EP1269486B1 - Symmetrical or pseudosymmetrical audio low-level signal cable - Google Patents

Abstract

The invention relates to a symmetrical or pseudosymmetrical audio low-level signal cable with at least one signal lead (6, 7), at least one earth wire (5), and a screen (4). If more than one signal lead (6, 7) is provided, the distance between those leads is eight times the size of their respective diameters, however at least 4 millimeters. The signal leads (6, 7) have a respective distance to the earth wire (5) of at least two millimeters and the screen (4) has a respective distance to the signal leads (6, 7) of at least one millimeter. The screen (4) can be electroconductively connected to the earth wire at least on one end. The respective signal lead (6, 7) or earth wire (5) consists of maximally two solid metal wires. The audio low-level signal cable allows for a more precise spatial and tonal reproduction and a more realistic localizability of sound sources in complex sound-producing bodies.

Description

The invention relates to a symmetrical or pseudo-symmetrical small audio audio cable, with at least one signal conductor, at least one ground conductor and with a shield for the at least one signal conductor.

Symmetrical audio small signal cables are used mainly in the professional and semi-professional sound technology for the transmission of low-voltage analog audio signals. By low voltage levels are meant those of at most 30 volts, in particular 10 volts, normally 4 volts. Symmetrical cables offer the advantage over asymmetrical or pseudo-symmetrical cables that interfering signals are eliminated or at least greatly reduced by interference cancellation. Symmetrical audio small signal cables are usually made of two centrally arranged conductors, which the + signal and transmit the signal, as well as constructed from a shield enclosing the two signal conductors, which is usually connected to the ground at both ends of the cable. The shield is used in addition to the transfer of phantom power, especially when connecting to condenser microphones. To keep the cable as flexible and easy as possible, the distance between the signal conductors to each other and the diameter of the shield is kept small.

Electrically amplified musical instruments, where the sound signal is generated by pickups, usually do not have symmetrical connections. The asymmetric cables used here consist of a centrally arranged signal conductor, which is coaxially enclosed by a shield. The shield is connected to ground at both ends. Again, the diameter of the shield is kept small for reasons of handling the cable.

Pseudo-balanced cables are asymmetrical cables consisting of two centrally arranged conductors and a shield coaxially enclosing the two conductors. The one central conductor is the signal conductor, the other the ground conductor. The shield is electrically connected at one end of the cable to the ground conductor.

The symmetrical, asymmetrical and pseudo-symmetrical small audio signal cables described above usually use strands as signal conductors. Strands consist of a bundle of very thin metal wires, which are usually twisted together.

The invention is based on the object, a symmetrical or pseudo-symmetrical audio small signal cable in such a way that with him with simple production, the changes that the transmitted Sound signals experienced by the cable are reduced compared to the known cables.

The object is achieved according to the invention that in the presence of more than one signal conductor, the distance between them is at least eight times larger than their respective diameter, said center distance is at least four millimeters, that or the signal conductor to the ground conductor depending on a center distance of have at least two millimeters, that the shield to the or the signal conductors has a respective distance of at least one millimeter, and that the shield is electrically conductively connected at least at one end to the ground conductor.

In a very advantageous embodiment, the cables according to the invention use solid metal wires instead of strands made up of many thin wires.

According to the distances mentioned, it is possible and in many cases even advantageous that the ground conductor is located outside the shield.

In another embodiment, the shield according to the invention is connected via a switch to the ground, so that they can be completely separated from the ground in the event that no interference signals are interspersed.

In another embodiment, the shield is connected to the ground via an ohmic resistor. Conveniently, a resistance of one kilohm to fifty kilohms is used.

The two embodiments described above can also be combined, i. that, for example, in a connection of the shield to the ground via a resistor, a switch is additionally provided, by means of which the shield can be separated from the ground.

Symmetrical cables according to the invention are capable of transmitting analog sound signals, for example from microphones, in such a way that the spatial and tonal imaging of the instruments takes place more precisely, particularly in the case of complex sound bodies. Playback appears more realistic in terms of locability of sound sources and timbres.

In the context of the invention, for example, pseudo-symmetrical cables make it possible for electric guitars to have a more present sound, but without being sharp or shrill. Dynamic range of the tool seems bigger.

Cables according to the invention can be used wherever tone signals of a low voltage level are transmitted in analog form. In particular, they are suitable for transmitting the sound signals from microphones and the signals from pickups of electrically amplified musical instruments.

Fig. 1

einen schematischen Querschnitt eines erfindungsgemässen Audio-Kleinsignalkabels.

Fig. 2

einen schematischen Querschnitt eines weiteren erfindungsgemässen Audio-Kleinsignalkabels in vergrösserter Darstellung.

In the following the invention with reference to an embodiment of a symmetrical Tonsignalkabels is explained in more detail with reference to the drawings. It shows:

Fig. 1

a schematic cross section of an inventive audio small signal cable.

Fig. 2

a schematic cross-section of another inventive audio small signal cable in an enlarged view.

Fig.1 shows a symmetrically formed audio small signal cable 10, which is used in particular in professional and semi-professional sound engineering. This cable 10 has a first electrical signal conductor 6 and a second electrical signal conductor 7, which are each separated by an insulation 6 ', 7'.

According to the invention, the axial distance A1 between these signal conductors 6, 7 is at least eight times greater than their respective diameter. At a minimum, however, this center distance A1 should be four millimeters. In addition, the signal conductors 6, 7 to ground conductor 5 each have a center distance A2, which is greater than two millimeters, and also the distance a of the signal conductor is also 6.7 to the shield 4 each greater than one millimeter. The shield 4 is electrically conductively connected at one end to the ground conductor 5.

In the present embodiment, a commercial two-pin, DNM Single Solid Core cable 1 of the company Virtual Reality Audio Systems, Brentwood Essex, GB with a first signal conductor 6 and a second signal conductor 7 is provided for the cable 10, wherein between these signal conductors 6, 7 a Center distance A1 of 5.6 mm, a respective conductor diameter of 0.4 mm and a cable length of 5 m is provided. This single solid core cable 1 is attached with adhesive tape to a polyamide film 2 of 0.5 mm thickness and 12 mm width and guided centrally through a commercially available corrugated pipe 3 made of hard PVC with an inner diameter of 14 mm and an outer diameter of 18.5 mm. The corrugated tube 3 is coated with a commercially available, aluminum-coated shrink tubing 4 with the name 'Shrink-Shield' by Thomas & Betts, Egelsbach, D. Outside the corrugated tube 3, a commercially available copper strand 5 is freely laid with a conductor diameter of 0.5 mm.

The one signal conductor 6 of the central single solid core cable 1 is now at both ends of the cable with the plus signal, the other signal conductor 7 of the central single solid core cable is connected on both sides with the minus signal. The copper strand 5 is connected on both sides with the ground or the phantom power. The aluminum-coated shrink tubing 4 is electrically conductively connected on the side of the signal sink with the ground or the phantom power, advantageously by means of a switchable contact.

In the context of the invention, the signal conductors each consist of a solid metal wire with a diameter of 0.2 to 1.2 mm, in particular 0.30 to 0.65 mm.

Fig.2 shows an audio signal cable 20, in which the two signal conductors 26, 27 and the ground conductor 25 are arranged to extend in a plane. The ground conductor 25 is in the middle in the symmetrically constructed cable 20, during which the signal conductors 26, 27 are placed at the same distance to this. The two signal conductors 26, 27 are also enveloped by a respective sheath 22 and a respective shield 24, which may be formed, for example, as a wound aluminum foil or the like. The ground conductor 25, which is likewise enclosed by a casing 22 ', is, however, arranged outside the two cross-sectionally oval shields 24. These conductors 25, 26, 27 are embedded in a total of a plastic outer shell 23.

The signal conductors 26, 27 are made of solid copper wire, preferably silver-plated outside and arranged within the scope of the invention to each other at an axial distance A1 of, for example, approximately 13 times the copper wire. The center distance A1 is, for example 6.5 mm and the diameter of the wire 0.51 mm. In which Ground conductor 25, the same copper wire can be used with a diameter of 0.51 mm, which results in each a center distance A2 to the signal conductors of 3.25 mm. The latter as well as the ground conductor are for example embedded in a foamed plastic layer 22, 22 '.

beträgt, wobei der in Millimetern anzugebende Durchmesser D des Signal- oder Masseleiters, je nach dem welcher dicker ist, genommen werden soll. Die resultierende Zahl gibt dann den Achsabstand A2 in Millimetern an, wobei der bereits oben erläuterte Achsabstand A2 von mindestens zwei Millimetern einzuhalten ist.In the context of the invention, the signal conductor or conductors should have a center distance A to the ground conductor, which at least $$\mathrm{A}\mathrm{2}\mathrm{=}\mathrm{6}\mathrm{\times }{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^{\mathrm{2}}\mathrm{+}\mathrm{D}$$

is, wherein the to be specified in millimeters diameter D of the signal or ground conductor, whichever is thicker, to be taken. The resulting number then indicates the axial distance A2 in millimeters, whereby the axial distance A2 of at least two millimeters already explained above must be observed.

In a pseudo-symmetrical audio small signal cable according to the invention, which is not shown in detail, a signal conductor and a ground conductor are provided. These conductors are enclosed by a corresponding shield. The shield is connected via an ohmic resistor on one side to the ground conductor, the ohmic resistance is 100 ohms to 1 megohm, in particular 1 kilohms to 50 kilohms.

As shielding also come the known variants of braids of conductive materials, metal / plastic film composites, conductive plastic layers and combinations thereof in question.

The one or more signal conductors 26, 27 are each covered with a sheath 22, which consist of a compact or foamed plastic, which expediently has a dielectric constant of at most 3.0. For this sheath, a polytetrafluoroethylene, tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, Polyethylene, polypropylene, a copolymer of α-olefins and ethylene or a mixture of these plastics may be provided.

In another embodiment, the shield is electrically conductively connected to the ground at one end and a capacitor is connected at the other end between the shield and the ground. Conveniently, a capacitor with a capacitance of 10 picofarads to 100 nanofarads is used. In this way, high-frequency noise, such as may be caused by radio stations, be eliminated.

The invention is sufficiently demonstrated with the embodiments explained above. Of course, the structure of such a cable according to the invention could look different.

If the signal conductors 6, 7 should be provided with different diameters, then the minimum center distance should start from the smaller diameter of the signal conductors 6, 7.

Claims (14)

1. Symmetrical or pseudo-symmetrical small audio signal cable with at least one signal conductor (6, 7), at least one mass conductor (5) as well as with a shield (4) for the at least one signal conductor (6, 7), characterised in that the axis distance (A1) between the signal conductors (6, 7), when more than one of the same is present, is at least eight times greater than their relevant diameter, whereby this axis distance (A1) is however at least four millimetres, in that the signal conductor(s) (6, 7) are each positioned at an axis distance (A2) of at least two millimetres from the mass conductor (5), in that the shield (4) against the signal conductor(s) (6, 7) is positioned at a distance (a) of at least one millimetre, and in that the shield (4) can be connected in an electrically conductive way with the mass conductor (5) at least at one of its ends.
2. Symmetrical or pseudo-symmetrical small audio signal cable according to Claim 1, characterised in that the relevant signal (6, 7) or mass conductor (5) consists of a maximum of two solid metal wires.
3. Symmetrical or pseudo-symmetrical small audio signal cable according to Claim 1 or 2, characterised in that the signal (6, 7) and mass conductor(s) (5) each consist of a solid metal wire with a diameter of 0.2 to 1.2 mm, in particular of 0.30 to 0.65 mm.
4. Symmetrical or pseudo-symmetrical small audio signal cable according to one of the preceding Claims 1 to 3, characterised in that the mass conductor (5) is located outside of the shield (4).
5. Symmetrical or pseudo-symmetrical small audio signal cable according to one of the preceding Claims 1 to 4, characterised in that at least one casing enclosing the signal conductor(s) (6, 7) is envisaged, the same consisting of a compact or foamed plastic comprising a dielectric constant of at most 3.0.
6. Symmetrical or pseudo-symmetrical small audio signal cable according to Claim 6, characterised in that the casing consists of polytetrafluoroethylene, tetrafluoroethylene/ethylene copolymer, tetrafluoroethylene/hexafluoropropylene copolymer, polyethylene, polypropylene, a copolymer of α-olefins and ethylene, or of a mixture of these plastics.
7. Symmetrical or pseudo-symmetrical small audio signal cable according to one of the Claims 1 to 6, characterised in that the shield is connected with the mass conductor on one side via an ohmic resistance, whereby the ohmic resistance is 100 ohm to 1 megaohm, in particular 1 kiloohm to 50 kiloohm.
8. Pseudo-symmetrical small audio signal cable according to one of the preceding Claims 1 to 6, characterised in that the shield is connected with the mass conductor via a condenser at one end.
9. Symmetrical or pseudo-symmetrical small audio signal cable according to Claim 8, characterised in that the shield is connected with the mass in an electrically conductive way on one side and in that a condenser is switched between the shield and the mass on the other side, whereby the capacity of the condenser is 10 picofarad to 100 nanofarad.
10. Symmetrical or pseudo-symmetrical small audio signal cable according to one of the Claims 1 to 8, characterised in that the shield (4) is connected with the mass conductor (5) via a switchable contact and/or via an ohmic resistance.
11. Symmetrical small audio signal cable according to one of the preceding Claims 1 to 10, characterised in that a first signal conductor (6), a second signal conductor (7), a shield (4) enclosing the same and a mass conductor (5) are envisaged.
12. Pseudo-symmetrical small audio signal cable according to one of the preceding Claims 1 to 8, characterised in that a signal conductor, a shield enclosing the same and a mass conductor are envisaged.
13. Pseudo-symmetrical small audio signal cable according to one of the preceding Claims 1 to 8, characterised in that the signal conductor(s) (26, 27) is/are positioned at an axis distance (A2) of at least A2 = 6 x D² + D from the mass conductor (25), whereby the diameter (D) of the possibly thicker conductor is stated in millimetres and the resulting figure lists the axis distance (A2) in millimetres, whereby this axis distance should be at least two millimetres.
14. Use of a symmetrical or pseudo-symmetrical small audio signal cable according to one of the preceding Claims for connecting microphones, of musical instruments connected with sound recorders, as well as for the general transmission of analogue sound signals with frequency levels of no more than 30 volt, preferably no more than 10 volt.

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