JPS642243Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention automatically changes the sensitivity of a recording signal level indicator meter (hereinafter referred to as the recording level meter) according to the MOL of the magnetic tape used, thereby providing an optimal recording signal. This invention relates to a tape recorder that allows level setting operations to be performed easily and accurately.

As is well known, magnetic tapes have different MOLs (that is, recording can be performed at a predetermined constant bias current) depending on the type (normal type, chrome type, metal, etc.) or the magnetic characteristics of each magnetic tape even if it is the same type of magnetic tape. (maximum output level) at which the third harmonic distortion in the reproduced signal obtained when the Therefore, it is desirable to set the recording signal level so that the maximum output level of the playback signal is equal to the MOL of the magnetic tape used, and only then can the dynamic range be fully utilized. death,
Moreover, recording can be performed in an optimal state without causing distortion due to an excessive recording signal level.

By the way, the recording level meter in a conventional tape recorder depends on the type of magnetic tape used,
Regardless of the magnetic characteristics, the tape recorder is always used at a constant sensitivity so that the tape recorder is instructed based on the preset absolute recording level. For this reason, when trying to record in the above-mentioned optimal state with such a conventional tape recorder,
The user should set the recording signal level higher than the standard value indicated by the recording level meter for magnetic tapes with MOL larger than the normal value, and set the recording signal level higher than the reference value indicated by the recording level meter for magnetic tapes with MOL smaller than the normal value. It was necessary to set the recording signal level to a low level. However, with this method, it is difficult to know the exact MOL of the magnetic tape used, and the recording level meter must be used at a position other than the predetermined indicated position. There were problems in that it was not only difficult to set the signal level, but also that the operation was difficult and troublesome.

This invention was made in view of the above circumstances, and aims to provide a tape recorder that allows easy and accurate setting of the optimum recording level according to the MOL of the magnetic tape used. It is something. In order to achieve this purpose, the tape recorder of this invention detects the MOL of the magnetic tape attached to the tape recorder body, and adjusts the sensitivity of the recording level meter according to the detected MOL. The feature is that the setting is automatically set to lower when the MOL is small and to raise when the MOL is small.

An embodiment of this invention will be described below with reference to the drawings.

The figure is a block diagram showing the configuration of an embodiment of this invention. The tape recorder shown in this figure amplifies the signal input to input terminal 1, encodes it to remove noise, and then outputs it to recording head 2.
The recorded signal level is indicated on the magnetic tape 3 via the recording head 5, and the signal reproduced via the reproduction head 5 is amplified and decoded to remove noise before being output. In the device configured to output from the terminal 6, the MOL of the magnetic tape 3 is measured and the sensitivity of the recording level meter 4 is automatically set based on the measurement result. In this embodiment, the magnetic tape 3 described above is
A microprocessor (hereinafter referred to as
This is done using a central processing unit such as MPU 7.

Each part of this embodiment will be described in detail below. first,
The MPU 7 responds to signals supplied via an operation unit 9 provided on an operation panel (not shown) of the tape recorder according to a program stored in a storage device 8 such as a read-only memory or a random access memory. It operates based on the motor and mechanical control unit 10, and drives and controls the magnetic tape running drive motors (not shown), mechanical parts, etc. in this embodiment, as well as controls other parts in this figure. It is something to do. 11 is a variable resistor that adjusts the signal level of the signal (recording signal) input to the input terminal 1, and the signal obtained at the sliding terminal of this variable resistor 11 is passed through the first buffer amplifier 12 to generate noise. The signal is supplied to an input terminal of a removal encoder (hereinafter referred to as NR encoder) 13 and also to an input terminal of a second buffer amplifier 14 . This buffer amplifier 14
is a monitor changeover switch 15 whose output will be described later.
It is possible to monitor the recording signal (source) by supplying the signal to the output terminal 6 via the output terminal 6, and the recording level meter 4
The recording signal level can be specified by being driven. The NR encoder 13 compresses the dynamic range of the output of the buffer amplifier 12 based on the output signal NR of the MPU 7 and manipulates the frequency characteristics (in the noise removal mode) or as it is (in other than the noise removal mode). ) is what is output. 1
6a and 16b are mode changeover switches which can be switched to the state shown by the solid line during normal recording and playback and to the state shown by the broken line during test mode by the output signal TS of the MPU 7.The test signal generator 17 is a 333Hz sine switch. An oscillator that generates a test signal consisting of waves, and an attenuator 18. This attenuator 18 is a variable whose resistance value is changed in stages based on the output signal TL (code signal) of the MPU 7. It consists of a resistance circuit 19 and a resistor 20. Then, the changeover switch 16
During normal recording and playback, the above-mentioned
The output of the NR encoder 13 is supplied to the attenuator 18, and in the test mode, the test signal generator 1
7 is supplied to an attenuator 18. Reference numeral 21 denotes a recording amplifier, which amplifies the output of the attenuator 18 and supplies it to the recording head 2 via a trap circuit 22. Reference numeral 23 denotes a bias oscillator that outputs a recording bias current during normal recording or test mode. is being supplied to.

Next, 26 is a reproduction amplifier that amplifies the output of the reproduction head 5, and the gain of this reproduction amplifier 26 is:
It is designed to be controlled by the output signal PG of the MPU 7. Further, the filter circuit 27, level detector 28, and A/D converter 29 are for detecting the signal level of the playback signal in the test mode, and 30 is for adjusting the output level of the playback signal during normal recording and playback. This is a variable resistor.
The output of the reproduction amplifier 26 is supplied via the changeover switch 16b to the variable resistor 30 during normal recording and reproduction, and to the filter circuit 27 during the test mode. Here, the filter circuit 27 uses the output signal FC of the MPU 7 to
A wideband filter characteristic that passes signals covering almost the entire frequency band of the reproduced signal outputted by the reproduction amplifier 26, and a signal component of only the vicinity of 1 kHz of the reproduced signal (i.e., the third harmonic component of the test signal mentioned above) is passed. It is possible to alternatively select a narrow band filter characteristic. Further, the level detector 28 converts the signal level of the output of the filter circuit 27 into a DC voltage according to the conversion ratio indicated by the output signal LC (code signal) of the MPU 7, and the A/D converter 29 converts the signal level of the output of the filter circuit 27 into a DC voltage. It converts the DC voltage output by the detector 28 into a corresponding digital quantity. The output of this A/D converter 29 is
Supplied to MPU7. On the other hand, variable resistor 3
The reproduced signal obtained at the sliding terminal 0 is supplied to the input end of a decoder 31 for noise removal (hereinafter referred to as NR decoder). This NR decoder 31
In accordance with the output signal NR of the MPU 7, the dynamic range of the reproduced signal is expanded by the amount compressed by the NR encoder 13, and its frequency characteristics are reversely manipulated by the amount manipulated by the NR encoder 13. It can be output afterward (when in noise removal mode) or directly as is (when not in noise removal mode). Next, monitor changeover switch 15
is to supply the output signal of the buffer amplifier 14 mentioned above to the output terminal 6 according to the output signal MO of the MPU 7 (the state shown by the solid line, when monitoring the source), or to supply the output signal of the NR decoder 31 to the output terminal 6 (the state shown by the broken line,
(when monitoring the playback signal). Next, the level detector 32 converts the signal level of the signal at the output terminal 6 into a corresponding DC voltage and outputs it, and the variable resistance circuit 33 connects the output terminal of the level detector 32 and the recording level meter 4. It is inserted between the MPU 7 and the input terminal, and its resistance value is changed according to the output signal SC (code signal) of the MPU 7, whereby the recording level is detected from the level detector 32. The meter driving current value supplied to the meter 4 is controlled.

In the above configuration, first the MOL of the attached magnetic tape 3 is measured and the measured
The operation when the sensitivity of the recording level meter 4 is automatically set according to the MOL, that is, the operation in the test mode will be explained. In this case, the user first attaches the magnetic tape 3 and then operates the
Instructs the MPU 7 to start operating in test mode. Then, the MPU 7 switches the changeover switches 16a and 16b to the test mode side (positions indicated by broken lines) using the signal TS, and also switches the switches 16a and 16b to the test mode side (positions indicated by broken lines) using the signal TS.
The resistance value of the variable resistance circuit 19 is set to the minimum value, the attenuation amount of the attenuator 18 is set to the maximum value, and then the magnetic tape 3 is started to run. As a result, a test signal consisting of a 333 Hz sine wave is recorded on the magnetic tape 3, and this test signal is reproduced via the reproduction head 5 and amplified by the reproduction amplifier 26. Here, the MPU 7 sets broadband filter characteristics to the filter circuit 27 using the signal FC,
After setting the conversion ratio of the level detector 28 to a predetermined value using the signal LC, the output of the A/D converter 29 is input and temporarily stored in the storage device 8. This means that the current output level of the reproduced signal is stored. Next, the MPU 7 converts the filter characteristics of the filter circuit 27 into a narrow band (1k
Hz), and the signal
After setting the conversion ratio of the level detector 28 to a value larger than the predetermined value by LC, the output of the A/D converter 29 is read and temporarily stored in the storage device 8. As a result, the output level of the third harmonic of the current reproduction signal is stored. here
The MPU 7 detects the output level of the reproduced signal, the output level of the third harmonic of the reproduced signal, and the level detector 28 at the time when these both output levels are read.
calculation is performed based on the conversion ratio of , the third harmonic distortion rate of the current reproduced signal is calculated, and it is determined whether this value is 3% or more. And if this 3
If the harmonic distortion rate is 3% or less, the MPU 7 uses the signal TL to lower the attenuation amount in the attenuator 18 by one step, that is, to set the recording level to a one step higher, and performs the same operation as described above. The same operation is performed, and the third harmonic distortion rate of the reproduced signal is calculated, and the calculated third harmonic distortion rate is 3.
% or more is determined again. and,
The MPU repeats the above operation until the 3rd harmonic distortion rate of the reproduced signal becomes 3% or more, and stores the output level of the reproduced signal as MOL at the time when the 3rd harmonic distortion rate reaches 3% or more. Record the amount in device 8.

Next, MPU7 uses the signal SC (code signal) to
The resistance value of the variable resistance circuit 33 is set so that the indicated position of the recording level meter 4 becomes a predetermined indicated position (for example, Odb) at the output level of the reproduction signal that matches the MOL.

As described above, according to this embodiment, when the user commands a test operation, the attached magnetic tape is
The MOL can be automatically measured and the position indicated on the recording level meter 4 corresponding to this MOL can be set so as to always match a predetermined indicated position. That is, in this example,
For magnetic tapes with a large MOL, the sensitivity of the recording level meter 4 is reduced (the indication of the recording level meter 4 is compressed), and for magnetic tapes with a small MOL, the sensitivity of the recording level meter 4 is increased. (The indication on the recording level meter 4 is enlarged).

In this embodiment, in the MOL calculation process, the effect of improving the dynamic range by the noise removal system consisting of the NR encoder 13 and the NR decoder 31 was not taken into account; however, in reality, the MOL calculation process It is desirable to perform calculations including this dynamic range improvement effect. In addition, in this example, the MOL of the magnetic tape used is actually measured as described above, but the MOL of the magnetic tape is
Since the approximate value is determined by the type of magnetic tape, it may be determined based on the output of a tape type changeover switch or the output of a tape type discrimination means using a sensing hole in a cassette half or the like. Also, when using this example,
When recording at the optimum recording level, MOL
For a plurality of magnetic tapes having different magnetic tapes, the signal level of the reproduced signal varies depending on the MOL.
Therefore, in order to keep the signal level of the reproduced signal constant regardless of the MOL, the signal PG output by the MOL7 must be used to adjust the level of the magnetic tape used.
It is only necessary to change the gain of the reproducing amplifier 26 according to the MOL.

As explained above, the tape recorder according to this invention has an MOL detection means for detecting the MOL of the attached magnetic tape and a meter sensitivity setting means, and instructs the recording signal level according to the detected MOL. Since the meter's sensitivity is automatically set to lower when the MOL is large and to increase when the MOL is small, the recording level meter's indicated position corresponding to the MOL of the attached magnetic tape is determined in advance. In this way, the user can adjust the recording level so that the indicated position (or deflection) of the recording level meter is always constant. The optimum recording signal level for the magnetic tape to be used can be set extremely easily and accurately.

[Brief explanation of the drawing]

The figure is a book diagram showing the configuration of an embodiment of this invention. 3... Magnetic tape, 4... Recording signal level indicator meter (recording level meter), 7... Microprocessor (MPU), 8... Memory device, 16a, 1
6b...Selector switch, 17...Test signal generator, 18...Attenuator, 27...Filter circuit, 2
8...Level detector, 29...A/D converter, 3
2... Level detector, 33... Variable resistance circuit.

Claims (1)

[Scope of utility model registration request] of the magnetic tape attached to the tape recorder body.
MOL detection means detects MOL, and based on the output of this MOL detection means, the sensitivity of the recording signal level indicator meter is lowered when the MOL is large and when the MOL is small.
A tape recorder characterized in that it is provided with a meter sensitivity setting means that automatically sets the sensitivity to increase when MOL is selected.