JP2834956B2 - Magnetic playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic reproducing apparatus for pre-amplifying a signal recorded on a magnetic tape in a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art High-definition television (eg, HDTV)
In order to digitally record this signal using a magnetic recording / reproducing apparatus (VTR), the data amount becomes about 1.2 Gbps, and multi-channel and high-density recording are essential conditions. Therefore, in order to reproduce a signal recorded on a magnetic recording medium such as a magnetic tape, it is necessary to provide a reproducing amplifier for pre-amplification in a rotating cylinder, and a magnetic reproducing circuit including the reproducing amplifier also performs high-frequency broadband, Further, the S / N must be improved.

A conventional magnetic reproducing apparatus provided in a rotary cylinder of such a VTR will be described with reference to FIGS. FIG. 6 is a block diagram showing a configuration of a conventional magnetic reproducing circuit, and FIG. 7 is a perspective view including a partial cross section of a rotary cylinder on which the magnetic reproducing circuit is mounted.

In FIGS. 6 and 7, a magnetic tape 1 is a magnetic recording medium for recording and reproducing multi-channel digital signals. The reproducing head 2 is a head for reading a signal of a track on the magnetic tape 1, and a plurality of reproducing heads 2 are provided on the outer peripheral portion of the rotary cylinder 3 via a head base 4 which is a head fixing base corresponding to each channel. As shown in FIG. 7, a printed circuit board 5 is mounted on the lower surface of the rotary cylinder 3, and a lead wire of the reproducing head 2 is connected to a connection terminal 6 of the printed circuit board 5.

The transmission line 7 is composed of the reproducing head 2 and the rotary cylinder 3
Is a line connecting the circuit section of the printed circuit board 8 attached to the upper surface of the printed circuit board. The transmission line 7 is wired through the hole of the rotary cylinder 3 and the printed board 8, and the connection terminal 9 is connected to the wiring pattern of the printed board 8. A plurality of reproduction amplifiers 10 shown in FIG. 6 are mounted on the printed circuit board 8. The reproduction amplifier 10 is a preamplifier that receives a reproduction signal from the reproduction head 2 and amplifies the signal, and is stored in a large number in a chip for surface mounting. The output of the reproduction amplifier 10 is given to the rotary transformer 12 via the connection terminal 11 of the printed circuit board 8.

In the magnetic reproducing apparatus thus constructed, each reproducing head 2 scans the magnetic tape 1 by helical scanning.
Read the signal of each track. This signal is transmitted on transmission line 7
, A reproduction amplifier 10 provided at each part of the printed circuit board 8
Is output to Next, the output of the reproduction amplifier 10 is output to the circuit section of the fixed printed circuit board of the VTR via the rotary transformer 12 provided below the rotary cylinder 3. The power of the reproduction amplifier 10 is supplied from a fixed power inverter via a rectifier circuit and another rotary transformer.

[0007]

In order to digitally record or reproduce a high-definition television signal using the magnetic reproducing circuit having such a configuration, multi-channel recording and high-density recording are indispensable conditions. The circuit must have a high frequency band. When the multi-channel reproducing heads 2 are provided on the rotating cylinder 3, respectively, the reproducing heads 2 are arranged at a constant pitch on the outer peripheral portion of the rotating cylinder 3, and the reproducing amplifier 10 of each channel is built in the same chip. In this case, the lengths of the signal lines of the reproducing head 2 and the reproducing amplifier 10 are different from each other. Due to this difference in the length of the signal line, a difference occurs in the frequency characteristics between the channels. Also, as the distance between the transmission lines 7 including the wiring patterns of the printed circuit boards 5 and 8 becomes longer, external noise is more likely to be hindered, crosstalk between channels increases, and the S / N deteriorates. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and the transmission line distance between a reproducing head and a reproducing amplifier is made substantially constant and the shortest distance is provided, thereby enabling the frequency characteristic of a circuit section to be improved. It is an object of the present invention to realize a magnetic reproducing apparatus capable of reducing the variation in S / N and improving the S / N.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a magnetic reproducing apparatus in which a magnetic reproducing circuit for reading a signal from a magnetic recording medium and amplifying the signal is mounted on a rotary cylinder, wherein each track of the magnetic recording medium is read. A plurality of reproducing heads for scanning and reproducing signals respectively; a fixed head for fixing the reproducing head and further fixed to a rotary cylinder; and a plurality of preamplifiers arranged on the fixed head and preamplifying reproduced signals from the reproducing head. A first amplifier circuit, and a second amplifier circuit for amplifying an output signal of the first amplifier circuit and providing the output to a rotary transformer. The output of the first amplifier circuit and the second amplifier circuit are provided. A signal line connecting the inputs of the circuit, wherein the power supply of the first amplifier circuit is also shared.

[0010]

According to the present invention having such features, the first amplifier circuit arranged near each reproducing head pre-amplifies the reproduced signal from the reproducing head. The second amplifier circuit supplies power to the first amplifier circuit, amplifies its output signal, and provides its output to a rotary transformer. When the reproduced signal is amplified in the rotating cylinder by such a method, the parasitic noise of the multi-channel signal can be reduced, and the frequency characteristics of the circuit can be made uniform.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the magnetic reproducing device of the present embodiment, and FIG. 2 is a perspective view including a partial cross section of a rotary cylinder on which the magnetic reproducing device of the present embodiment is mounted. FIG. 3 is a plan view of a printed circuit board to which a part of the magnetic reproducing circuit is attached.

1 and 2, a VTR for reproducing signals from the magnetic tape 1 is provided with a reproducing head 2, a rotary cylinder 3, and a head base 4 in the same manner as in the conventional example. Omitted. In FIG. 1, the output of the reproducing head 2 is connected to a printed circuit board 20 via a connection terminal 6. The printed circuit board 20 is a board attached to a part of the lower surface of the head base 4, and its outer shape is, for example, a rectangular board that conforms to the shape of the head base 4.

As shown in FIG. 3, on the printed circuit board 20,
Lead wires of the reproducing head 2 for the channels 1 to n are connected to, for example, lands. The first amplifier circuit 21 is connected to these lands via wiring lines. Each first amplifying circuit 21 is disposed adjacent to the respective read head 2 on the printed circuit board 2.
0 is provided for n channels and amplifies the read signal of the reproducing head 2. The output of the first amplifier circuit 21 is connected to one end of a transmission line 23 via a connection terminal 22 of the printed circuit board 20. As shown in FIG. 2, the other end of the transmission line 23 is connected to a connection terminal 25 which is a land of the printed circuit board 24.

The printed board 24 is a board mounted on the upper surface of the rotary cylinder 3 and holds various surface-mounted electronic components including the second amplifier circuit 26. FIG.
As shown in the figure, the second amplifier circuit 26 is
1 is a circuit for further amplifying the output signal, and its output is supplied to a connection terminal 27 provided at the center of the printed circuit board 24. This signal is supplied to a signal processing circuit provided on a fixed printed board of the VTR via a rotary transformer 28 provided below the rotary cylinder 3.

FIG. 4 is a circuit diagram showing an embodiment of a magnetic reproducing circuit centering on the first amplifier circuit 21 and the second amplifier circuit 26. In FIG. 4, the output of the reproducing head 2 is input to the base of the transistor Q1 via the capacitor C1. In the transistor Q1, a bias resistor R1 is connected between the base and the collector.
It is connected to the emitter of the transistor Q2 in the second amplifier circuit 25 via the transmission line 23.

The transistor Q2 is a transistor that supplies power to the transistor Q1 of the first amplifier circuit via its emitter and amplifies the output signal of the transistor Q1. The collector of the transistor Q2 has a load resistance R
2, and the base is connected to a common connection terminal of the bias resistors R3 and R4. This connection end is AC grounded by a capacitor C4. Next, the collector output of transistor Q2 is provided to amplifier A1. The amplifier A1 current-amplifies the signal of the transistor Q2 and supplies the signal current to the rotary transformer 28 via the connection terminal 27. The power supply Vcc is electromagnetically connected to a power supply inverter fixed to a VTR chassis via a rectifier circuit and a rotary transformer (not shown), and receives power supply.

FIG. 5 is a circuit diagram showing another embodiment of the magnetic reproducing apparatus. In the figure, the first amplifier circuit 21 is configured to include transistors Q3 and Q4 for differential amplification. That is, the lead wires of the reproducing head 2 are connected to the connection terminals 6a and 6b.
And transistors Q3 and C3 via capacitors C2 and C3.
Each is connected to the base of Q4. Transistors Q3, Q
4 has bias resistors R5 and R6, the differential outputs of which are applied to the emitters of the transistors Q5 and Q6 in the second amplifier circuit 26, respectively. The second amplifier circuit 26 is a circuit having transistors Q5, Q6, and an amplifier A2, and differentially amplifies the signal of the first amplifier circuit 21.

As shown in FIG. 5, transistors Q5 and Q6
Has load resistors R7 and R8 at the collector, respectively, and each base has bias resistors R11 and R1 via resistors R9 and R10.
2 common connection terminals. This connection end is AC grounded by a capacitor C5. The amplifier A2 is a circuit for differentially amplifying the collector outputs of the transistors Q5 and Q6. The signal of the amplifier A2 is connected to the connection terminal 2 as in FIG.
7. Output via the rotary transformer 28.

The operation of the magnetic reproducing apparatus thus configured will be described. In FIG. 1 and FIG. 2, first, when the rotary cylinder 3 rotates and scans the magnetic tape 1 wound therearound, the plurality of reproducing heads 2 read signals recorded on each channel of the magnetic tape, and read the signals. The signal is given to the first amplifier circuit 21. At this time, as shown in FIG. 3, the first amplifying circuit 21 is provided near each reproducing head 2, and thus pre-amplifies the reproduced signal without receiving surrounding noise.

The amplified signal is supplied to a second amplifier 26 via a transmission line 23. The signal level of the transmission line 23 is higher than the output level of the reproducing head 2, and the S / N does not deteriorate much due to noise mixed in from this path. In the method using a differential amplifier as shown in FIG.
And the common-mode noise induced between the connection terminal 6 and the transmission line 23 can be eliminated.

Next, this signal is further amplified by a second amplifier circuit 26 and applied to a rotary transformer 28 via a connection terminal 27. Then, a reproduced signal is transmitted from the rotary cylinder 3 to a transformer of a fixed cylinder (not shown) by electromagnetic coupling.

By providing the first amplifying circuit 21 in the vicinity of the reproducing head 2 in this manner, the length of the signal line is extremely shortened, and noise jumping and circuit oscillation factors are reduced. Further, even when the multi-channel first amplifier circuit 21 is provided as shown in FIG. 3, the length of the signal line can be made substantially equal in each channel, and the variation in the frequency characteristics of the circuit can be reduced.

Further, the second amplifier circuit 26 has an emitter input, and the transistors Q1 and Q2 of the first amplifier circuit 21
Alternatively, they are cascaded with the transistors Q3 and Q4. Therefore, the number of components of the first amplifier circuit 21 can be reduced, the power supply line to the first amplifier circuit 21 and the signal line can be shared, and the number of connections between the first and second amplifier circuits 21 and 26 can be reduced. Need only two.

[0024]

As described above, according to the present invention, the first amplifier circuits are provided in the vicinity of the reproducing head for the signals of each track of the magnetic recording medium, so that the coupling between the reproducing head and the amplifier circuit is achieved. Signal lines can be made the shortest distance, and the frequency characteristics of each signal line can be made uniform. Therefore, adverse effects such as noise jumping in the rotating cylinder, circuit oscillation, and crosstalk between channels are reduced, and a magnetic reproducing apparatus that is stable and has good S / N characteristics can be realized. Since the power supply of the first amplifier circuit is shared by the signal line between the first and second amplifier circuits, the number of connections between the first and second amplifier circuits must be two. Therefore, an effect is obtained that an amplifier circuit with a minimum number of connections and components can be configured.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a magnetic reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view including a partial cross section of a rotary cylinder on which the magnetic reproducing device of the present embodiment is mounted.

FIG. 3 is a plan view of a printed circuit board to which a part of the magnetic reproducing apparatus of the embodiment is attached.

FIG. 4 shows first and second magnetic reproducing devices according to the present embodiment.
FIG. 3 is a circuit diagram (part 1) illustrating a configuration example of the amplifier circuit of FIG.

FIG. 5 shows first and second magnetic reproducing apparatuses according to the present embodiment.
FIG. 3 is a circuit diagram (part 2) illustrating a configuration example of the amplifier circuit of FIG.

FIG. 6 is a block diagram illustrating a configuration example of a conventional magnetic reproducing apparatus.

FIG. 7 is a plan view of a printed circuit board to which a part of a conventional magnetic reproducing device is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 2 Reproducing head 3 Rotating cylinder 4 Head base 6, 22, 25, 27 Connection terminal 21 First amplifier circuit 23 Transmission line 26 Second amplifier circuit 28 Rotary transformer 20, 24 Printed circuit board

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-286402 (JP, A) JP-A-4-209303 (JP, A) JP-A-1-232502 (JP, A) JP-A-58-58 205314 (JP, A) JP-A-59-63008 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/02

Claims (2)

(57) [Claims] 1. A magnetic reproducing apparatus in which a signal from a magnetic recording medium is read and a magnetic reproducing circuit for amplifying the signal is mounted on a rotary cylinder, and scans each track of the magnetic recording medium to reproduce the signal. A plurality of reproduction heads, a head fixing base for fixing the reproduction head, and further fixed to a rotating cylinder; a plurality of first heads arranged on the head fixing base for pre-amplifying a reproduction signal from the reproduction head. An amplifier circuit; and a second amplifier circuit that amplifies an output signal of the first amplifier circuit and supplies the output to a rotary transformer. The output of the first amplifier circuit and the second amplifier circuit And a power supply for the first amplifier circuit is also shared by a signal line connecting the inputs of the magnetic reproducing apparatus. 2. The differential amplifier circuit according to claim 1, wherein the first amplifier circuit is a differential amplifier circuit that receives a signal from each output terminal of the reproducing head as an input, and outputs two difference signals output from the first amplifier circuit. 2. The magnetic reproducing apparatus according to claim 1, wherein the power supply of the first differential amplifier circuit is shared by the dynamic output line.