JPS6113302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape recorder, and an object of the present invention is to automatically set an optimum recording level and display the set level, and also set the recording mute time to the set level. The purpose is to enable display on the display unit.

With conventional tape recorders, when attempting to record, the recording level is monitored with a meter and adjusted to an appropriate level by adjusting a variable resistor, or by an automatic gain control device called AGC. 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 a mark on the knob of the variable resistor and a scale around it. It was very difficult to read and the display was vague.

Furthermore, the adjustment method using AGC has drawbacks such as the dynamic range of the input signal being compressed and recorded, and the setting level not being displayed at all.

Therefore, the present invention solves these conventional drawbacks, and by simply operating the automatic setting switch, the optimal recording level is automatically set and displayed, and the recording mute time can also be displayed on this display. The present invention provides a tape recorder, and one embodiment thereof will be described below with reference to the drawings.

Figure 1 schematically shows the circuit configuration for automatic level setting. In the figure, 1 and 2 are the input terminal and output terminal of the recording signal, respectively, and 3 is the input terminal 1.
This is a gain control circuit that changes the gain between the output terminal 3 and the output terminal 3. 4 is a level detector which functions to detect the level of the signal applied to the input terminal 1; Reference numeral 5 denotes a maximum value holding circuit, which functions to hold the maximum value of the levels detected by the level detector 4 and supply a corresponding control signal to the gain control circuit 3. Reference numeral 6 denotes a time setting circuit which generates a pulse of a constant time width by operating an automatic setting switch 7 and supplies it to the maximum value holding circuit 5. 36 is a display for displaying the operating state of the time setting circuit 6;
Reference numeral 41 indicates a display drive circuit that receives the output of the maximum value holding circuit 5 and displays the set level display 43, 45 indicates a recording mute switch, and 51 indicates a counter that operates in connection with the mute operation of the recording mute switch 45. A pulse generator 54 counts the output pulses of the pulse generator 51 to control the display drive circuit 41 and displays the setting level display 43.
This is a counter to display the recording mute time.

In the above configuration, when the operator presses the automatic setting switch 7, the time setting circuit 6 is immediately driven.
Pulses with a time width corresponding to a predetermined set time are generated, and these pulses are applied to the maximum value holding circuit 5. Maximum value holding circuit 5 is level detector 4
Among the detected levels, the maximum one within the time set by the time setting circuit 6 is held, and a corresponding control signal is supplied to the gain control circuit 3 and the display drive circuit 41. 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.

Also, when the recording mute switch 45 is operated to mute the recording signal, the output of the pulse generator 51 is counted by the counter 54, and the counting result is displayed every moment on the set level display 43, so that the recording mute time can be known.

Further, the output terminal 2 is connected to the recording amplifier of the tape recorder, and the 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 with just one touch by pressing the automatic setting switch 7, so compared to the conventional recording level setting,
It is extremely easy to operate.

The reason why automatic recording level setting by one-touch operation has been made possible is based on experimental results showing that the maximum value measurement time determined by the time setting circuit 6 is about 10 seconds for most input signals. .

FIG. 2 is a diagram showing the experimental results of plotting the relationship between the maximum value measurement time and the measured maximum level for three types of input sources. Source is A
In the case of (speech), the maximum level is saturated at the fourth second. 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 10 seconds or more, except for special sources.

On the other hand, from the viewpoint of the operator's usability, it seems better to shorten this measurement time, so it is approximately 5 to 5 minutes.
It is desirable to set the time width of the time setting circuit 6 to about 10 seconds.

FIG. 3 shows a more specific embodiment of the main part 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 simply pressing the automatic setting switch 7. When automatic setting switch 7 is shorted, 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
added to gate circuits 12 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, the period 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 "H" and the other output - is set to "L". do. Therefore, OR gate circuit 3
4, one input of AND gate circuits 12 and 13 is set to "H", and the pulse from AD converter 11 passes through AND gate circuit 12, passes through OR gate circuit 37, and enters the counting input terminal (IN) of digital counter 8. At the same time, the clear pulse from the pulse generator 10 is also applied to the AND gate circuit 13.
It is applied to the clear input terminal (CL) of the digital counter 8 through the CL signal.

The digital counter 8, latch circuit 14, and comparator 15 constitute the maximum value holding circuit 5 shown in FIG. , and has the function of holding. That is, the maximum value holding operation is performed digitally, and the digital output thereof 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 input during the maximum value measurement period during which the monostable multivibrator 32 is generating pulses. That is, when the maximum input 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, in special cases such as when inputting low-level classical music), instead of pressing and immediately releasing the automatic setting switch 7, the operator can adjust the measurement period according to his/her wishes. Just hold it down for as long as you want. When automatic setting switch 7 is held down, inverter 3
The output of 3 is "H", and even if the pulse generation operation of the monostable multivibrator 32 stops and the Q output becomes "L", "H" is applied to one input of the OR gate circuit 34. "H" is applied to one input of AND gate circuits 12 and 13, and AD converter 11 and pulse generator 10
The pulses from the digital counter 8 continue to be sent to the digital counter 8. When automatic setting switch 7 is released, inverter 3
The output of 3 becomes "L", the input to the digital counter 8 is cut off by 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 input 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 is
A clock pulse for the AD converter 11 and a clear pulse for clearing the digital counter 8 every time the AD converter 11 samples are generated. This clear pulse is synchronized with the AD converter 11 sampling every fixed period, and
It is generated immediately before the converter 11 converts the sample value into a pulse number and outputs it. In short, the clear pulse applied to the clear input terminal (CL) of the digital counter 8 clears the count value of the digital counter 8 to 0 so as not to accumulate the previous count value, and returns the count value corresponding to the next sample value. Prepare. 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, the latch circuit 14, and the comparator 15 form the maximum value holding circuit 5 in FIG. It functions to maintain the previous value. The comparator 15 compares the count outputs A ₁ , A ₂ , A ₃ , A ₄ of the digital counter 8 with the outputs B ₁ , B ₂ , B ₃ , B ₄ of the latch circuit, and determines that A>B
A pulse is output only when such a relationship exists, and this pulse unlatches the latch circuit 14 and outputs it to the non-latch circuit 14.

As is clear from the above explanation, latch circuit 1
4 and a comparator 15 update the latch output only when the count outputs A ₁ , A ₂ , A ₃ , A ₄ of the digital counter 8 are respectively larger than the previous latch outputs B ₁ , B ₂ , B ₃ , B ₄ , When it is small, the previous output is retained.
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 resistive attenuator and an analog switch. Resistors 16, 17, analog switch 18, and buffer amplifier 19 constitute a first stage resistance attenuator, and analog switch 18 is conductive when output _B1 of latch circuit 14 applied to its gate is "H". Since it is in a cutoff state when the output is "L", the output of the latch circuit 14 ends up being
When B ₁ is “H”, the first stage resistor attenuator is resistor 1
It exhibits a damped state with a partial pressure ratio of 6 and 17, and becomes a non-damped state when B ₁ is "L". The buffer amplifier 19 serves to prevent mutual influence between the first and second stage resistor attenuators. Similarly, resistors 20, 21, analog switch 22, and buffer amplifier 23 form a second stage resistance attenuator, resistors 24, 25, analog switch 26, and buffer amplifier 27 form a third stage resistance attenuator, and resistor 28, 29, analog switch 30 and buffer amplifier 31 are 4
Each stage constitutes a resistance attenuator. Each of the resistive attenuators from the first stage to the fourth stage is connected in series to form a gain control circuit 3, and each resistive attenuator has a different attenuator in the attenuation state, for example, 1 dB, 2 dB, 3 dB, 4 dB. , 8dB.

When the measurement period ends, the AND gate circuit 12
and 13 are in the blocking state, but each time the operator presses the manual setting switch 40 in this state, one counting pulse is generated by the counting pulse generator 39, and one counting pulse is generated by the AND gate. Applied to one input of circuit 38. The output of the AND gate circuit 35 is connected to the other input of the AND gate circuit 38, and "H" is applied thereto. That is, after the automatic setting is completed, the output of the monostable multivibrator 32 is "H", and since the automatic setting switch 7 is also not pressed, both inputs of the AND gate circuit 35 are "H". Therefore, the counting pulse from the counting pulse generator 39 is applied to the AND gate circuit 38, passed through the OR gate circuit 37, and applied to the counting input 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, the manual setting switch 40 is provided with a count UP direction and a count DOWN direction, respectively, and the UP input of the digital counter,
If configured to be added to the DOWN input, the set level can be moved in either direction up or down from the automatically set level.

Furthermore, a display is provided that can distinguish between the measurement period and the period after the automatic setting ends (manual setting available period). 36
has two-color light emitting diodes that make up the display device,
For example, when current flows through D ₁₆ , it emits red light, and when current flows through D ₁₇ , it emits green light.

As already explained, the output of the OR gate circuit 34 is "H" during the measurement period, and the output of the AND gate circuit 35 is "H" after the automatic setting is completed. Therefore, from these outputs the resistors r ₇ and
If you connect the light emitting diodes D ₁₆ and D ₁₇ so that current flows through r ₈ , the red color will change during the measurement period.
Then, when the automatic setting is completed and manual setting becomes possible, a green light is emitted, and it is very convenient to place this on the panel surface of the tape deck. In addition,
This display is not limited to two-color light-emitting diodes; it can also be easily distinguished by lighting the light-emitting diode only when in one of the modes, or by having it blink during the measurement period and turn it on continuously after the settings are complete. Can be implemented. Further, to explain the display drive circuit, so-called decoder 41 and setting level (attenuation amount) display 43, the decoder 41 operates the latch circuit 14 in order to display the attenuation amount setting value of the gain control circuit 3 on the attenuation amount display 43. A BCD to decimal decoder 42 and a minimum resistance attenuator (for example 1 dB) analog switch 1 connected to the outputs B ₂ , B ₃ , B ₄
It is constituted by a switching circuit 44 connected to the same output _B1 to 8. Output of latch circuit 14
When _B1 is at "H", the switching element _Q1 is turned on and the switching element _Q2 is turned off by the inverter _Q3 . Conversely, when the output B ₁ of the latch circuit 14 is "L", the switching element Q ₁
is in the cutoff state and Q ₂ is in the conduction state. When switching element _Q1 is in conduction state ( _Q2 is in cutoff state),
The conditions for lighting the light emitting diodes D ₁ , D ₃ , D ₅ ...D ₁₅ of the attenuation amount display 43 from the power supply V _CC through the resistor r ₁ are satisfied, and in the opposite case, the conditions for lighting the light emitting diodes D ₁ , D ₃ , D ₄ ...D ₁₄ of the attenuation amount display 43 are satisfied. The lighting conditions are met.

The other outputs B ₂ , B ₃ ,
A BCD to decimal decoder, that is, a 2-way to 10-way decoder 42 connected to B ₄ detects the light emitting diodes D ₁ , D ₃ , ...D ₁₅ (or D ₀ , D ₂ , ...D _{14 )} under the above-mentioned lighting conditions. ) satisfies one lighting condition out of eight. In other words, the output B ₁ of the latch circuit 14 and
The combination of the lighting conditions of B ₂ , B ₃ , and B ₄ causes 1 out of 16 light emitting diodes to be lit. That is, read the attenuation amount of the gain control circuit 3, and set each resistor attenuator to 1 dB, 2 dB, 4 dB, for example.
dB, 8dB, 16 light emitting diodes D ₀ ,
_D1 ,... _D15 can display 0dB to 15dB.

Further, the configuration of the apparatus of this embodiment will be explained using FIG. 4. The configuration of FIG. 4 is obtained by adding a muting time display function to the automatic level setting circuit having the attenuation amount display function of the gain control circuit of FIG. 3. In FIG. 4, 45 is a recording mute switch, and this switch 45 puts the recording amplifier 52 connected to the output terminal 2 into a no-input state, and the switch 45 can be operated from the contact a side to the b side. This cuts off the recording signal supplied to the recording head 53, creating a so-called muting state in which no signal is recorded on the magnetic tape.

Display changeover switches 46, 47, 48, 49 and a counting pulse generation switch 50 are provided in conjunction with the recording/mutating switch 45.
The switches 46 to 49 are on the attenuation amount display side (contact a
The counting pulse generator 51 is driven from the time display side (contact b side) to the time display side (contact b side). The number of output pulses from this counting pulse generator 51 is calculated by a digital counter 54.
This counting output is supplied to the decoder 41 via the contacts b side of the aforementioned changeover switches 46, 47, 48, and 49. The output of this decoder 41 is the light emitting diode D ₀ , D ₁ ,
The set level display 43 consisting of D ₂ , . . . D ₁₅ is driven to display the count of the counter 54. If the counting pulse generator 51 outputs one pulse per unit time, the display 43 will display the following per unit time:
The position of the lit light emitting diode moves as D _o →D _o+1 (where n=0 to 14), and by moving the lit position, a recording mute time table can be performed. That is, the setting level display 43 normally displays the amount of attenuation, and displays the recording mute time during recording mute.

Fig. 5 shows the external appearance of a tape recorder incorporating the circuits shown in Figs. 3 and 4, in which 55 is a cassette mounting section, 56 is a group of tape running operation buttons, and 57 is a digital level that displays the recording and playback level. It is a meter. As shown in the figure, the attenuation amount display 43 has light emitting diodes D ₀ to _{D 15} arranged tilting upward to the right from the lowest level to the highest level, and the manual setting switch 40 has an UP switch 40a and a DOWN switch.
The switch 40b is provided separately. Furthermore, a display 36 consisting 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, according to the tape recorder of the present invention, since the recording level can be set with a single touch operation, the operation is extremely simple compared to the conventional level setting, and the recording level can be adjusted according to the maximum value of the input signal level. Because the level setting is realized,
Not only can you set high-quality recording conditions that do not cause saturation distortion, but the setting level is also displayed, allowing the user to monitor the automatic level setting operation from the outside, allowing you to record with confidence. .

Furthermore, when recording and muting, the recording mute time is displayed on the display that displays the above-mentioned setting level, so the recording mute time can be made uniform at low cost, and in this way, no-signal sections are formed between songs. Automatic cueing operation can be performed reliably when playing back a tape.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, and FIG.
The figure shows experimental results for explaining the embodiment of the present invention, Figures 3 and 4 are circuit diagrams of a specific embodiment of the present invention, and Figure 5 shows the external appearance of the embodiment of the present invention. FIG. 1...Input terminal, 2...Output terminal, 3...Gain control circuit, 4...Level detector, 5...Maximum value holding circuit, 6...Time setting circuit, 7...Automatic setting switch, 8...Digital Counter, 9... Peak detector, 10... Pulse generator, 11... AD converter, 12, 13... AND gate circuit, 14...
...Latch circuit, 15...Comparator, 32...
Monostable multivibrator, 34, 37...OR
Gate circuit, 35, 38...AND gate circuit,
36...Two-color light emitting diode, 39...Counting pulse generator, 40...Manual setting switch, 41...
511... counting pulse generator, 54... digital counter.

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 level detector for detecting the signal level of the recording signal transmission path; 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. , a recording mute switch for muting the recording signal, a clock pulse generator that operates in connection with the operation of the recording mute switch, a counter that counts the output pulses of the clock pulse generator, and a counter that counts the output pulses of the clock pulse generator; A changeover switch that selects the output of the value holding circuit and the output of the above-mentioned counter, a display drive circuit that operates in response to the output applied through this changeover switch, and a setting level connected to the output terminal of this display drive circuit. The gain control circuit is equipped with a display, and when the automatic setting switch is operated, the gain control circuit is automatically controlled according to the maximum input level to the recording signal transmission path during the time set by the time setting circuit, and the gain control circuit is automatically controlled according to the maximum input level to the recording signal transmission path during the time set by the time setting circuit. Display the setting amount of the gain control circuit on the setting level display with the output of the value holding circuit,
A tape recorder characterized in that the mute time is displayed on the setting level display when the recording mute switch is operated.