Now it is a reality, the vinyl record is experiencing a second youth. For an apparently growing number of fans, black pastel has become an essential complement to modern streaming and downloading uses. A number of reasons are invoked to explain this revival madness, but one in particular returns very regularly and never fails to cause much heated debate among enthusiasts: the “vinyl sound.” Without intending to end a debate that will undoubtedly be unleashed for many years, this dossier presents some elementary notions that allow a rational understanding of this sentiment.
A little history
First, let’s go back a few decades: The “33 laps” were born on June 18, 1948 during a press conference held by the American record company Columbia Records. At this time, the most common home audio medium is 78 rpm – a 25 or 30 cm diameter disc, covered with a natural polymer in which a spiral groove is recorded representing a monophonic sound wave. This groove is traversed by a reading needle as the disc rotates, as the name suggests, at a speed of 78 revolutions per minute. The 33 rpm record uses this same concept, but it takes advantage of the technological advances of its time to replace the natural polymer with a synthetic polymer, polyvinyl chloride (PVC).
Armed with these arguments, vinyl is about to become a standard for home audio. Widely adopted by the general public since the mid-1950s, it will accompany the considerable advances made in the second half of the 20th century in the fields of sound recording and (re) production: improvement of electronic amplifiers; definition of a standardized equalization that guarantees the transparency of the frequency response in most of the audible spectrum (the famous RIAA curve) in 1954; appearance of the stereo in 1958 … All this will lead to the birth and development in the 1960s of the concept of “high fidelity”, of which vinyl will continue to be the exclusive medium for almost 20 years. It was not until 1982, the release date of a certain compact disc, that vinyl’s hegemony was finally questioned.
On paper, optical media designed by Sony and Philips feature a number of revolutionary improvements. Of course, its small size and immunity to mechanical wear are notable examples, but they are not the only ones: the transition to digital promises incredible sound transparency, happily surpassing that allowed by vinyl. But lovers of beautiful sound do not pretend to be satisfied with simple theoretical data and many of them, not ready to abandon a format they have appreciated for so long, reject this supposed superiority of the CD. Thirty years later, it is still his arguments that lead some purists to believe that vinyl would have this famous “grain” that would allow the medium to maintain its sound quality king throne, compared to digital media.
The arguments
The “heat” of vinyl
33 rpm is often said to be distinguished from CDs and other digital formats by its “warm” sound. To understand this qualifier, we will have to talk about bandwidth problems: the range of reproducible audio frequencies for each medium.
When it comes to vinyl, this bandwidth is absolute … unlimited. Since it is a purely analog device, there is no theoretical limit to how often a disc slot could vibrate the pen. Of course, the practice does not fit this ideal: among other reasons, when the master’s degree is carried out, the strong mechanical stresses suffered by both the recording head and the disc material cause noise, inaccuracies and attenuations at very high frequencies. . However, the fact remains that a very high quality vinyl record can effectively store sound information at frequencies up to around 50 kHz. On a more common quality disc, the frequency range generally reaches around 23 kHz.
Things are different in the case of digital modulation: the famous Nyquist-Shannon theorem tells us that the maximum frequency reproducible by a digital signal is half the sampling frequency of that signal. Specifically, for a CD sampled at 44.1 kHz, the maximum playable frequency is 22.05 kHz. A really lower value than vinyl. Enough to talk about CD inferiority? No, because this value is still much higher than the hearing limit of the human ear (which is generally, optimistically, at 20 kHz for a young ear in full possession of its means).
But then where is the audible difference … if it really exists? This could have been, in the first days of the CD, in the filtering suffered by the signal upstream of its fixation in the support. In fact, the Nyquist criterion tells us that not only sampling at 44.1 kHz cannot allow frequencies to reproduce beyond 22 kHz, but that these frequencies must be completely removed from the sound signal before sampling, to avoid the aliasing phenomenon. A condition that was realized at the time only by low-performance analog filters, offering in particular a very imperfect phase response in the high spectrum. The result was a distortion that could be clearly heard and gave the sound a certain acidity, a metallic character. From there the bad reputation of the CD was born.
The “softness” of vinyl.
Vinyl’s reputation for producing a “softer” sound than digital is explained in part by the decrease in treble, which basically resembles the infidelity of sound in the original mix, but may also be associated with the theme of saturation. A form of distortion that is sought in this case to avoid as much as possible, saturation occurs when the signal to be recorded exceeds the maximum amplitude allowed by the recording medium. It can take different forms, which sound very clearly in the ear: they therefore oppose analog saturation and digital saturation.
In the case of digital recording, the value of this maximum amplitude is perfectly defined: it corresponds to the value of a sample “one by one”. If the input signal exceeds this value, it results in the sudden appearance of a plateau on the recorded waveform; This is called a hard cut.
In the case of a vinyl record, the amplitude not to be exceeded corresponds to that which causes the groove to oscillate by a distance equal to the pitch of the turns. Exceeding this limit can cause the slot to become tangled, and therefore the disc cannot be read. When recording the master, the signal is passed through a limiter responsible for restricting the slot to its authorized width. This limiter, if it works purely analogically, does not produce a clipping as strict as digital saturation; By gradually reducing the effect of an increase in the input signal until the limit is reached, it causes distortion that is much less unpleasant to hear than the strong clipping effect.
The “dynamic” of vinyl
The argument that is regularly heard today as justification for a supposed superiority of vinyl on CD, is the only one on our list that does not find its origins in the early years of digital support. It must be said that, at this precise point, neither theory nor practice seems to leave the slightest possibility that the analog disk will contest the victory of its adversary: while the 16-bit quantization of the CD gives it a dynamics of 96 dB , the noise The background inherent in vinyl allows it to reach, at best, only about 70 dB; in the usual cases, we prefer to have 60, even 50 dB.
But then what are we talking about when we extol the superior dynamics of vinyl? We are really talking about a very real phenomenon, a consequence of the evil of the century of sound, the ignominious War of the Loudness. While all digital media still regularly suffer the ill effects of this relentless rush for volume, vinyl appears to be relatively safe. With its reputation for precisely being appreciated by audiophiles, it sometimes benefits from mastering at a lower level, guaranteeing you a significantly higher dynamic range.
