JPS6043563B2 - tape recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape recorder, and an object thereof is to be able to automatically set an optimum recording level.

When a conventional tape recorder attempts to record, it either monitors the recording level with a meter and adjusts a variable resistor to an appropriate level, or uses an automatic gain control device called M° to control the input level. The recording level was automatically adjusted according to the average value of the signal.

However, the adjustment method using a variable resistor is not only cumbersome to operate, but also requires reading the set level based on the positional relationship between the mark provided on the knob of the variable resistor and the scale surrounding it. Reading the level was extremely troublesome and the display was vague.

Further, the adjustment method using M° C. has drawbacks such as the dynamic range of the input signal being compressed when recording and the set level not being displayed at all. Therefore, the present invention solves these conventional drawbacks and provides a tape recorder that automatically sets the optimum recording level by simply operating an automatic setting switch. explain. Figure 1 schematically shows the circuit configuration for automatic level setting, in which 1 and 2 are the input and output terminals of the recording signal, respectively, and 3 is the gain between input terminal 1 and output terminal 3. This is a gain control circuit that changes the

4 is a level detector which functions to detect the level of the signal applied to the input terminal 1;

5 is a maximum value holding circuit, which is detected by the level detector 4.
The gain control circuit 3 functions to hold the maximum value among the levels and supply a control signal corresponding to the maximum value to the gain control circuit 3.

Reference numeral 6 denotes a time setting circuit which generates a pulse having a predetermined time width by operating an automatic setting switch 7 and supplies it to the maximum value holding circuit 5.

36 is a display that displays the operating state of the time setting circuit 6, and 41 is a display drive circuit that receives the output of the maximum value holding circuit 5 and causes the setting level display 43 to perform a display operation.

In the above configuration, when the operator presses the automatic setting switch 7, the time setting circuit 6 is immediately driven and generates a pulse with a time width corresponding to a predetermined setting time. It will be done. Maximum value holding circuit 5
holds the maximum level detected by the level detector 4 within the time set by the time setting circuit 6, and sends a corresponding control signal to the gain control circuit 3 and the display drive circuit 4.
Supply to 1. Therefore, the gain control circuit 3 is controlled to a gain determined by the maximum level of the input signal within a certain period of time, and this level is displayed on the display 43. Further, the output terminal 2 is connected to the recording amplifier of the tape recorder, and a recording current is supplied to the magnetic head, so that the maximum holding voltage measured during the time determined by the time setting circuit 6 is is set to control the gain control circuit 3 so that, for example, the peak of the input signal is recorded at the maximum recording level of the tape.

By doing this, the maximum level of the input signal is recorded at the maximum recording level of the magnetic tape, and other signal levels are recorded below the maximum recording level.

Therefore, the input signal is recorded without being subjected to saturation distortion of the magnetic tape, and without compressing the dynamic range of the input signal. The recording level can be set by a one-touch operation of simply pressing the automatic setting switch 7, making the operation extremely easy compared to conventional recording level setting. Here, the time setting circuit 6 enables automatic recording level setting with one-touch operation.
This is based on an experimental result that the maximum value measurement time determined by 2 is sufficient for most input signals.

FIG. 2 is a diagram showing experimental results in which the relationship between the maximum value measurement time and the measured maximum level is plotted for three types of input sources.

When the source is A (speech), the maximum level is saturated in about 4 seconds. This shows that even if the maximum value measurement time is longer than 4 seconds, the maximum value hardly changes. When the source is B (popular music), it saturates in about 7 seconds, and when the source is C (popular music), it saturates in about 6 seconds. Therefore, it can be said that it is sufficient to set the maximum value measurement time to about 8 to 2 or more, except for special sources. On the other hand, from the viewpoint of the operator's usability, it is considered that the shorter the measurement time, the better, and therefore it is preferable to set the time width of the time setting circuit 6 to about 5 to m seconds.

FIG. 3 shows a more specific embodiment of the main parts of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 3, the recording level can be set by a one-touch operation by simply pressing the automatic setting switch 7. When the automatic setting switch 7 is shorted, the monostable multivibrator 32
is driven, one pulse with a time width corresponding to the maximum value measurement time explained in FIG. 1 is generated, and the AND gate circuit 1
2 and 13. The input signal applied to the input terminal 1 is converted by the peak detector 9 into a DC voltage according to the peak level of the signal, and this is converted by the analog-digital (AD) converter 11 into a number of pulses, which is a digital signal. Ru. During the measurement period, that is, when the monostable multivibrator 32 is driven via the inverter 33 and is generating pulses, one output Q of the monostable multivibrator 32 is set to RHJ, and the other output O is set to R.
Make it LJ.

Therefore, one input of the AND gate circuits 12 and 13 is set to RHJ through the 0R gate circuit 34, and the pulse from the AD converter 11 passes through the AND gate circuit 12.
It is applied to the counting terminal (IN) of the digital counter 8 via the 0R gate circuit 37, and the pulse generator 1
A clear pulse from 0 is also applied to the clear input terminal (CL) of the digital counter 8 through the AND gate circuit 13. A digital counter 8, a latch circuit 1, and a comparator 15 constitute the maximum value holding circuit 5 shown in FIG.
It functions to detect and hold the maximum value among the number of pulses corresponding to the input level successively sent from the D converter 11.

That is, the maximum value holding operation is performed digitally. The digital output is given to the gain control circuit 3 as a control signal.
The gain control circuit 3 includes a plurality of resistor attenuators including analog switches, and each resistor attenuator is controlled to be attenuated or not attenuated according to the digital output given from the latch circuit 14, and the total amount of attenuation is determined. be done. Therefore, the attenuation amount is set in accordance with the maximum human power during the maximum value measurement period during which the monostable multivibrator 32 is generating pulses. That is, when the maximum human power is large, the attenuation amount is set to be large. If the operator wishes to extend the measurement period of the maximum input level value (for example, when the input source is special such as classical music), instead of pressing and immediately releasing the automatic setting switch 7, Just hold it down for as long as you want.

While the automatic setting switch 7 is kept pressed, the output of the inverter 33 is RH, the pulse generation operation of the monostable multivibrator 32 is stopped, and its Q output is 1.
Even if it becomes low, 1H is applied to one input of the 0R gate circuit 34.
Since J is added, RHJ is applied to one input of AND gate circuits 12 and 13, and pulses from AD converter 11 and pulse generator 10 continue to be sent to digital counter 8. When the automatic setting switch 7 is released, the output of the inverter 33 becomes 1LJ, and the digital counter 8
The input to the digital counter 8 is cut off by the AND gate circuits 12 and 13, and the digital counter 8 does not perform counting, but continues to hold the count value counted during the period. Therefore, the attenuation amount of the gain control circuit 3 is also maintained at a value corresponding to the maximum human power level set during the measurement period. The peak detector 9 is a circuit that detects the peak level of an input signal, and is usually composed of an absolute value circuit and a smoothing circuit with a short time constant.

The pulse generator 10 generates a clock pulse for the pigeon converter 11 and a clear pulse for clearing the digital counter 8 every time it is sampled by the AD converter 11. This clear pulse is generated in synchronization with the AD converter 11 sampling at regular intervals, and immediately before the pigeon converter 11 converts the sample value into a pulse number and outputs it. In short, the clear input terminal of digital counter 8 (
The clear pulse applied to CL) clears the count value of the digital counter 8 to O so as not to accumulate the previous count value, and prepares it for counting corresponding to the next sample value. Therefore, the digital counter 8 outputs a count value corresponding to a sample value of the peak level of the input signal every fixed period. The digital counter 8, latch circuit 14 and comparator 15 are the maximum value holding circuit 5 in FIG.
In the non-latched state, the latch circuit 14 outputs the count value of the digital counter 8 as it is, and in the latched state, it functions to maintain the previous value regardless of the input.

The comparator 15 is the count output Al of the digital counter 8.
, A2, A3, A4 and the outputs of the latch circuit Bl, B2, B
3 and B4, and outputs a pulse that satisfies the relationship A>B, and this pulse unlatches the latch circuit 14 to make it into a non-latched state, and outputs the output of the digital counter 8 to the latch circuit 14. As is clear from the above explanation, the latch circuit 14 and the comparator 15 output the latch only when the count outputs Al, A2, A3, and Al of the digital counter 8 are respectively larger than the previous latch outputs Bl, ■, B3, and B4. Update and hold the output when it is small.

Therefore, the maximum value of the count values sequentially sent from the digital counter 8 is obtained as the output of the latch circuit 14. The gain control circuit 3 is composed of a four-stage resistance attenuator and an analog switch.

Resistors 16 and 17, analog switch 18, and buffer amplifier 19 constitute a first-stage resistance attenuator, and analog switch 18 is cut off when output B1 of latch circuit 14 applied to its gate is in conduction state JL when it is RHJ. As a result, when the output 2 of the latch circuit 14 is RH, the first stage resistor attenuator exhibits an attenuation state due to the voltage division ratio of the resistors 16 and 17, and ? When is RLJ, it is in a non-damped state. The buffer amplifier 19 serves to prevent mutual influence between the first and second stage resistive attenuators. Similarly, resistance 20, 21
and analog switch 22 and buffer amplifier 23 are 2
Resistors 24, 25, analog switch 26, and buffer amplifier 27 form the 3rd stage resistance attenuator, and resistors 28, 29, analog switch 30, and buffer amplifier 31 form the 4th stage resistance. The resistor attenuators from the first stage to the fourth stage are connected in series to form a gain control circuit 3, and each resistor attenuator has a different amount of attenuation in its attenuation state. ,
For example, it is set to 1 dB, 2 dB, 4 dB, and 8 dB. It has already been mentioned that when the measurement period ends, the AND gate circuits 12 and 13 enter the blocking state, but in this state, when the operator presses the manual setting switch 40, one counting pulse is generated every time the operator presses the manual setting switch 40. 39 and applied to one input of the N1 gate circuit 38. The output of the N1 gate circuit 35 is connected to the other input of the AND gate circuit 38, and RHJ is applied thereto. In other words, after the automatic setting is completed, the O output of the monostable multivibrator 32 is RHJ, and the automatic setting switch 7 is not pressed, so the both power of the AND gate circuit 35 is R.
This is because it becomes Hj. Therefore, the counting pulse from the counting pulse generator 39 is applied to the AND gate circuit 38, passed through the 0R gate circuit 37, and applied to the counting power of the digital counter 8 to perform counting. The gain of is changed. Although not shown in the figure, the latch operation of the latch circuit 14 is not performed during this manual setting. In addition, manual setting switch 40
By providing a direction (counting) and a DOWN direction and adding them to the UP and DOWN inputs of a digital counter, respectively, the set level can be moved in either direction up or down from the automatically set level. Furthermore, a display is provided to distinguish between the measurement period and the period after automatic setting (manual setting period). Reference numeral 36 denotes a two-color light emitting diode constituting the display device, which emits red light when current flows through Dl6, and green light when current flows through Dl7, for example.

As already explained, the output of the 0R gate circuit 34 is RH! during the measurement period. The output of the AND gate circuit 35 becomes RH after the automatic setting is completed.

Therefore, if you connect these outputs so that current flows through the resistors R7 and R8 to the light emitting diodes Dl6 and Dl7, the light will turn red during the measurement period, and then automatic setting will be completed and manual setting will be possible. When it is, a green light will emit,
It would be very convenient to place this on the panel surface of the tape deck. Note that this display is not limited to two-color light emitting diodes; it can also be differentiated by lighting the light emitting diode only when one mode is selected, or by having it blink during the measurement period and turn it on continuously after the settings are complete. Easy to implement. Furthermore, a display drive circuit so-called decoder 41,
The setting ν bell (attenuation amount) display 43 will be explained as follows.
The decoder 41 has a BCDtOdecimal signal connected to the output B2, formula, and B4 of the latch circuit 14 in order to display the attenuation setting value of the gain control circuit 3 on the attenuation display 43.
It is composed of a decoder 42 and a switching circuit 44 connected to the output B1 of a minimum resistance attenuator (for example, 1 dB) to the analog switch 18.

When the output of the latch circuit 14 is RH, the switching element Q1 is turned on and the switching element Q2 is turned off by the inverter Q3. On the contrary, latch circuit 1
When the output of the switch 4 is 1LJ, the switching element Q1 is in the cutoff state and the switching element Q2 is in the conduction state. Switching element Q
When Q1 is in a conductive state (Q2 is in a cutoff state), the power supply VO. The light emitting diode D of the attenuation amount display 43 is connected through the resistor r1.
l, zhi. , D5, ... If the conditions for lighting Dl5 are met, and vice versa, D. , D2, D4, . . . , the lighting conditions for Dl4 are satisfied. Then, the other output B2 of the latch circuit 14
, B3, B4, the light emitting diodes Dl, D3, . . . , Dl under the above-mentioned lighting condition are
5 (or D.

, D2, . . . , Dl4), one of the eight lighting conditions is satisfied. In other words, the output 8 of the latch circuit 14 and Bl, , B3
, B4, one light emitting diode in one hat is lit. That is, read the attenuation amount of the gain control circuit 3, and set each resistor attenuator to 1.
If dB, 2dB, 4dB, aB, one light emitting diode D. ,Dl,...,Dl5, 0c1B~1
5c1B can be displayed. Furthermore, the configuration of the apparatus of this embodiment will be explained using FIG. 4.

In Figure 4, the automatic level setting circuit shown in Figure 3 is
It is shown as one block 50, and only the necessary parts are shown in the block. When the automatic setting switch 7 is turned on, the output of the 0R'' gate circuit 34 is connected to the inverter 33,
A monostable multivibrator 32 maintains RH during the level detection period.

When the 0R gate circuit 34 becomes RHJ, the switching element O becomes conductive via the resistor RlO, and current flows from the power source ■Cc to the relay 47 via the resistor R9.

The AGC switch 48 is closed by the relay 47, and the AGC circuit 49 provided in the recording amplifier 45 is operated, and the signal applied from the input 1 is applied to the gain control circuit 3, no matter what the setting value is. Even if the signal level of output 2 becomes excessive, the recording current applied to the recording head 46 via the recording amplifier 45 remains within the appropriate recording level.
It is controlled by an AGC circuit 49. After level detection, 0
The output of the R gate circuit 34 becomes 1L, the switching circuit Q4 is cut off, no current flows through the relay 47, the AGC switch 48 is opened, and the AGC circuit 49 is disconnected from the recording amplifier 45.

At the same time, the signal applied from input terminal 1 is controlled to an appropriate level by automatic level setting circuit 50 and output to output terminal 2, so that proper recording can be performed. Figure 5 is Figure 3,
This figure shows the external appearance of a tape recorder incorporating the circuit shown in FIG. 4, in which 51 is a cassette loading section, 52 is a group of tape running operation buttons, and 53 is a digital level meter for displaying the recording and playback level.

The attenuation amount indicator 43 is a light emitting diode D as shown in the figure. -Dl
The manual setting switches 40 are divided into an UP switch 40a and a DOWN switch 40b. Further, a display 36 made of two-color light emitting diodes is provided within the knob of the automatic setting switch 7, so that operations and display can be performed in one place. As explained above, the tape recorder of the present invention. Since the recording level can be set with one-touch operation, the operation is extremely simple compared to conventional level settings, and the level setting corresponding to the maximum input signal level can be achieved, making it possible to set the recording level with a single touch. Not only is it possible to set a high-quality recording condition that does not cause distortion, but when the recording level is being set, a normal automatic gain control circuit is automatically activated to stabilize the recording level. Therefore, the difference in the recording level during and after the setting operation is eliminated, and distortion-free recording is made possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an example of the present invention, FIG. 2 is a diagram showing experimental results for explaining the embodiment of the present invention, and FIG.
FIG. 4 is a circuit diagram of a specific embodiment of the present invention, and FIG. 5 is a perspective view showing the appearance of the embodiment of the present invention. 1...Input terminal, 2...Output terminal, 3
... Gain control circuit, 4 ... Lebel detector, 5 ... Maximum value holding circuit, 6 ... Time setting circuit, 7 ...... Automatic setting switch, 8...
...Digital counter, 9...Peak detector, 10...Pulse generator, 11...A
D converter, 12, 13...AND gate circuit, 14...Latch circuit, 15...Comparator, 32...Monostable multivibrator, 34,
37...0R gate circuit, 35,38...A
ND gate circuit, 36... two-color light emitting diode,
39...Counting pulse generator, 45...Recording amplifier, 47...Relay, 48...
AGC switch, 49...AGC circuit.

Claims (1)

[Claims] 1. A gain control circuit disposed in the recording signal transmission path, a level detector for detecting the signal level of the recording signal transmission path, an automatic setting switch operated when automatically setting the recording level, and a control circuit for detecting the signal level. a time setting circuit for setting a time for measuring the maximum value; and a maximum value holding circuit to which the output signal of the level detector is input and capable of holding the maximum level during the time set by the time setting circuit. , comprising a recording amplifier, an automatic gain control circuit for automatically controlling the gain of the recording amplifier, and a switch means for controlling the operation of the automatic gain control circuit, the time setting circuit being controlled by the operation of the automatic setting switch. In order to automatically set the gain of the gain control circuit according to the maximum input level to the recording signal transmission path during a set time, the gain control circuit is controlled by the output of the maximum holding circuit, and the gain control circuit is controlled by the output of the maximum holding circuit. A tape recorder characterized in that the switch means is operated to operate the automatic gain control circuit only when the time setting circuit is in operation.