JPS5928509Y2 - magnetic recording and playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device equipped with a calibration oscillator and capable of calibrating frequency characteristics.

Generally, when calibrating the overall frequency characteristics of the recording and playback system of a magnetic recording and playback device, a low frequency (for example, 400Hz) is used.
) and a high frequency (for example, 10 KHz), two or more frequency signals are recorded and played back at the same time, and their respective playback levels are adjusted to be approximately equal to adjust the frequency characteristics.

And the recording of the general magnetic recording and playback device shown in Fig. 2,
As is clear from the overall frequency characteristics of the reproduction system, 40
The input level that provides a flat frequency response from 0Hz to 10KHz is -20dB or less (see curve A), -10
In the characteristic curve B of dB and the characteristic curve C of OaB, the characteristics are unbalanced between low and high frequencies, so in order to perform calibration without error, the signal level from the calibration oscillator is selected to be about 20 dB, and this signal is being recorded and played back.

However, when recording at a low level of around -20dB,
It is difficult to read the reproduced signal level on a level meter.

As a countermeasure to this, the amplification degree of the meter amplifier was increased when calibrating the frequency characteristics.
It becomes easier to read by obtaining the OdB fluctuation.

However, in this case, if the level meter is capable of displaying a wide range, for example, with a meter that can display -40 dB, the apparent -40 dB point is actually -60 dB.

Then, as can be seen in Figure 2, the normal meter indication range X, +10 dB to -40 dB, deviates from the noise level (curve D), but during calibration, the normal meter indication range X is amplified by 20 dB, and 10 dB to -40 dB. If you actually specify a range Y of 60 dB, and there is noise in the range Y from -40 dB to -60 dB, therefore, if you turn down the variable resistor for adjusting the recording level, only the noise level will be displayed on the meter. This will cause inconvenience.

In view of these conventional drawbacks, the present invention is designed to prevent noise from being displayed on the level meter even if the variable resistor for adjusting the recording level is turned down during calibration.

An embodiment of the present invention will be described below with reference to FIG. 1. In FIG. 1, 1 is a source input terminal to which signals etc. from a microphone are supplied, 2 is a calibration oscillator, 3 is a source/test selector switch, 4 is a variable resistor for adjusting the recording level, 5 is a recording amplifier, and 6 is a recording head.

Then, either the source signal from the source input terminal 1 or the test signal from the calibration oscillator 2 is selected by the source/test selector switch 3, amplified by the recording amplifier 5, and supplied to the recording head 6. (not shown).

Next, 7 is a playback head, 8 is a playback amplifier, 9 is a tape-source monitor changeover switch, 10 is an output terminal, 11 is a meter drive amplifier, 12 is a level meter, and 13 is a switch to increase the sensitivity of the level meter 12. .

The signal recorded on the magnetic tape via the recording head 6 is reproduced by the reproduction head 7 which is activated at the same time as the recording head, amplified by the reproduction amplifier 8, and transmitted through the tape contact T of the tape source monitor switch 9. is supplied to the output terminal 10 for reproduction, and is also supplied to the meter amplifier 1.
1, the playback level is displayed by a level meter 12.

In addition, when checking the recording level, by setting the tape source monitor changeover switch 9 to the source contact S side, the recording signal from the recording amplifier 5 is supplied to the output terminal 10 via the switch 9, and the meter amplifier It is also supplied to a level meter 12 through 11, so that the level can be displayed.

Next, let us explain the case when trying to calibrate the frequency characteristics.
First, the source test O8C selector switch 3 is switched to the calibration oscillator 2 side.

Then, the test signal from the calibration oscillator 2 is sent to the recording amplifier 5 through the recording level adjustment variable resistor 4. The signal is recorded on a magnetic tape through a recording calibration variable resistor 14.

Further, the level of the test signal is indicated to a level meter 12 via a meter amplifier 11 via a source contact S of a tape source selector switch 9.

At this time, the switch 13 is closed, and the sensitivity of the meter is increased by 20 dB so that the -20 dB level supplied to the level meter 12 appears to indicate an O dB scale.

Then, the recording level adjusting variable resistor 4 is adjusted so that the level meter 12 indicates OdB.

As a result, the signal before recording becomes -20 dB.

Next, the tape source selector switch 9 is switched to the tape contact T side, and the recorded test signal is played back by the playback head 7.
The signal is amplified by a reproducing amplifier 8, and a level meter 12 is driven through a tape source changeover switch 9 and a meter amplifier 11.

The recording calibration variable resistor 14 is adjusted so that the level meter 12 indicates OdB at this time, and the frequency characteristics are calibrated.

At this time, if the variable resistor 4 for adjusting the recording level is narrowed down, the test signal will no longer be recorded and only noise will be displayed on the level maker 12.

Therefore, in this actual case, even if an arbitrarily set resistor 15 is inserted between the ground side E and the ground 0 of the variable resistor 4 for recording level adjustment, and the variable resistor 4 for recording level adjustment is fully throttled, The test signal component does not become zero due to the resistor 15, and the input can be set within the zero range of approximately ±6 dB from the apparent O dB using the variable resistor 4 for adjusting the recording level.

Note that a switch 16 for short-circuiting the resistor 15 is connected in parallel to the resistor 15.

As a result, when calibrating the frequency characteristics, the switch 16 is closed when the recording level variable resistor 4 is fully turned down, so that the input becomes zero.

Also, when the source test selector switch 3 is switched to the oscillator 2 side, the switch 16 is opened to activate the resistor 15, and at the same time, the switch 13 is also closed to increase the sensitivity of the meter. , these 3
Although it is convenient to have the switches 3, 13, and 16 interlocked, they may be switched individually without interlocking.

As explained above, according to the magnetic recording and reproducing device of the present invention, even when the variable resistor for adjusting the recording level is fully turned off during frequency calibration, only the noise level is not displayed on the level meter, unlike the conventional method. A simple modification of inserting a resistor into something and shorting it or activating it can have the great effect of making it possible to perform accurate calibration with fewer errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a comprehensive frequency characteristic diagram of the recording and reproducing system of a general magnetic recording and reproducing device. 1... Source input terminal, 2... Calibration oscillator, 4... Variable resistor for recording level adjustment,
6... Recording head, 7... Playback head, 11... Meter 1 driving amplifier, 12...
... Level meter, 13 ... Sensitivity selection switch, 16 ... Switch.

Claims (1)

[Scope of utility model registration request] A frequency that has an oscillator that generates a test signal, records the test signal from the oscillator on a magnetic tape, reproduces it, and calibrates the frequency characteristics while checking the reproduced signal with a level indicator. A magnetic recording and reproducing device equipped with a characteristic calibration device, which is provided with a means to increase the sensitivity of a level indicator only during calibration, and a grounding terminal of a variable resistor for adjusting a recording level that sets the recording level of a test signal only during calibration. A magnetic recording/playback device constructed by inserting a resistor between the ground and the ground.