WO2006053992A1

WO2006053992A1 - Improving the quality of analog wideband appliances

Info

Publication number: WO2006053992A1
Application number: PCT/FR2005/002879
Authority: WO
Inventors: Dominique Jouniot; Eric Brandizi
Original assignee: Dominique Jouniot; Eric Brandizi
Priority date: 2004-11-18
Filing date: 2005-11-18
Publication date: 2006-05-26
Also published as: FR2878091B1; EP1856799A1; FR2878091A1

Abstract

The invention concerns the improvement of the operational quality of electronic analog wideband appliances by replacing the capacitors used for filtering and decoupling supply voltages as well as for connection between successive functional elements (2) and (3) by clusters of capacitors whereof the values are uniformly distributed from the low values, more efficient at high frequencies, to high values, more efficient at low frequencies. The improvement is brought about, at each frequency, by the joint action of neighbouring capacitors leading, by summation of their individual frequency responses, to a global linear response.

Description

Improved quality of analog broadband devices. Field of the invention

The present invention relates to electronic devices used to process analog signals in a wide frequency band under good conditions of quality and fidelity.

The present invention is applicable in the generality of such devices. However, to take a specific example and without this constituting a restriction of use, the remainder of this text describes its application to audio or video signal processing apparatus, known as HiFi. These devices are used to collect such signals by means of suitable sources, such as microphones, to reproduce them by means of headphones, loudspeakers, or any suitable device, for conditioning them for wired, wireless transmission. or other, or their storage on an analog or digital media. In such devices, the term Hi-Fi means that the reproduction of the signal, which is always their end goal must be as faithful as possible to the original signal collected by the microphones.

The signals processed by these devices are always intended to be appreciated by human auditors. Thus the fidelity of their treatment must be verified by subjecting them to subjective tests of comparison, approval and preferably with human auditors. This fidelity can also be verified by objectively comparing the signal obtained at various stages of its processing with the fact that it is closest to the source that created it or that made it possible to collect it.

Research on signal processing has shown that the comparison of the temporal waveform of the signal is not sufficient. In fact, imperfections that are virtually undetectable at this level can result in disastrous results for subjective tests, while more visible imperfections may have no impact on the latter. If the examination of the waveform is not a good objective criterion, it is very generally accepted that the linearity of the treatment, the good respect of the phase and the amplitude of the spectral components of the signals and the limitation of the noise level provided by the treatment, all in an appropriate frequency band, constitute criteria ensuring a good correlation with subjective tests.

Thus, to take a non-exclusive, pictorial example, we can consider that the processing of a telephone quality signal is satisfactory if, in a frequency band extending from 300 to 3400 Hz, the distortion of linearity does not exceed 1% or 2%, if the spectral amplitudes are respected within 3 or 4 dB and if the noise level remains at least 35 or 40 dB below the signal level, the respect of the phase not being subject to no special conditions. For a device used for the processing of radio frequency broadcasted musical signals, it is more demanding. The frequency band is widened to the range of 50 to 15000 Hz, the spectral amplitudes must be respected to 1 dB, the noise level must be lowered to -65 dB and the phase must be well controlled.

We start talking about Hi-Fi when the frequency band reaches 20 to 20000 HZ and the noise level -95 dB, the other objective criteria lose their importance to the extent that the modern electronic technology makes it possible to respect them in a perfect way in that no improvement is obtained by pushing them further.

However, demanding users are not content with this level of quality and lead manufacturers to make changes to their products that are not justified by current knowledge of the psycho-physiological mechanisms of human sensory organs, or whose effects on the signal are not observable objectively. On this subject, one can consult David E Blackmer's text "The world beyond 2OkHz" (accessible on the website http://www.drtaastering.com) as well as the document of Dr. Paul Mills entitled "Wideband: The Need For Extended" High Frequency Bandwidth, or Why You Need A Supertweeter "and made public on December 14, 1999 by Tannoy.

This is how some devices manage to process the signal in a frequency band extending up to 15OkHz, whereas no auditory perception is considered possible beyond 20000Hz or 30000Hz and that particular choices components give good subjective results without any correlation of objective measurements. Purpose of the invention

The present invention is in the context that has just been mentioned above. The present invention relates to the improvement of the subjective quality obtained from the apparatuses described above by a particular structure of the capacitive elements used in their manufacture. The fundamental use of capacitive systems in the devices we are interested in is the connection between successive subsets. Audio devices are never required, even if they are of very high quality, to ensure the transmission of the DC component (zero frequency) of the signals. It is sometimes necessary to use successive subsets such that the continuous component at the output of the first is incompatible with the DC component at the input of the second. In general, it is preferable to prevent any continuous component from propagating in the apparatus at its entry and exit.

In particular, placed at the output of an amplifier, this capacitor is a protection against short circuits imposing the output stages a very important electric current. In the case of a short circuit occurring at the downstream apparatus, the capacitor limits the time during which the output stages of the amplifier must provide a very large current that may lead to their destruction.

In the event of a failure of the output stages of the amplifier, this time limitation of the excessive current that can be delivered avoids the destruction of the downstream device (for example, a loudspeaker).

To ensure connections under these conditions, it is essential to set up a capacitor in series on the path taken by the signal, for example at the connection point of a microphone or any external source, between the different amplification stages. or internal processing, at the connection point of an external output or a speaker.

The same method is applicable to modulation cables used to provide links between different devices, such as a CD player and an amplifier, for example. It is common, in this case, to use a capacitor in series at the input and / or the output of such an apparatus, to protect it against the spurious signals polluting the protective grounds which are very generally manifested by snoring. In all cases, the choice of this component is not trivial, both in terms of the value of its capacity as from the point of view of the chosen technology.

This capacitor stores a voltage equal to the voltage difference between the two points between which the signal must be routed. The latter is routed through the current calls between the two elements connected in this way. Figure 2 shows the application of our invention in this case.

In the use just described, the capacitive system used is charged at a determined voltage (supply voltage, or voltage difference between elements to be connected). The correct operation of the device proceeds from the fact that this voltage remains fixed regardless of the current flowing through the capacitive system. This capacitive system must, for this, have, in the frequency band of the signal, the lowest impedance and the smallest possible phase difference.

In both cases, the solution imposes a strong capacity. The calculation of the theoretical value of this capacity is easy depending on the surrounding conditions. The behavior of capacitors with high values, generally realized in electrochemical technology, is bad in high frequency. So it is customary to add in parallel one or two capacitors of lower values but made in a non-electrochemical technology, ensuring better treatment of high frequencies.

Detailed description of the invention

The present invention replaces, in the cases presented above, the capacitor or the group of two or three capacitors by a cluster of capacitors (1) of different values (denoted C, - between C ₁ and CN) whose number can reach fifteen or twenty (there is no theoretical limit to the number of capacities), under the conditions set out below:

The cumulative value of the elements of this cluster of capacitors is equal to the theoretical value determined for the use of a perfect capacitor (or to the smallest value determined to the listening and / or the measurements, bringing a correct reproduction of the lowest frequency sought).

Each capacitor, numbered i, is associated with a frequency band, from the large capacitance values associated with the low frequencies, to the low values associated with the high frequencies, according to a formula such that, without this having any character of exclusivity:

C ₁ - = Ky%

The equivalent capacity of the set is the sum of the capacitances of the N capacitors that make up the cluster:

C = C ₁ + C ₂ + ... + C _N

The influence of this component is easily demonstrable in listening. By applying the principle of multiple values of stepped values, this problem is eliminated by the approximation of the perfect capacitor. This method results in a subjective quality of signal at least equal, and more generally higher than that obtained in direct connection. This superiority over a direct connection by a cable can be explained by the fact that the capacitive connection prevents the transmission of parasitic voltages continuously and at very high frequency. These two types of noise can adversely affect the phase of the signals, by intermodulation, and also, especially with regard to the continuous and very low frequencies (for example, less than 2 Hz), to continuously vary the operating point of the signal. apparatus, including thermally and, inter alia, by their effect on the feedback. It is, moreover, remarkable that experimentally, the best subjective results of the modulation cables (connection between a CD player and an amplifier) were obtained with a total decoupling of the continuous by installing groups of capacities on the hot point, and on the ground connecting the RCA sockets in asymmetrical connection or on the two points of a symmetrical connection. Finally, the use of capacitance groups has been successfully tested on the cables connecting the loudspeakers to the amplifier. Here too, it can be assumed that the use of this method makes it possible to avoid a harmful influence on the feedback of the noise amplifier TBF, as well as the influence of high frequency parasites (located above the audio tape).

The improvement in the quality of the signal obtained with this arrangement of capacitors is fully evidenced by the subjective results mentioned above. However, no objective model or objective measure can predict such an improvement. It is obvious that this arrangement is meaningless if the capacitors are perfect. The research of the effect obtained here must be in the imperfections of the capacitors, in their inductive component and in the losses in the dielectric.

The inductive component of the capacitors gives them a resonance frequency for which they exhibit optimal operation with a reactive impedance and a zero phase shift. The use of a cluster of stepped capacitors makes it possible to have an optimal capacitor at any frequency. In this case, it may even be useful to add to each capacitor a series inductance so as to lower its resonance frequency and further improve the efficiency of the assembly in the low frequencies. This paradoxical operation, which consists in reducing the quality of the capacitors, constitutes, in fact, a neutrodynage allowing the improvement of the response of the device.

In the same spirit, one can look for a similar neutrodynage by the use of resistors inserted in series with each capacitor. Acting directly on the time constant of each capacitor, this operation makes it possible to act on the phase shift curve of the assembly. On the other hand, it is the losses in the dielectric which explain the malfunction of electrochemical capacitors at high frequencies. These imperfections of the capacitors are still poorly known: they are modeled only on a global level from the energy point of view, far from the precise phenomena internal to the materials themselves. Observations that can be made highlight cycles of hysteresis. Beyond the simple differences in technology, it is possible to expect that a given capacitor will have too little capacity to process the low frequency signals and a hysteresis cycle will cause high frequency signal processing. , thus requiring the use of tiered capacitors to ensure correct processing at all frequencies. These hysteresis phenomena can be attributed to fluctuating signal phase shifts as a function of various parameters (intensity, slope of the signal, device impedance and their variations, etc.). These phase shifts are canceled almost completely by the use of groups of abilities. It can also be seen that the capacitor clusters lead to even greater subjective quality if the individual capacitors are different from each other, not only in the value of their capacitance, but also in other of their characteristics such as their operating voltage. and their technological nature (electrochemical, polyester, paper, ceramic, or other). These characteristics affect the characteristics of resistance, self, capacitor frequency response, which themselves may affect the subjective quality of the signals, as stated above.

As part of this search for the improvement of the quality of the devices by the use of capacitor clusters, it has been noticed that this quality improves even more if the elements of these clusters of capacitors are embedded in a silicone resin or , more generally a Resilient product to avoid vibrations. This prevents the capacitors from being subjected to mechanical vibrations of any kind from the power transformers, from loudspeakers or external noises. Such vibrations are likely to induce small variations in capacitance and spurious signals superimposed on them. Useful signals. Brief description of the drawings In the accompanying drawings,

- Figure 1 shows a cluster of capacitors. (1) different values (denoted C, between C ₁ and C _N ) between two functional elements (2) and (3) of an electrical or electronic device,

FIG. 2 shows a cluster of capacitors (1) of different values (denoted by C, between Ci and C _N ) between two functional elements (2) and (3) of an electrical or electronic device and of which each capacitor is mounted in series with a resistor (denoted R ₁ to R _N ) (4),

FIG. 3 represents a cluster of capacitors (1) of different values (denoted C, - between Ci and C _N ) between two elements, one of which is a source system which can be - for example - an amplifier (5) and the other a receiver system which can be - for example - a speaker (6).

Claims

1 - Device consisting of capacitors grouped in a parallel cluster (1) placed between two systems and characterized in that the capacitors that compose it have capacity values distributed regularly from the low values ensuring a fast response time to the signals to high frequencies up to high values keeping a significant electrical charge under the effect of low frequency electrical signals.

2 - Capacitive device according to claim 1 and characterized in that the capacitors that compose it have different operating voltages.

3 - Capacitive device according to all or part of the preceding claims and characterized in that the technological nature of the capacitors that compose it is not homogeneous for the entire cluster (1).

4 - Capacitive device according to any or all of the preceding claims and characterized in that it is used in an apparatus for reproducing sound or high quality images and that it processes broadband analog electrical signals, such as audio and / or video signals.

Capacitive device according to any or all of the preceding claims and characterized in that the assembly is embedded in a resilient material protecting it from vibrations.

6. Capacitive device according to any or all of the preceding claims and characterized in that each of the individual capacitors is placed in series with an inductance to improve the behavior of the assembly in the low frequencies.

7- capacitive device according to any or all of the preceding claims and characterized in that each of the individual capacitors is placed in series with a resistor (4) to improve its response time.

8- Capacitive device according to any or all of the preceding claims and characterized in that it is used to ensure the transmission of electrical signals between two functional elements (2) and (3) of an electrical or electronic device. 9- capacitive device according to any or all of the preceding claims and characterized in that it is used to ensure the transmission of electrical signals between an amplifier (5) and a speaker (6) or a set of speakers.

10- capacitive device according to any or all of the preceding claims and characterized in that it is used to ensure the transmission of electrical signals between a microphone or an external signal source and an amplifier or other functional element of an electrical or electronic device .

11- Capacitive device according to any or all of the preceding claims and characterized in that it is placed on each of the two son used to ensure the asymmetrical transmission (hot spot and ground) or symmetrical electrical signals between a microphone or a signal source an amplifier or other functional element of an electrical or electronic apparatus.