I was talking last winter to Musical Fidelity's Antony Michaelson, who had been enthusing about his forthcoming stereo amplifier, the AMS100. It would be physically enormous—almost a yard deep—and commensurately heavy at 220 lbs. Despite its bulk, its maximum rated output would be just 100Wpc into 8 ohms. It would also be expensive, at $19,999. And to cock a snoot at environmentalists and their concerns, the AMS100's output stage would be biased into class-A up to its rated 8 ohm power, meaning that, even when not playing music, it will draw…
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The AMS100
The AMS100 is basically a scaled-up version of Musical Fidelity's 50Wpc AMS50, a sweet-sounding amplifier that I used to drive Sonus Faber speakers at a "Loudness Wars" demonstration I did at Denver store Listen-Up in May 2010. Like the AMS50, the AMS100 is a bridged design with both hot and cold speaker terminals for each channel each driven by a complete mono amplifier. But whereas the AMS50 has a single power transformer and a single bank of eight pairs of electrolytic capacitors to supply the positive and negative voltage rails for both the hot and cold amplifiers, the…
The AMS100 is basically a scaled-up version of Musical Fidelity's 50Wpc AMS50, a sweet-sounding amplifier that I used to drive Sonus Faber speakers at a "Loudness Wars" demonstration I did at Denver store Listen-Up in May 2010. Like the AMS50, the AMS100 is a bridged design with both hot and cold speaker terminals for each channel each driven by a complete mono amplifier. But whereas the AMS50 has a single power transformer and a single bank of eight pairs of electrolytic capacitors to supply the positive and negative voltage rails for both the hot and cold amplifiers, the…
Sidebar 1: Specifications
Description: Solid-state, bridged, two-channel power amplifier with class-A output stage and switchable balanced and unbalanced inputs. Rated output: 100Wpc into 8 ohms (20dBW), 200W into 4 ohms (20dBW). Peak output voltage: 80V p–p. Peak output current: 200A p–p. Frequency response: 10Hz–40kHz, +0/–0.4dB. Input sensitivity: 650mV for 100W into 8 ohms. Input impedance: 50k ohms, balanced and unbalanced. Damping factor: 200, equivalent to an output impedance of 0.04 ohm. THD+noise: <0.005% unweighted. Signal/noise: >110dB, A-weighted, ref. maximum power.…
Sidebar 2: Associated Equipment
Digital Sources: Ayre Acoustics C-5xeMP & DX-5 universal players; Apple G4 Mac mini running OS10.5.8, iTunes 10, Pure Music 1.80; Shuttle PC with Lynx AES16 and dual-core AMD Athlon processor running Windows 7, Foobar 2000, Adobe Audition 3.0; dCS Debussy, Benchmark DAC1, Logitech Transporter D/A converters; Halide S/PDIF Bridge, Musical Fidelity V-Link USB-S/PDIF converters.
Preamplifiers: Simaudio Moon Evolution P-8, Ayre Acoustics K-5xeMP.
Power Amplifiers: Classé CT-M600, MBL Reference 9007 monoblocks.
Loudspeakers: Audience Clairaudient…
Sidebar 3: Measurements
To take these measurements, I used Stereophile's loan sample of the top-of-the-line Audio Precision SYS2722 system (see the January 2008 "As We See It" and www.ap.com). Before doing the testing, I ran the Musical Fidelity AMS100 at one-third its rated power for 60 minutes, which thermally is the worst case for an amplifier with a class-A/B output stage. However, an amplifier with a class-A output stage runs cooler when under load. At the end of that period, the chassis was warm, with a temperature of 104°F (40°C), though the heatsinks were hotter, at 116°F (46.6°C…
Today's New York Times carries a brief obituary notice of the passing of audio innovator, Peter Pritchard, on August 23 in Austin, Texas at the age of 83. Peter founded Audio Dynamics Corporation in New Milford, CT in the early 1960's. His original ADC-1 ("Tip mass: 0.6 mg. Compliance. 20x10–6cm/dyne, all directions. Playing weight: 1 gram or less in top quality arms") was a breakthrough product. Indeed, all ADC pickups were notable for their extremely high compliance and low tracking forces and he pursued this approach through a series of successful designs including the well-known ADC-10,…
The video for Colin Stetson’s “The Stars in His Head” (Dark Lights Remix), directed by Isaac Gale and Dan Huiting. Kinda lovely, kinda creepy, kinda perfect for this chilly, gray day.
Colin Stetson's powerful record, New History Warfare, Vol.2: Judges, available from Constellation Records, was reviewed in the July 2011 issue of Stereophile.
Zola Jesus - Seekir by sacredbones
Here’s a new track from Zola Jesus’ upcoming record, Conatus, to be released by Sacred Bones Records on October 4. The track is called “Seekir” and suggests a more polished sound for Miss Nika Rosa Danilova. Combining elements of goth, industrial, pop, opera, and noise, Danilova seems to still be searching for her voice, which is exactly as it should be for a 22-year old with an extremely promising future.
Let her keep searching. I'll follow wherever she goes.
KEF and I go way back. As a very young man in the 1960s, I was obsessed with building speakers, and that was just about the time that KEF founder Raymond Cooke was revolutionizing driver design by using new synthetic materials for cones and surrounds, and experimenting with such innovations as transmission-line–loaded midrange drivers. I found it all very heady and, by direct import from the UK, obtained versions of the oval, flat-diaphragm B139 woofer, the Bextrene-coned B110 and B200 woofers, and the T-15 and T-22 dome tweeters. Fifty years ago, this was all cutting-edge speaker technology…
I usually begin with vocal recordings because a) a good loudspeaker will permit the listener to make a human connection with a realistically reproduced human voice, and b) voices make me focus on the midrange, the part of the audioband that conveys most of the musical information provided by instruments and voices alike. In this regard the Q900 was remarkably good, reproducing a wide range of male and female voices with presence, and with no spatial distinction between fundamentals and sibilants. Solo voices, including that of Sara K. on her Don't I Know You from Somewhere? Solo Live (CD,…