JPS5923003B2 - Tape sensitivity display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for automatically detecting and displaying the sensitivity of a magnetic tape in a tape recorder.

There are various types of magnetic tapes currently on the market, such as normal type, ferri-chromium type, and chrome type, and even within the same type of tape, the recording sensitivity of the tape varies considerably depending on whether it is a popular type or a high-end type. You can see the difference. This difference in recording sensitivity is not much of a problem with a 2-head type deck, but with a 3-head type deck that allows simultaneous recording and playback and recording monitoring, if the gain of the recording amplifier is fixed, the adjustment tape and recording sensitivity will differ. When using tape, the source input level and the recording monitor level are different, and the level meter swings do not match, resulting in a deviation.
Also, when recording, the level of high frequency frequencies is increased and recorded.
Tape recorders with a built-in Dolby device attenuate the level of high frequencies during playback to reduce tape hiss and improve the signal-to-noise ratio.Due to the difference in recording sensitivity between standard tape and the tape used, recording and playback The Dolby levels do not match, and decoding is not performed accurately, resulting in deterioration of sound quality. Conventionally, the gain of the recording amplifier was made variable and the gain was adjusted manually using standard tape at the time of product shipment, or the user manually adjusted the gain using the tape being used. The disadvantage was that the latter could not be adjusted, and the latter was complicated to operate. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a tape sensitivity display device that automatically compensates for differences in recording sensitivity of magnetic tapes used and displays the recording sensitivity of the magnetic tape. .

In the present invention, the recording sensitivity of a standard tape serving as a reference is digitized in advance by an A/D converter and stored in a storage circuit, and when a reference signal is recorded and played back on the magnetic tape to be used, the playback output level is set as an A/D converter. D conversion is performed, and the difference is calculated by comparing with the above-mentioned digitized reference value.

The gain of the recording amplifier is automatically adjusted based on the above calculation result, and an output inversely proportional to the calculation result is output to the display section, thereby displaying it as tape sensitivity. The present invention will be explained in detail below with reference to an embodiment shown in the drawings.

In Fig. 1, 1 is an audio signal input terminal, 2 is a switch for switching between the audio signal and the reference signal, 3 is a variable gain circuit whose gain is changed stepwise by a control signal, and 4 is a corner frequency that can be changed by a control signal. 5 is a mid-range recording compensation circuit whose peaking amount is changed stepwise according to a control signal; 6 is a recording head; 7 is a playback head; 8 is a magnetic tape; 9 is a playback A signal amplifier, 10 a rectifier, 14 an A/D converter, 11 a control circuit, 12 an arithmetic comparison circuit, 13 a memory circuit, 16 a computer, 17
1 is a display circuit that outputs a voltage inversely proportional to the amount of compensation of the variable gain circuit 3; 18 is a display section of the indicator; and 15 is a reference signal generator whose frequency can be varied by a control signal.

FIG. 2 is a circuit diagram of one embodiment of the display circuit 17. In the magnetic recording/reproducing system shown in FIG. 1, before recording an audio signal, a 1 KHz reference signal is outputted from the reference signal generator 15 to compensate for the recording sensitivity of the tape and is recorded on the magnetic tape 8. Ru.

At this time, a standard control signal is output from the control circuit 11 to the variable gain circuit 3, the mid-range recording compensation circuit 4, and the high-frequency recording compensation circuit 5. The standard control signal is selected from standard tape data or the center value of the sensitivity compensation range. The recorded reference signal is reproduced by a reproduction head 7, passes through an amplifier 9 and a rectifier 10, and is converted into a digital signal by an A/D converter 14. The converted digital signal is input to an arithmetic comparison circuit 12 of a computer 16 and compared with a reference value stored in a storage circuit 13. Here, the gain compensation amount of the variable gain circuit 3 to compensate for the sensitivity of the tape and obtain the desired playback output is calculated, and this result is stored in the storage circuit 13 as control data and as a control signal in the control circuit. 11, variable gain circuit 3 and display circuit 17
is input. The display circuit 17 performs D/A conversion of a digital signal indicating the amount of gain compensation in a form that is inversely proportional to the amount of compensation.
The DC voltage is output to the display unit 18 and displayed as tape sensitivity. Thereafter, in the same manner, the reference signal of the reference signal generator 15 is selected for the middle range and the high range, and the middle range compensation circuit 4 compensates for the middle range, and the high range compensation circuit 5 compensates for the high range. It is possible to compensate for tape recording sensitivity and flatten recording/playback gain frequency characteristics. Here, as shown in FIG. 2, the display circuit 11 includes switching transistors Q, to Q4, weighting resistors R, 2R, 4R,
8R and bleeder resistance R.

and a base resistor. In the above configuration, 16 levels of display are possible using the 4-bit control signal input from the control circuit 11, and the amount of compensation can be, for example, (
0.0.0.0. ) 2 with good tape sensitivity,
All transistors Q, -Q4 are turned off, and the maximum voltage among the 16 levels is applied to the meter 18, indicating the maximum swing. (1.
1.1.1. ) 2 and the tape sensitivity is poor, transistors Q1 to Q4 are all turned on and the lowest voltage is applied to the meter 18, indicating the lowest deflection. In this way, tape sensitivity can be displayed by inputting data corresponding to the amount of gain compensation. As detailed above, according to the present invention, the difference in recording sensitivity of the magnetic tape used is automatically compensated for, and
By displaying the sensitivity of the magnetic tape, the tape sensitivity can be known at a glance.

Note that tape sensitivity compensation is performed using the magnetic tape's L. By performing this on both tracks of the R channel, L, . Needless to say, it is possible to display the tape sensitivity of both R tracks.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a circuit diagram of one embodiment of the display circuit used in FIG. 3... Variable gain circuit, 4... Mid-range recording compensation circuit, 5... High-range recording compensation circuit, 6...
... Recording head, 7... Playback head, 11.
...Control circuit, 12...Arithmetic comparison circuit,
13... Memory circuit, 14... A/D converter, 15... Reference signal generator, 17...
...Display circuit, 18...Indication meter, Q1~Q
4...Switching transistor, R, 2R,
4R, 8R... Weighted resistance.

Claims (1)

[Claims] 1. In a magnetic recording and reproducing apparatus having a control means for recording and reproducing a reference signal on a magnetic tape and automatically compensating the gain etc. of the recording system according to the magnetic tape, the amount of gain compensation by the control means is received as input and A tape sensitivity display device comprising: a display circuit that outputs a compensation amount as a tape sensitivity amount; and display means such as a meter driven by the output of the display circuit.