Sidebar 3: Measurements
The Moon Equinox inverted absolute polarity, something that needs to be allowed for in comparisons with other players. Its maximum output level at 1kHz was both to specification and conformed with the "Red Book" Standard at 2.01V RMS, while its output impedance was a usefully low 99 ohms. Error correction was superb, the player coping with gaps in the data spiral up to 1mm without any audible glitches. Only on track 32 on the Pierre Verany test CD, which has 1.5mm gaps, did it stumble.
The Equinox's frequency response was flat within the audioband, with a…
A committed audio equipment reviewer operates at the front line of audio subjectivity. Working on behalf of a readership made up of consumers thirsting for independent, informed opinion and advice, a reviewer is commissioned by the editor of a magazine to produce reports with a technical and subjective content on a wide range of available audio products. These reviews must be both fair and completed at short notice on a relatively small budget. How is it possible to do this successfully, when a similar task undertaken by an industrial laboratory or test house would take five times as…
Errors in frequency response of only marginally greater amplitude may impart subjective alterations in timbre or tonal balance. The sense of "immediacy"—the sensation of proximity to the performers—may also be affected. Perspective—the feeling of front-to-back distance in the soundstage—is a related parameter. Other effects include the feeling of transparency in the reproduced sound. Loudspeaker designers become keenly aware of these subjective effects, which may be deliberately or otherwise hidden within the normal tolerances of the amplitude/frequency responses of a nominally well-designed…
If it is accepted that such effects exist, it is our duty as engineers and scientists to understand and control them to our advantage. The High End
If any sense is to be made of it, then true high-quality audio, the "High End," must be set apart from the audio business as a whole. Quality audio is a relatively small, specialist industry composed mainly of companies run by enthusiasts who in the main believe in what they're doing, namely the advancement of the fidelity of reproduced sound. Yet this industry is founded on a solid scientific base, melding mechanics, acoustics, and…
Such attitudes tend to suppress freedom of thought and innovation. Furthermore, science is littered with discoveries which were largely accidental; had they been ignored simply because they did not conform to the status quo, the loss to mankind would have been incalculable. Examples include the chance arrival of the airborne penicillium mold in a particular scientist's laboratory, while centuries earlier, Kepler had been attempting to solve the problem of planetary motion within the conventional paradigm. Ptolemaic and Copernican laws only allowed for purely circular orbits. Kepler's…
It took a full three years of commercial development before CD sound broke through the "10" level, which in 1990 represented the average for the whole industry. Players scoring 5 on the current 24-maximum scale are usually found in cheap music centers, while a player that wins respect in the more critical areas of the industry will score 14 or more. Genuine audiophile players are rare and score above 16, generally costing in excess of $1000. Recent high-end players and processors using both Bitstream and multi-bit DAC technology have shown that a score of 24 is attainable; no doubt this…
Another revealing example is the effect of printed circuit boards on amplifier sound quality. In one example, an amplifier was prototyped in hardwired form using phenolic paper pin board, with a physical layout and connection wiring precisely conforming to a correctly designed printed circuit board. Thoroughly measured and auditioned, it gave an excellent performance. Second prototypes were then built using pre-production pcbs. By intensive measurement, the two were judged to be almost identical, yet the sound quality of the second version was significantly poorer. After some…
• Metallurgy: Many establishment audio engineers consider that Ohm's Law is wholly sufficient to describe current flow in a wire, and that all metallic conductors must sound the same owing to the fundamental property of free electron mobility in this class of material. However, there is now strong evidence to indicate that the choice of element or alloy for a conductor, its metallurgical history, and its absolute purity all affect the sound quality. This finding, unwelcome for those working in this field, cannot be ignored. It seems a cruel twist of fate that of the many conducting materials…
Sidebar: Massed violins & digital sound
Why should the sound of massed violins should be so susceptible to processing damage? Given that all links in the chain are non-linear to some degree, either in terms of transfer function or in terms of delayed energy storage, the potential for audible damage to a given musical signal is proportional to its complexity. The intermodulation products for just a few tones look horrifying on a spectrum analyzer display. Imagine a musician sounding two notes on his violin: high-order harmonics are predominant, with perhaps 15 significant components.…
VPI Industries' TNT turntable and JMW Memorial tonearm have evolved through several iterations over the last two decades. Some changes have been large, such as the deletion of the three-pulley subchassis and the introduction of the SDS motor controller. Others have been invisible—a change in bearing or spindle material, for example, or the way the bearing attaches to the plinth. And, as longtime Stereophile readers know, I've been upgrading and evolving along with VPI, most recently reporting on the TNT V-HR turntable (Stereophile, December 2001).
But about the time I was…
