JP2670176B2 - Automatic recording level setting circuit for audio equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic recording level setting circuit for audio equipment.

2. Description of the Related Art Conventionally, for example, in a tape recorder equipped with a compact disc (hereinafter referred to as "CD") player, the recording signal input from the CD player at the time of recording a CD is temporarily adjusted by the recording level setting volume, and then the recording circuit is adjusted. By supplying it, the recording signal from the CD player is recorded at an optimum level. Then, in such a tape recorder, the setting position of the recording level setting volume is adjusted according to the level of the recording signal input from the CD player so that the setting position of the recording level setting volume is in the optimum level setting state. There was an automatic recording level setting circuit that automatically controlled the position.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such an automatic recording level setting circuit of a tape recorder, in order to detect the recording level setting volume setting position, a position detection volume which is interlocked with the recording level setting volume is used. The position detecting volume is separately provided, and the setting position of the recording level setting volume is detected. Therefore, in such a conventional automatic recording level setting circuit, the number of parts required for the interlocking position detection volume is increased and the configuration is complicated, resulting in an increase in cost. Further, in such a conventional configuration, the accuracy is deteriorated due to the mutual error between the volume curve (variable resistance characteristic) of the recording level setting volume and the position detecting volume which are interlocked.

The present invention has been made in view of such a point,
An object of the present invention is to provide an automatic recording level setting circuit capable of accurately controlling the setting position of the recording level setting volume with a simple configuration according to the level of an input recording signal.

Means for Solving the Problems In order to achieve the above object, in the present invention, in the automatic recording level setting circuit of an audio device for adjusting the level of a recording signal by the recording level setting volume, the level by the recording level setting volume is set. Level detection means for detecting the peak level of the recording signal before adjustment, level setting means for setting an optimum recording level based on the detection result by the level detection means, and recording reference signal of a predetermined level to generate the above-mentioned recording. The reference signal generating means to be supplied to the level setting volume, the level of the recording reference signal from the reference signal generating means adjusted by the recording level setting volume, and the optimum recording level set by the level setting means Based on the comparison means for comparison and the comparison result by the comparison means, the recording level The recording level setting volume is adjusted so that the level of the recording reference signal from the reference signal generating means whose level is adjusted by the volume setting volume matches or approximates to the optimum recording level set by the level setting means. A control means is provided.

Operation In the above configuration, the peak level of the recording signal before the level adjustment is detected by the level detecting means, and the optimum recording level is set by the level establishing means based on the detection result. The level setting means sets the optimum recording level high when the detected level is low, and sets the optimum recording level low when the detected level is high, for example.
On the other hand, the reference signal generating means generates a recording reference signal of a predetermined level, and the recording reference signal is subjected to level adjustment by the recording level setting volume. The recording reference signal after level adjustment is compared with the set optimal recording level,
The comparison result is used by the control means for adjusting the recording level setting volume. That is, the control means adjusts the recording level setting volume so that the level of the recording reference signal matches or approximates to the optimum recording level. With this, the recording level setting volume is properly set according to the level of the recording signal before the level adjustment, and thereafter, the recording signal level is set by the recording level setting volume thus adjusted. As a result, the recording signal has an appropriate level. In the above configuration, it is not necessary to detect the position where the recording level setting volume is set in order to set the recording signal to an appropriate level.

Embodiment A tape recorder equipped with a CD player will be described below with reference to the drawings as an embodiment of the present invention.

In Fig. 1, (1) is the signal input terminal on the tape recorder side where the recording signal of the right channel is input from the CD player when recording the CD to record the recording signal from the CD player to the tape recorder, and (2) is the time when recording the CD. Signal input terminal (1)
Recording level setting potentiometer for adjusting the level of the recording signal from (in this case, a rotary electric potentiometer rotated by a motor), (3) is a level setting for controlling the setting position of the recording level setting potentiometer (2) A switch circuit that is sometimes set to the contact A side by receiving the operating voltage and switches from the contact A side to the contact B side during recording. (4) receives the operating voltage at the time of level setting and becomes the operating state A reference signal generation circuit that outputs a recording reference signal of a higher frequency than that, (5) is a recording reference signal from the reference signal generation circuit (4) to the recording circuit side (amplification circuit for recording or a level display circuit described later). A low-pass filter that prevents it from being supplied and passes only the recording signal. (6) Amplifies the recording signal from the low-pass filter (5) and then outputs it to the recording head side. A recording amplification circuit (7) is a level display circuit for detecting the level of the recording signal and displaying the level. The level display circuit (7) outputs the output terminal (7a) as the recording signal becomes larger. ) ~ (7g) outputs H level sequentially from the left side and displays light emitting diode (8a)
~ (8g) is designed to be sequentially driven from the left side. (9) is a peak hold circuit that receives an operating voltage at the time of setting a level, enters an operating state, and holds a reference voltage to be supplied to a window comparator described later.
The peak hold circuit (9) has a recording signal level of +3 dB.
When the H level is output from the output terminal (7f) of the level display circuit (7), the silicon controlled rectifying element (hereinafter referred to as "SCR") (10) turns on and the voltage dividing resistors (11) and (12) Holds the determined reference voltage, and when the recording signal level is +6 dB and the H level is output from the output terminals (7f) (7g), the SCR (10) (13) turns on and the voltage dividing resistor (11)
(12) Holds the reference voltage determined by (14). Further, (15) is a reference signal generation circuit (4) supplied through the recording level setting volume (2).
The high-pass filter that passes only the recording reference signal from, the amplification circuit that amplifies the recording reference signal that passed through the high-pass filter (15), and (17) is the rectifying and smoothing the recording reference signal from the amplification circuit (16). The rectifying circuit (18) compares the rectified and smoothed output from the rectifier circuit (17) with the reference voltage held by the peak hold circuit (9) to detect the setting position of the recording level setting volume (2). A window comparator, the window comparator (18)
The reference voltage held by the peak hold circuit (9) is composed of the first and second comparators (19) and (20) and is output as the second reference voltage Vref via the voltage dividing resistor (21) in the window comparator (18). The second reference voltage Vref is input to the inverting input terminal of the second comparator (20), and is further input to the non-inverting input terminal of the first comparator (19) as the first reference voltage Vref ′ via the resistor (22). It has become. Therefore, as shown in FIG. 2, the window comparator (18) outputs the rectified and smoothed output from the rectifier circuit (17) to the first reference voltage Vref ′.
If it is smaller, the recording level setting volume (2)
Assuming that the level setting by is too small, an H level UP signal for raising the setting position of the recording level setting volume (2) is output from the first comparator (19), and the rectified and smoothed output is larger than the second reference voltage Vref. In this case, assuming that the level setting by the recording level setting volume (2) is too large, the H level for lowering the setting position of the recording level setting volume (2) from the second comparator (20) is set.
It is designed to output a DOWN signal. Further, when the rectified and smoothed output is between the first and second reference voltages Vref ′ and Vref (in the window), it is considered that the level setting by the recording level setting potentiometer (2) is in the optimum state. 19) The output of (20) goes to L level, that is, UP and DOWN
No signal is output. The input / output characteristic of the window comparator (18) changes according to the reference voltage held by the peak hold circuit (9), and is not held by the peak hold circuit (9) because the level of the recording signal is low, that is, the reference value. When the voltage is determined by the voltage dividing resistors (21) (22) (23) in the window comparator (18), the output region of the UP signal is widened by increasing the first and second reference voltages Vref, Vref ′. It will be. (2
4) is UP or DOWN from the window comparator (18)
A motor drive IC for driving the motor (25) for changing the set position of the recording level setting potentiometer (2) in a forward and reverse rotation upon receiving a signal, (26) is a reference signal generating circuit (4) and a switch circuit at the time of level setting. (3), peak hold circuit (9), window comparator (18), motor drive IC
A power supply control circuit that supplies an operating voltage to (24), such as a CD
When the player starts the peak search (CD peak level detection), the H level SET signal is input to the control terminal (27), so that the power supply transistor (29) is turned on via the inverter (28). , The supply of operating voltage is started.

Therefore, when setting the level on the tape recorder side with the start of the peak search in the CD player before recording the CD, the CD input to the signal input terminal (1) along with the peak search
The recording signal from the player is supplied to the level display circuit (7) by the switch circuit (3) without passing through the recording level setting volume (2), and the recording reference signal generating circuit (4).
The recording reference signal from is supplied to the window comparator (18) via the recording level setting volume (2). Then, the reference voltage is set in the peak hold circuit (9) based on the level detection in the level display circuit (7), and the reference voltage (that is, the first and second reference voltages) and the recording reference signal (that is, rectification). The smoothed output) is compared with the window comparator (18) to detect the setting position of the recording level setting volume (2) with respect to the recording signal level, and the motor drive IC is detected based on the detection result.
(24) and the motor (25) control it to a set position according to the recording signal level.

Then, at the time of CD recording after such level setting, the recording signal from the CD player input to the signal input terminal (1) is switched by the switch circuit (3) via the recording level setting volume (2) to the level display circuit ( 7), the recording signal is supplied to the recording amplification circuit 6, and the recording signal is recorded after being adjusted to an appropriate level by the recording level setting volume 2.

In this embodiment, the reference voltage is held by the peak hold circuit in two types of +3 dB and +6 dB, but by making it more than that, and by further finely detecting the level every +3 dB in the level display circuit. The setting position of the recording level setting volume may be controlled more finely. Further, in this embodiment, the SET signal is input at the start of the peak search of the CD player, but the present invention is not limited to this. Further, although only the right channel system has been described in this embodiment, the left channel system is the same, and the output from the level display circuit on the left channel side is also input to the peak hold circuit. The setting position of the level setting volume is controlled similarly.

EFFECTS OF THE INVENTION As described above, according to the automatic recording level setting circuit of the present invention, the recording level adjusting volume is set based on its own output. It is not necessary to provide a member, the circuit configuration is simple, and the cause of the error is eliminated, so that the recording signal can be accurately set to an appropriate level.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is an input / output characteristic diagram of the window comparator. (1) …… Signal input terminal, (2) …… Recording level setting potentiometer, (3) …… Switch circuit, (4) …… Reference signal generation circuit, (9) …… Peak hold circuit, (18) …… Wind comparator, (24) …… Motor drive IC.

Claims (1)

(57) [Claims] 1. An automatic recording level setting circuit of an audio device for adjusting a recording signal level by a recording level setting volume, the level detection for detecting a peak level of a recording signal before the level adjustment by the recording level setting volume. Means, a level setting means for setting an optimum recording level based on the detection result of the level detecting means, a reference signal generating means for generating a recording reference signal of a predetermined level and supplying it to the recording level setting volume, Comparing means for comparing the level of the recording reference signal from the reference signal generating means adjusted by the recording level setting volume with the optimum recording level set by the level setting means, and based on the comparison result by the comparing means The level adjusted by the recording level setting volume And a control means of the audio device for adjusting the recording level setting volume so that the level of the recording reference signal from the quasi-signal generating means matches or approximates to the optimum recording level set by the level setting means. Automatic recording level setting circuit characterized by.