- 26 May 2008
- 834
Να ζητήσω συγνώμη για την παρεμβολή. Θα σωπάσω αμέσως μετά.
Επίσης ας μην βάλει τις φωνές κάποιος, θα γίνει προσπάθεια να υπάρξει και μια σύντομη μεταφραση.
Καλό θα ήταν να σχολιάσετε επ αυτού. Πρέπει να κλείνουν κάποια θέματα σιγά σιγά, υπάρχουν και πολλά άλλα προβλήματα και θέματα για συζήτηση.
http://www.audiodesignline.com/showArticle.jhtml?articleID=192200304
Measurement System for the Characterization of Hi-Fi Audio Cables
By Giovanni Bucci et al
TechOnline
(07/21/2005 0:00 À¼ EDT)
The transmission of an electrical analogical signal between two devices requires a suitable cable that should allow for transferring it with low distortion and losses. Ideally a cable does not introduce power-losses and the electrical signal applied at the input is transferred integrally to the output, without any modification of its parameters. Unfortunately, in real conditions, there is always an alteration of the transmitted signal, because of reactive and resistive (parasite) parameters of the interconnection system constituted by the cable and the two end connectors.
The behavior of a real interconnection system can be evaluated considering different parameters, such as the signal attenuation and distortion that can become critical with the increasing of the frequency. The analysis of the problem can be carried out taking into consideration a set of electrical parameters, depending on the adopted modeling methodology. The traditional approach refers to the lumped elements: resistance (R), inductance (L) and capacity (C), as shown in the electrical model of Figure 1. The behavior of a cable can be also described by means of the transfer function. Moreover, it is also important to analyze the electric and magnetic coupling between different lines of the interconnect system, because they can be a source of crosstalk noise.
Of the different application fields that can be mentioned as a basic reference for the problem under consideration, one may refer to the audio signal transmission in high-fidelity (Hi-Fi) applications.
Figure 1: Lumped parameters model of a Hi-Fi cable.
Hi-Fi audio signal bandwidth spans the entire audible range of frequencies, from the 41 Hz (and below) of bass guitar and synthesizer to the 20 kHz harmonics of keyboards and cymbals. Professional applications demand a wide bandwidth interconnecting system to preserve the signal integrity. In this field, there are two main kinds of applications:
In recent years, the production of these devices has grown out, even if some manufacturers publicize special cable qualities without any established scientific basis.
Even if, from a technical point of view, it is normal that the properties of a connection system may affect the transmitted signal, the perceived subjective differences between cables can have different explanations.
Most would agree that the ideal connecting system is one which brings us as close to the experience of the original musical event, hearing the music as it was recorded without adding or missing signal components (cable neutrality). This ideality can be obtained only with zero series inductance and zero parallel capacitance, providing an unlimited transmittable bandwidth.
Some cable manufacturers adopt a different philosophy, based on the use of networks, filters and additional elements to improve the audio signal by altering it, producing colorations that destroy the natural, musical reproduction. The result is artificial and contrived, rather than ideal and neutral, even if it can be appreciated by some people more than a neutral system.
According to the IEC standards, the measurement of cable parameters requires the adoption of complex procedures, also because some standards refer to cable for general purposes. The aim of this paper is the development of a measurement procedure for the performance evaluation of the high-quality cables adopted for professional audio applications. The main features of these high-performance cables are: attenuation lower than 0.25 dB in the frequency range of DC-50 kHz, resistance around to 0.1 ohm, and inductance in the range of 6-24 H.
In the paper we will report and discuss the experimental results related to the characterization of a set of Proel Die-hard professional cables.
Επίσης ας μην βάλει τις φωνές κάποιος, θα γίνει προσπάθεια να υπάρξει και μια σύντομη μεταφραση.
Καλό θα ήταν να σχολιάσετε επ αυτού. Πρέπει να κλείνουν κάποια θέματα σιγά σιγά, υπάρχουν και πολλά άλλα προβλήματα και θέματα για συζήτηση.
http://www.audiodesignline.com/showArticle.jhtml?articleID=192200304
Measurement System for the Characterization of Hi-Fi Audio Cables
By Giovanni Bucci et al
(07/21/2005 0:00 À¼ EDT)
The transmission of an electrical analogical signal between two devices requires a suitable cable that should allow for transferring it with low distortion and losses. Ideally a cable does not introduce power-losses and the electrical signal applied at the input is transferred integrally to the output, without any modification of its parameters. Unfortunately, in real conditions, there is always an alteration of the transmitted signal, because of reactive and resistive (parasite) parameters of the interconnection system constituted by the cable and the two end connectors.
The behavior of a real interconnection system can be evaluated considering different parameters, such as the signal attenuation and distortion that can become critical with the increasing of the frequency. The analysis of the problem can be carried out taking into consideration a set of electrical parameters, depending on the adopted modeling methodology. The traditional approach refers to the lumped elements: resistance (R), inductance (L) and capacity (C), as shown in the electrical model of Figure 1. The behavior of a cable can be also described by means of the transfer function. Moreover, it is also important to analyze the electric and magnetic coupling between different lines of the interconnect system, because they can be a source of crosstalk noise.
Of the different application fields that can be mentioned as a basic reference for the problem under consideration, one may refer to the audio signal transmission in high-fidelity (Hi-Fi) applications.
Figure 1: Lumped parameters model of a Hi-Fi cable.
Hi-Fi audio signal bandwidth spans the entire audible range of frequencies, from the 41 Hz (and below) of bass guitar and synthesizer to the 20 kHz harmonics of keyboards and cymbals. Professional applications demand a wide bandwidth interconnecting system to preserve the signal integrity. In this field, there are two main kinds of applications:
- The interconnection between audio systems in which the output system has an high impedance Z[SIZE=-2]L[/SIZE] (about 100 kΩ and the input system a low impedance Z[SIZE=-2]S[/SIZE] (in the range of 80-800 Ω); in these conditions the transmitted signal has low power (approximately some tens of milliwatt);
- The interconnection between amplifiers and acoustic diffusers in which the transmitted analogical signal transfers power to the diffusers, which have typical impedance values in the range of 4-16 Ω.
In recent years, the production of these devices has grown out, even if some manufacturers publicize special cable qualities without any established scientific basis.
Even if, from a technical point of view, it is normal that the properties of a connection system may affect the transmitted signal, the perceived subjective differences between cables can have different explanations.
Most would agree that the ideal connecting system is one which brings us as close to the experience of the original musical event, hearing the music as it was recorded without adding or missing signal components (cable neutrality). This ideality can be obtained only with zero series inductance and zero parallel capacitance, providing an unlimited transmittable bandwidth.
Some cable manufacturers adopt a different philosophy, based on the use of networks, filters and additional elements to improve the audio signal by altering it, producing colorations that destroy the natural, musical reproduction. The result is artificial and contrived, rather than ideal and neutral, even if it can be appreciated by some people more than a neutral system.
According to the IEC standards, the measurement of cable parameters requires the adoption of complex procedures, also because some standards refer to cable for general purposes. The aim of this paper is the development of a measurement procedure for the performance evaluation of the high-quality cables adopted for professional audio applications. The main features of these high-performance cables are: attenuation lower than 0.25 dB in the frequency range of DC-50 kHz, resistance around to 0.1 ohm, and inductance in the range of 6-24 H.
In the paper we will report and discuss the experimental results related to the characterization of a set of Proel Die-hard professional cables.