![]() At the end of the article Hiraga discusses amplifier #11 (Fig. B), shows an almost total absence of harmonic components beyond the third. Any change in the relative amplitude of these components would alter the “color” of the violin. Reference is made to a violin, which produces a sound that also shows many (up to 20) harmonic components. Hiraga argues that higher distortion levels are not in themselves objectionable if the harmonic components show an orderly, monotonous decrease. In particular, amplifiers where the harmonic distortion spectrum does not monotonically decrease, or where specific harmonics are absent, may sound less agreeable even if the absolute distortion levels are very low. According to his experience, there is a correspondence between a gradual decrease of higher harmonic components and the subjective quality of an amplifier. Hiraga discusses the distortion spectra of various amplifiers. In his article (“Amplifier Musicality,” aX March 2004, p. It is with hesitation and timidity that I should cross (s)words with such an eminent audio personality as Jean Hiraga, but this hesitation and timidity is overridden by my search for technical correctness and understanding. However, the particular pattern of harmonic distortion in an amplifier is extremely significant and can provide important indications of its subjective qualities it is not necessarily wrong to refer to “musicality of distortion.” This spectrum analysis technique can also be applied to audio amplifiers, but as yet few people have been interested enough to analyze the actual content of the measured distortion (whether 0.5% or 0.0005%). The slightest modification of the relative levels of these harmonics will change the spectrum of the signal fed to the loudspeakers and hence the tonal “color” of the violin, making a Stradivarius sound like a very cheap violin, for example. ![]() It is important to note that the tonal color or “personality” of the violin lies in the high-order harmonics from the 4th to the 20th, whose levels are extremely low compared with the second or the third. ![]() This is not simply a question of taking certain measurements or conducting blind listening tests on amplifiers, but an attempt to show that a particular measurement may result in an indication of the ability of an amplifier to reproduce a musical sound.įigure 1 and Table 1 (See Figura A1,2,3) show the spectral composition of a violin note with its various harmonics and their relative levels. However, some particular measurements have been made which may help to reconcile the engineers and the listeners. This article does not intend to discuss in detail the relationship between a particular electronic circuit design and its subjective result, as this is far too large an undertaking. This causes endless debates between the “golden eared” listener and the engineer one quoting the position of the distortion meter needle the other talking about the special tone of piano x of year y. Despite this state of affairs it is interesting that valve amplifiers, which often have a distortion level at least 100 times greater (e.g., 0.5%) may sound subjectively no more, and can sound a lot less, distorted than transistor designs in spite of the higher measured level. Modern amplifier designs are nowadays capable of very low measured harmonic distortion, on the order of 0.005% or even 0.0005% levels which can only be measured with elaborate test instruments. We start by transcribing the first part of Jean Hiraga’s article. The original article appeared in audioXpress March 2004 and the resulting conversation was published in audioXpress October 2005. The debate was caused by an article titled “Amplifier Musicality - A Study of Amplifier Harmonic Distortion Spectrum Analysis” by Jean Hiraga, which originated comments by Jan Didden, Dennis Colin and a subsequent response by Jean Hiraga. Three audio experts discuss the role of distortion levels in what we hear.
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