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The SM-SX100 didn't need to be turned up to sound "alive." Yet when I did crank it, it never hardened or glazed over. Still, I found myself using my SPL meter—I frequently turned the volume up way too high because the amp sounded so good, and behaved so well when asked to deliver high SPLs. At high levels, the top end did get to be a bit much, but that will happen with any amplifier. What didn't happen with the Sharp was dynamic compression, image smearing, or flattening—though, of course, the Amati Homage's sensitivity is about 93dB. The SM-SX100's volume control goes to 128. I never took…
Sidebar 1: Specifications
Description: Stereo integrated amplifier with digital (PCM and DSD) and analog inputs, delta-sigma A/D conversion of analog sources, and PWM (class-D) output stage. Preamplifier section: Sensitivity (analog input): 350mV RMS/50k ohms (1kHz, 100W). Power amplifier section: 64Fs 1-bit switching (Fs=44.1kHz) output stage. A/D noiseshaping: seventh-order delta-sigma modulation. Sampling frequency: 2.8224MHz (64Fs) (Fs=44.1kHz). Master clock frequency: 5.6448MHz (128Fs) (Fs=44.1kHz). Low-pass filter: fourth-order Butterworth type. Output power: 100Wpc into 4 or 8…
Sidebar 2: Associated Equipment
Analog sources: Simon Yorke, Michell GyroDec SE turntables; Rockport Sirius III turntable/tonearm; Graham 2.0, Immedia RPM2 tonearms; Lyra Parnassus D.C.t, Lyra Helikon, Transfiguration Temper Supreme cartridges.
Digital sources: Sharp DX-SX 1 prototype SACD player, Musical Fidelity X-Ray CD player, Marantz DR17 CD recorder.
Phono stage: Audio Research Reference.
Cables: Interconnects: Yamamura Millennium 6000, Electra Glide, Silver Audio, Wireworld Gold Eclipse. Phono: Kimber TAK silver, Hovland DIN/RCA, XLO Signature 3.1. Speaker: Yamamura…
Sidebar 3: Measurements
Although the Sharp SM-SX100 is really a power D/A converter, I first examined its performance as a conventional integrated amplifier. With analog sources and the volume control set to "128," the '100's maximum voltage gain (into 8 ohms) was 36.7dB with the rear-panel switch set to "8 ohms," 34.75dB set to "4 ohms." A volume-control setting of "81" resulted in clipping with a digital 0dBFS input signal, while the unity-gain setting for analog sources was an indicated "33" ("8 ohms") or "34" ("4 ohms"). The amplifier didn't invert signal polarity via the digital or…
Even though the Sharp follows its output stage with passive low-pass filtering, the aggressive noiseshaping used in the Sharp's digital encoder results in this residual HF noise. There will also be a contribution from its switching output stage. The noise made it difficult to measure the SX-100's harmonic distortion. The bottom trace in fig.4, for example, shows the distortion residual on a 1kHz tone (top trace): it is random HF noise. Using an additional 6th-order passive filter (supplied by Sharp) on the amplifier's output, however, gave the trace shown in fig.5. What distortion the…
Because its output stage is switching between the full ±32V voltage rails all the time, even when there isn't an output signal present, the Sharp doesn't clip like a conventional amplifier. Looking at the output waveform on a 'scope while I drove it into overload—don't try this at home, gentle readers—revealed the sinewave to become triangular in shape, with bursts of ultrasonic noise increasingly becoming apparent on the positive and negative peaks.
I investigated the Sharp's peak power delivery with the Miller Audio Research Amplifier Profiler, a "virtual instrument" (realized on a…
Increasing the measurement bandwidth to 200kHz and changing the input data to 16-bit "digital black" gave the traces shown in fig.11. Again, the high noise floor in the audioband and the 500kHz spectral component can be seen, but so can the full extent of the noiseshaping. The noise peaks at -35dB around 120kHz, even after its processing by the amplifier's internal passive filter!
Fig.11 Sharp SM-SX100, 1/3-octave spectrum of digital black, with noise and spuriae, 16-bit data (right channel dashed).
Finally, I assessed the Sharp's rejection of wordclock jitter using the…
Yamaha once made a loudspeaker shaped like an ear. I felt sorry for the guy (especially if he was an audiophile) who had to write the ad copy explaining why a speaker shaped like an ear would sound better than one shaped like a shoebox or a wedge of cheese. An ear-shaped loudspeaker makes about as much sense as an eyeball-shaped television. But what about a loudspeaker that is designed like a musical instrument?
When Sonus Faber's Franco Serblin began creating his Homage series of loudspeakers (footnote 1) to honor the great violin makers of Cremona—Amati, Guarneri, Stradivari—his design…
When you're accustomed to narrow-baffled speakers, being confronted by two wide expanses of wood can be jolting. Because the Stradivaris have more of a "room divider" presence than most moving-coil–based speakers, they affect room acoustics even when silent. I could "hear" them. I wondered how music—especially the imaging and soundstaging—could not be affected. As I sat down to listen for the first time, the visual cues took me back to 1986, to the first time I heard Harry Pearson's Infinity IRS system, which presented another set of wide-baffled (line-source) speakers just a few feet away…
Given the Stradivari's drive-units and the attention paid to its cabinet, you might expect exceptional dynamic abilities. You wouldn't be disappointed. Like all great, large, expensive speakers, the Stradivari delivered the musical goods with a confident grip at both ends of the scale, and without breaking a sweat. Most noticeable were the low-level dynamics, especially in the bass and midbass region, where, at the ends of familiar bass lines, the speaker seemed to reveal a last bit of decay that had been previously obscured. Played at high SPLs or at a whisper, the Stradivari remained open…