FR2606204A1 - Audio-frequency transformer having large dynamic range, with neutralising winding - Google Patents

Abstract

The invention relates to a transformer for small signals in the low-frequency range comprising three windings. The first winding 1 coiled with adjoining turns as close as possible to the magnetic core 4, forming a screen and connected galvanically to earth via one end, and coupled magnetically to a second winding 2 serving as primary consisting of the same number of turns as the winding 1 and which are coupled magnetically to a third winding 3 serving as secondary. The invention can be used as interface system for modern high-definition sources having large dynamic range such as compact discs and moving-coil cells. The matching of these sources to the preamplifier enables their auditory characteristics to be considerably improved.

Description

HIGH DYNAMIC AUDIO-FREQUENCY TRANSFORMER WITH WINDING
OF EUTRALIZATION
The present invention relates to devices for transmitting signals and more particularly to casting devices in the audio-frequency domain up to 30 kHz. The primary and secondary windings are often interleaved so as to reduce the dispersion of the fluxes which manifests between them. The proximity of these windings relative to the magnetic core increases the inter-winding parasitic capacity and the mass.

 In order to reduce the capacitive effects, electrostatic screens were used between the coils and the magnetic core of the low frequency transformers. This technique is inconceivable in audio transformers intended for modern sources of high dynamic modulation that are Cotnpact-Lisc and phono-reader cells with moving coils because of the mechanical characteristics and the too high capacity between the coils and the mass, that it introduces.

 The present invention presents an audiofrequency transformer, comprising an anti-interference neutralization winding which eliminates the capacitive coupling distributed between the windings and the magnetic core.

 In an embodiment allowing the best performance of the invention, the neutralization winding is made up of a number of turns similar to that of the primary winding and of the same section wound in the same direction. One end of the neutralization winding is connected to ground while the other end remains free. This allows a simple construction while obtaining a constant electric field with respect to the mass while avoiding the electrical losses.

 Figure 1 shows a section of the transformer according to the plar. axial.

 2 shows a sectional view of the turns in position on the core.

 Figure 3 shows the electrical diagram and arrangement of the transformer co'Dinase6.

 Figure 4 shows 2 transformers enclosed in a box.

If one refers more particularly to FIG. 1 one can see there the section of the differential transformer according to a preferred embodiment of the present invention. According to this arrangement, the copper neutralization winding 1 is wound as close as possible to the carcass 4 made of 90% ferro-nickel sheets. The section of the copper wire is 2/100 of a millimeter in the present case for the use of small signals lower than the milli
Watt. After having previously isolated the carcass 4 with a plant insulator 5, the primary winding 2 adapted to the input impedance will be wound there. The best performance has been obtained when the neutralization windings 1 and primary 2 have the same number of turns. The primary 2 and secondary 3 circuits are themselves separated by a plant insulator 5, according to the rules of the prior art of manufacturing. transformers.

The secondary hoeing 3 will be adapted in impedance to the receiving circuit.

 The arrangement of the neutralization windings 1, primary 2 and secondary 3 on the magnetic core 4 and represented in FIG. 2. It will then be noted that the turns are contiguous and with superimposed layers.

Figure 3 shows the electrical diagram of the invention
According to the principles of the invention, a neutralization coil 1 is provided between the magnetic carcass 4 and the primary coil 2. This neutralization coil 1 considerably limits the parasitic capacitance between the primary circuit 7 and the ground.

 According to the principles of the invention, the neu tra'ismtion winding 1 created in fact a dynamic shielding sui prevents any appreciable coupling by an electric field between the pr1r1re winding 2 and the ground. This neutralization winding 1 is wound in the same direction as the primary winding 2 and constitutes an open circuit, that is to say that at least one of its ends is not connected to any other element of the transformer. . In the present preferred embodiment, since this end is not connected, there will be no flow of current through the winding. Therefore the neutralization winding 1 has no appreciable effect on the magnetic field of the transformer, and consumes no substantial amount of energy. Furthermore and still according to the principles of the invention, the other end of the neutralization winding 1 is connected to the end grounded of the primary 2 which is adjacent to it.

 As a result, the potential state of the neutralization winding 1 is turns for turns of equal amplitude and of equal sign to that of the primary winding 2.

As an indication, and not limiting, such a system is used as line interface for Compact-Disc and / or cells with moving coils, as shown in figure 4. In the metal case are mounted 2 transformers T1 and T2 in the case of '' stereophonic use, wired to two groups of standard sockets (RCA) 2 for inputs El and E2, 2 for outputs
S1 and S2. The wiring is carried out in shielded wires F and soldered between the transformers T1, T2 and the sockets El, E2, S1 and S2.

 The invention can be used as an interface system for modern sources of high dynamic range and high definition signals such as Compact Discs and voice coil cells. The adaptation of these ati-preamplifier sources makes it possible to considerably improve their subjective aspect, when listening.

Claims (3)

REVE.vICATIONS 1. Audio-frequency transformer characterized in that it comprises three windings, the first winding 1 wound with contiguous turns as close as possible to the magnetic core 4 forming a screen and galvanically connected to ground, at one end, magnetically coupled to a second winding 2 serving as primary consisting of the same number of turns as winding 1 and magnetically coupled to a third winding 3 serving as secondary. 2. Transformer according to claim 1 characterized in that the winding 1 called neutralization is wound with the same number of turns as the primary 2 whose turns are in the same direction and with contiguous turns. 3. Application of the transformer in stereophony according to claims 1 and 2 characterized in that it comprises a metal case with four connection sockets.