(I'm thinking of a mono record here, or a stereo one in which the signal is at equal amplitude and in phase in both channels, so as to produce purely lateral movement of the cutting stylus.) This will prevent any part of the audible spectrum from hogging too much disc space, and ensure that the groove modulations are, so far as possible, large relative to the asperities of the groove surface, thereby maintaining a good ratio of signal to noise. Ideally, we would want them to be constant-amplitude in nature, so that a given signal level at, say, 100Hz occupies no more or less lateral space than the same at 10kHz. Both are normally velocity transducers, the significance of which will shortly become apparent.ДЇirst, let's consider the nature of the modulations (wiggles, if you like) that we wish to impose on a record groove. The requirement for disc equalization exists because of the nature of the cutting head used to gouge the groove into the lacquer master disc, and that of the pickup cartridge used to replay the pressed vinyl record. Everything the audiophile (though not the design engineer) really needs to know about the subject is here. Yet the subject occasionally reemerges, such as in the recent debate about the 'Neumann ultrasonic time constant.' If the history of and theory behind RIAA/IEC (International Electrotechnical Commission) disc equalization are mysteries to youВ—or have faded from memoryВ—then this article will bring you up to speed and up to date. In the interim, vinyl replay has dwindled to a small if still thriving niche of the hi-fi industry, and a new flush of audiophiles exists to whom the subject of disc equalization may be unknown or, at the very least, arcane. Three decades later, as CD gained ascendance, a large proportion of audiophiles still knew what RIAA equalization was, and a good number of them had some idea or better of what the RIAA EQ curve looked like, and why it was applied.Д«ut that was a generation ago. Until the Recording Industry Association of America hit the headlines in recent years with its antipiracy campaign, the initials RIAA meant one thing to seasoned audiophiles: the vinyl-disc equalization characteristic introduced in the 1950s to standardize what had previously been an anarchy of different EQs.

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