was capable of class-A operation with nearly twice the plate efficiency of a triode, while requiring less than a third of the drive signal. The pentode's inherent fly in the ointment was rather large…
Sidebar 2: Specifications
Description: All-tube amplifier with class-AB, push-pull output stage. Output transformer tap: 5 ohms (factory-set). Output power (at 1.5% THD): 145Wpc into 8 ohms (21.6dBW), 180Wpc into 5 ohms (20.5dBW), 169Wpc into 4 ohms (19.3dBW). Frequency response: 10Hz–40kHz ±0.5dB. Input sensitivity: 1.4V for full output. Input impedance: 100k ohms. S/N ratio: 80dB ref. 180W into 5 ohms. Power consumption: 240W quiescent, 480W full-power.
Dimensions: 19" W by 7" H by 13" D. Weight: 48 lbs.
Serial numbers of units tested: MANEM175007/08.
Price: $4800/pair (1995…
Sidebar 3: Measurements
Following its 1/3-power, one-hour preconditioning test, the Manley 175 was no warmer than normal for a tube amplifier. Its input impedance at 1kHz measured 146k ohms; its output impedance was 1.6–1.7 ohms at low and middle frequencies, decreasing slightly to just under 1.5 ohms at 20kHz into 4 ohms. These are middle-of-the-road values for a tube amplifier, in my experience. The Manley's performance—particularly its overall in-system frequency response—will be somewhat dependent on the partnering loudspeaker.
The 175's voltage gain into 8 ohms measured 28.…
Some time ago I wrote about the need for high-end audio companies to constantly reinvent themselves: You may be receiving accolades for your latest and greatest product, but you'd also better be well along the path to developing its replacement. High-end audio is a field of constant change; no product remains supreme for long.
Stereophile strives to also meet this ideal. A few years ago a well-known hi-fi manufacturer told me, "Don't change a thing." Fortunately, I ignored his advice, but even if I hadn't, Stereophile would have changed. A year later, our lineup of writers had changed…
A letter in the April 1988 issue (Vol.11 No.4) from reader Harold Goldman, MD, decried the seemingly appalling failure rate of high-end products, citing a $10,000/pair power amplifier, an $11,000 turntable, and a $1500 CD player which had all been reported in recent issues as having failed during or shortly after testing by Stereophile. And Dr. Goldman's list was far from complete. We have also experienced during the past couple of years the failure, or inoperation upon delivery, of two $2500 solid-state power amplifiers, a $1700 subwoofer, a $5000 hybrid amplifier, two pairs of $1200…
KEITH JARRETT: Paris Concert
Keith Jarrett, piano
ECM 1401 (839 173-2, CD only). Peter Laenger, Andreas Newbronner, engs.; Manfred Eicher, prod. DDD. TT: 50:17
Keith Jarrett, piano
ECM 1401 (839 173-2, CD only). Peter Laenger, Andreas Newbronner, engs.; Manfred Eicher, prod. DDD. TT: 50:17
Keith Jarrett's recent emphasis on recording and performing the music of Bach (footnote 1) has left its inevitable traces on his solo improvisations. Never a contrapuntal slouch, Jarrett reaches new heights of grace, allusion, and determined develoment in his new Paris Concert, particularly in the first ten minutes.
This is Jarrett's most satisfying solo outing since 1982's Concerts (footnote 2). The 38 minutes of…
In the four years since our last readership survey, Stereophile's circulation has grown by one third, from 45,000 to over 60,000 (footnote 1). We thought it time, therefore, to commission new numbers, from specialists Mediamark Research Inc. (footnote 2). Table 1 shows the demographic breakdown of the magazine's readers. While the launch of CD did bring more women into the audiophile fold almost 10 years ago, the proportion of Stereophile's female readers has not changed since 1988, at just over 1% (footnote 3). At one of the panel sessions at the 1992 High End Hi-Fi Show in Los Angeles, a…
Before launching into Stereophile's first-ever report on a Mark Levinson product, an important point needs to be clarified. Although Mark Levinson products were originally made by Mark Levinson, they are no longer. Au contraire, Mark Levinson products are now being made by Madrigal, Ltd., which bought Mark Levinson Audio Systems' assets and trademark two years ago. Mark Levinson's products, as distinguished from Mark Levinson products, are now being manufactured by a company called Cello. But the subject of this report, the Mark Levinson ML-7A preamplifier, is a product of Madrigal, Ltd.,…
Also unusual are the M-L's balance adjustments. These are separate switches, each of which adjusts its channel in 1dB steps up to +5 and down to –4. Below the –4 dB point, each control completely shuts that channel off. Again, this is of value for trouble-shooting, but I don't understand the need for separate balance controls. Intrachannel tracking is not a problem with a balance control, and ganging a pair of the pots that MLAS now uses separately could not possibly impair the sound. Perhaps Madrigal can explain to us the reasoning behind this design decision.
Sonics
I had a brief…