JPS6325402B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording circuit for a multichannel tape recorder.

FIG. 1 shows an example of a recording circuit of a conventional multi-channel tape recorder. During recording, each of the recording/reproducing switches _S1 to _S7 is connected to a contact point R as shown by the solid line in the figure. Recording inputs are input from the left microphone 1a and the right microphone 1b, and are amplified via changeover switches S ₁ and S ₂ and amplifiers 2a and 2b, respectively. The amplified recording signals pass through switch S ₃ and S ₄ , respectively.
The current enters recording current equalizers 9a and 9b consisting of parallel circuits of resistors and capacitors. The signals that have passed through the recording current equalizers 9a and 9b pass through a circuit consisting of the secondary coil 10b of the transformer 10 and the capacitor 12a, and a circuit consisting of the secondary coil 7b and the capacitor 12b of the transformer 7, respectively, and then are transferred to the changeover switch _S5 , After passing through _S6 , the data is recorded on tape by each magnetic head 6a, 6b.

Further, a circuit including the transistor 16, the resistor 15, and the primary coil 10a of the transformer 10, and the transistor 8, the resistor 11, and the primary coil 7a of the transformer 7 each constitute an oscillator.
Recording bias currents induced in the secondary sides of the transformers 10 and 7 by these oscillator outputs are supplied to the magnetic heads 6a and 6b from the secondary side coils 10b and 7b, respectively. The output of the oscillator is also applied to a degaussing head 14, by which the magnetic tape is erased.

When reproducing, the recording/reproducing changeover switches _S1 to _S7 are switched to the contact P side. Therefore, the signals reproduced by the magnetic heads 6a and 6b are transmitted to the amplifiers 2a and 2.
After passing through resistors 3a, 3b and output amplifiers 4a, 4b, the reproduction signal on the left side is amplified by speaker 5a, and the reproduction signal on the right side is converted into audio by speaker 5b.

In the circuit shown in FIG. 1, 13 is a power switch, and 17 is a power source.

However, in the above-mentioned conventional recording circuit, oscillators for supplying recording bias current to the magnetic heads 6a and 6b for recording and playback are required for the number of channels, resulting in a large number of parts and high manufacturing costs. There were flaws.

The present invention eliminates the above-mentioned drawbacks of the prior art,
To provide a recording circuit for a multi-channel tape recorder that has a small number of parts and is inexpensive.

In a multi-channel tape recorder, the present invention provides at least one oscillation circuit for supplying a recording bias current to at least two or more recording heads, and an oscillation coil wound around the core of the oscillation coil of the one oscillation circuit. It is equipped with at least two secondary coils for channels and a capacitor connected in parallel with each secondary coil, and in the recording signal frequency band, the secondary impedance of the oscillation coil is adjusted to the composite impedance of the recording head and recording current equalizer. It is distinctive in that it was chosen to be sufficiently small compared to the others.

The present invention will be explained below by way of examples. Second
The figure shows an embodiment of the invention. The difference between this embodiment and the conventional recording circuit shown in FIG. 1 is that there is one set of circuits that generate recording bias current, and the secondary coils of the transformers connected to each magnetic head are the same. The point is that it is wrapped around the core of. That is, one oscillation circuit consisting of the transistor 16, the resistor 15, and the primary coil 10a of the transformer 10 oscillates the recording bias frequency, and the secondary coil 10 wound around the same core oscillates the recording bias frequency.
The recording bias current induced in the magnetic heads 6a and 7b is supplied to the two-channel magnetic heads 6a and 6b. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same components as in FIG. Furthermore, since the circuit operations for recording and playback are the same as those of the conventional circuit, a description thereof will be omitted.

Generally, the signal oscillated by the oscillator needs to be higher than the highest recording frequency. This embodiment is designed to obtain an oscillation frequency of 30 to 100 KHz, and the secondary impedance of the transformer 10 is high near this oscillation frequency, as shown by curve a in Figure 3, and as it moves away from the oscillation frequency. It gets smaller. On the other hand, the impedance of the magnetic heads 6a and 6b with respect to frequency increases linearly from a frequency of 7 to 800 Hz, as shown by straight line b in FIG. Further, the impedance of the recording power source equalizers 9a and 9b with respect to frequency decreases almost linearly when the frequency exceeds 1 KHz, as shown by curve c. The combined impedance of the magnetic head and the recording current equalizer is as shown by the dotted curve d.

If the secondary impedance of the transformer 10 in the recording signal frequency band is selected to be sufficiently small compared to the composite impedance d of the magnetic head and recording current equalizer, as shown by curve a in Figure 3, multiple channels can be connected to the same core. Even if you wind the secondary coil,
It becomes possible to ignore the electromotive force induced in the secondary coil of the other channel by the recording signal of one channel. Therefore, the crosstalk caused by multiple channels of secondary coils being wound around the same core is very small and can be practically ignored.
There is no deterioration of the recording signal flowing through b.

As described above, according to the present invention, multi-channel secondary coils are wound around the core of the same oscillation coil, and in the recording signal frequency band, the
Since the secondary impedance is selected to be sufficiently small compared to the composite impedance of the recording head and recording current equalizer, there is almost no crosstalk in the recording current between channels, and an inexpensive multi-channel tape recorder with a small number of components can be realized. There is an effect that can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a recording circuit of a conventional multi-channel tape recorder, FIG. 2 is a circuit diagram showing an embodiment of a recording circuit of a multi-channel tape recorder according to the present invention, and FIG. 3 is a circuit diagram showing an example of a recording circuit of a multi-channel tape recorder according to the present invention. FIG. 3 is a characteristic diagram showing the following impedance, magnetic head impedance, and recording current equalizer impedance characteristics. 10...Transformer, 10a...Primary coil, 7b,
10b...Secondary coil, 12a, 12b...Capacitor, 15...Resistor, 16...Transistor.

Claims (1)

[Claims] 1. In a multichannel tape recorder in which each of two or more channels has a respective recording input, an amplifier, a recording current equalizer, and a recording head, at least one for supplying a recording bias current to at least two or more recording heads. One oscillation circuit, at least two secondary coils for channels wound around the core of the oscillation coil of the one oscillation circuit, and a capacitor connected in parallel with each secondary coil, these A secondary coil and a capacitor are connected in series between the amplifier output of each channel and each recording head, and the impedance of the resonant circuit of the oscillation coil secondary coil and capacitor in the recording signal frequency band is A recording circuit for a multi-channel tape recorder, characterized in that the impedance of the recording current equalizer is selected to be sufficiently small compared to the combined impedance of the recording head and the recording current equalizer.