JPS63191487A - Recording amplifier for video tape recorder - Google Patents

Abstract

PURPOSE:To improve the SN ratio of a macro signal by providing a trap circuit which resonates at the difference in carrier frequency between two channels of an audio signal between a recording amplifier which records the audio signal and a rotary transformer corresponding to the audio signal. CONSTITUTION:The audio FM signal is recorded at the deep layer part of a magnetic tape T and a video FM signal is recorded at the surface layer part of the magnetic tape T. In this recording mode, a beat signal of 400 KHz is generated owing to the difference in frequency between the carriers of both R and L channels of the audio FM signal, but the trap circuit 10 resonates in this case to absorb and attenuate a beat signal. Consequently, the beat signal is prevented from interferring with and disturbing the frequency component of the nearly center part of the chroma signal converted to a low frequency of 629+ or -500 KHz to improve the SN ratio of the chroma signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a recording amplifier for a video tape recorder (hereinafter referred to as VTR) configured to record audio signals deep in the thickness direction of a magnetic tape. It is related to.

[Prior Art] Fig. 3 shows a state in which a head is attached to a rotating drum of a conventional VTR.
L) is a video head, (AR) and (AL) are audio heads, and the rotating drum (D) is, for example, 1.8
It is configured to rotate at a low speed of 00 rpm.

FIG. 4 is an electrical wiring diagram of a recording amplifier of a conventional VTR.
) and the above video head (VR) which is in charge of the video signal.
, (VL). Each of the above heads (AR), (A
L) , (VR), (VL) (7) Of which, (AR)
, (VR) is an odd field, and (AL) ,
The azimuth angle of each head is (VR): +6°, (VL): so that each head is in charge of (VL) or even field, and mutual crosstalk is eliminated.
-6°, (AR): +30'
, (AL): -30.

It is composed of

(2) is a rotary transformer, which is not shown,
Four transformers (2a), (2b), (2c) are created by housing the coils in four grooves formed in the rotating part ferrite core and the fixed part ferrite core, which are circular flat plates facing each other with a gap of about 50gn+ in between. , (2
d).

(3a), (3b), (3c), (3d) are four independent head amplifiers, (4a), (4b), (4
c) and (4d) are switches that connect the head amplifier (
One ends of the input parts 3a), (3b), (3c), and (3d) are grounded, and the rotary transformer (2) is driven in the recording mode. (5a), (5b) are the head amplifiers (3a), (3b), (3c), (3
A switch for switching the output of d) for each left and right channel (hereinafter referred to as R channel and L channel).By switching these switches (5a) and (5b), the audio signal and video signal are each converted into one continuous signal. do.

(Iia) and (6b) are the rotary transformers (2
) is a switch that operates to switch between recording mode and playback mode.It is open in recording mode and short-circuited in playback mode.

(7a) is an audio signal recording amplifier, and its input terminal (9a) is connected to the R channel and L channel FM.
When a modulated audio FM signal, ie, a HIFI signal, is applied, the rotary transformer (2) is driven.

(7a) is a video signal recording amplifier, and its input terminal (
When the R channel and L channel FM modulated video FM signals are applied to 9b), the rotary transformer (2) is driven.

(8a) is the output terminal for the audio FM signal, which amplifies the audio FM signal recorded on the magnetic tape by the head amplifiers (3a) and (3b), and as the switch (5a) changes for each field. , outputs one continuous audio FM signal.

(8b) is the video FM signal output terminal that outputs the video FM signal recorded on the magnetic tape to the head amplifier (3c).
) and (3d), and one continuous video FM signal is output as the switch (5b) is switched for each field.

Next, the operation of the above configuration will be explained.

First, as shown in FIG. 5(B), normal L channel and R channel audio signals are 1.3 MH on the L channel side, 1.3 MH on the 2 R channel side,
It is modulated into an FM signal having two carrier waves, such as 7MH2. The FM-modulated L-channel FM audio signal and R-channel audio FM signal are applied to the input terminal (9a). In this recording mode, the switches (4a) and (4b) are short-circuited and the switch (6a) is open, so the two transformers (2a) of the rotary transformer (2) are connected via the recording amplifier (7a). ,
(2b) is tried. These two transformers (2a
), (2b) to two audio heads (A
R) and (AL) are driven to record an audio FM signal on the magnetic tape.

Then, a normal video signal has a frequency shift of IMH2, as shown in FIG. 5(a), and has a frequency shift of 3.4MH2 to 4.
FM modulation with 4MH2 deviation F
M-change TAla degree signal, 3.58MH2±500KH
2(7)'y.

The color signal is separated into a low frequency converted color signal obtained by converting the color signal to 629KH2±500KH2, and both signals are applied to the input terminal (9b). During this recording mode, switches (4c) and (+d) are short-circuited, and switch (6b)
is open, so the two transformers (2c) and (2) of the rotary transformer (2) are connected via the recording amplifier (7b).
2d) is tried. These two transformers (2c)
, (2d) through two video heads (VR),
(VL) is driven, and a video signal is recorded on the magnetic tape.

And the above audio head (AR), (AL)
The azimuth angle of the video heads (VR) and (VL) is ±6° as shown in FIG. 5(a), and the azimuth angle of the video heads (VR) and (VL) is ±6° as shown in FIG. Figure (C
), the cap (gl) of the audio head (AR), (AL) is generally 1.2 pm, and the gap (g) of the video head (VR), (VL) is generally 0.2 pm.
35gm, and there is a relationship of gl>g. As a result, as shown in FIG. 5(c), the audio FM signal is first recorded in the deep part of the magnetic tape (T), and then the video FM signal including the chroma signal is recorded on the magnetic tape (T).
recorded on the surface layer. FIG. 5(d) is a diagram showing the above-described recording state from the surface of the magnetic tape (T).

Next, a brief explanation of how playback mode works is as follows.
All of the switches (4a) to (4d) are opened, and the switches (6a) and (6b) are short-circuited and grounded. As a result, the video FM signal recorded on the magnetic tape (T) is picked up by the heads (VR) and (VL), and then
Two transformers (2d) of the rotary transformer (2).

The signal is applied to head amplifiers (3c) and (3d) via (2c) and amplified. On the other hand, the audio FM signal is picked up by the head (AR) and (AL), and then
Two transformers (2a) of the rotary transformer (2),
The signal is applied to head amplifiers (3a) and (3b) via (2b) and amplified.

After that, the amplified video FM signal is sent to the switch (5
b), the amplified audio signal is switched field by field and outputted as one continuous signal from the output terminal (8b), and the amplified audio signal is switched field by field by the switch (5a), and is output as one continuous signal. It is output from the output terminal (8a) as.

[Problems to be Solved by the Invention] Conventional recording amplifiers for VTRs are configured as described above, so that audio signals, brightness signals, Care has been taken in the format to separate the chroma signal and reduce mutual interference.

However, as the image quality of VTRs has improved in recent years, it has become necessary to further reduce interference with audio FM signals that are recorded deep. This audio F
The interference from the M signal has a large adverse effect on the chroma signal processed by the AM signal, causing problems such as lowering the S/N of the chroma signal.

This invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a recording amplifier for a VTR that can improve the S/N of a chroma signal without degrading the performance of an audio FM signal. purpose.

[Means for Solving the Problems] A recording amplifier for a VTR according to the present invention includes a recording amplifier for recording an audio signal and a rotary transformer.
The present invention is characterized in that a trap circuit is provided that resonates with the difference in carrier wave frequency between two channels of audio signals.

[Function] According to the present invention, in the recording mode, the audio signal and the beat signal due to the difference in carrier frequency of the two R channels are absorbed and attenuated by the resonance of the trap circuit, so that the beat signal is transmitted through the rotary transformer. hand,
It is possible to prevent or reduce leakage of crosstalk to the video head. As a result, the beat signal due to the difference in carrier frequency between the two channels of the audio signal does not interfere with and disturb the frequency component of the chroma signal, and the S/N of the chroma signal is improved.

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is an electrical wiring diagram of a recording amplifier of a VTR according to an embodiment of the present invention.

(10) is a resonant trap circuit, which is an audio FM
Difference in carrier frequency between R and L two channels of signal, summary 1.7MH2-1,3MH2 = 400KH2 (7)
The resonant frequency is set and the audio FM
Two transformers (2a): a signal recording amplifier (7a) and a rotary transformer (2) for audio FM signals
, and the fixed coil (2b).

Since the other configurations are the same as those of the conventional example shown in FIGS. 3 and 4, the same reference numerals are given and detailed explanation will be omitted.

Next, the operation of the above configuration will be explained.

Audio FM signal recorded on magnetic tape (T)
A playback operation in which the video FM signal recorded on the magnetic tape (T) is picked up by two audio heads (AR) and (AL), switched for each field and output as one continuous signal, and is picked up by two video heads (VR).
), (VL), switching for each field and outputting as one continuous signal is the same as the above-mentioned conventional reproduction operation.

On the other hand, in the recording mode in which the audio FM signal is recorded in the deep layer of the magnetic tape (T) and the video FM signal is recorded in the surface layer of the magnetic tape (T), both the R and L channels of the audio FM signal are recorded. A beat signal of 400 KH2 is generated due to the difference in the frequency of the carrier waves, or at this time, the above beat signal is absorbed and attenuated by the resonance of the Yuri's trap circuit (10), so that the beat signal of 629 KHZ± The S/N ratio of the chroma signal can be improved by preventing the beat signal from interfering with and disturbing the approximately central frequency component of the chroma signal converted to a low frequency such as 500KH2.

Figure 2 shows the above situation using a video head (VR) or (
This is a club that exhibits frequency characteristics evaluated by VL).

In the above embodiment, the resonance trap circuit (10) is composed of two transformers (2a) including a rotary transformer (2).

(2b) is provided on the common line, but the above 2
They may be provided separately for each line of the two transformers (2a) and (2b).

[Effect of the invention] As described above, according to this invention, audio FM
The S/N ratio of the chroma signal can be improved by preventing the beat signal from interfering with the chroma signal due to the frequency difference between the carrier waves of both the R and L channels of the signal. This allows VT
This has the effect of contributing to improving R image quality.

[Brief explanation of the drawing]

FIG. 1 is an electrical wiring diagram showing a recording amplifier of a VTR according to an embodiment of the present invention, FIG. 2 is a club showing frequency characteristics, and FIG. 3 is a schematic diagram showing how a head of a conventional VTR is attached to a rotating drum. 4 are electrical wiring diagrams showing the recording amplifier of a conventional VTR, and FIGS. 5(a) to 5(d) are diagrams for explaining the state of recording into the deep layer and recording into the surface layer. . (1)...Rotating head, (2)...Rotary transformer, (2a) to (2d)...Transformer, (7a)...
- Audio signal recording amplifier, (7b)...Video signal recording amplifier, (10)...Trap circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A recording amplifier for a video tape recorder, which includes a recording amplifier that records audio signals in the deep part of the magnetic tape in the thickness direction, and a recording amplifier that records video signals in the surface part of the magnetic tape in the thickness direction. , wherein a trap circuit is provided between the recording amplifier for recording the audio signal and the rotary transformer corresponding to the audio signal, the trap circuit resonating with the difference in carrier frequency of each of the two channels of the audio signal. Recording amplifier for tape recorders.