JPS6258167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic recording level correction device suitable for use in tape decks, etc. In particular, when a signal exceeding an appropriate recording level (hereinafter referred to as a distortion level signal) is input, this invention corrects the distortion level signal. The purpose is to automatically correct the recording level according to the magnitude of the level signal and the frequency of input, and to perform recording with less distortion without compressing the dynamic range of the input signal.

Conventionally, recording level correction devices for tape decks and other devices have used a limiter method that attenuates only the signal that exceeds the appropriate recording level and records at a signal level that is within the appropriate recording level, and a limiter method that attenuates only the signal that exceeds the appropriate recording level, and a limiter method that attenuates only the signal that exceeds the appropriate recording level. An automatic recording level correction method has been proposed in which the attenuation amount of an attenuator is adjusted according to the signal, and the signal is recorded within the appropriate recording level. but,
In the former case, the recorded signal would be relatively flat, with the disadvantage that the dynamic range would be compressed. In the latter case, even though the dynamic range was not compressed, the amount of attenuation changed each time a signal exceeding the appropriate level was input, making it impossible to record faithfully to the input signal. Actual tape deck users record while monitoring the VU meter and peak meter, and do not change the recording level during normal recording. If this was input frequently, the recording level was gradually lowered to produce a recording with less distortion.
However, the method of manually correcting the recording level requires intuition based on experience and has the disadvantage that the operation is cumbersome.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide an automatic recording level correction device that has high input signal fidelity and reduces distortion. I will explain based on this.

FIG. 1 is a block diagram showing an embodiment of the present invention, and 1 and 2 are signal input terminals and output terminals, respectively. A gain control circuit 3 changes the gain between the input terminal 1 and the output terminal 2, and is composed of a group of resistive attenuators including an analog switch. A first counting circuit 4 counts the number of input pulses and controls the gain control circuit 3 according to the counted value. 5 is the gain control circuit 3
This is a distortion level detector that detects whether a signal passed through the 1500 exceeds an appropriate recording level. 6 is a level correction control circuit that stores the output signal of the distortion level detection section 5 and outputs a pulse according to the stored signal; It is made up of. The output pulse of the level correction control circuit 6 is input to the first counting circuit 4.
Now, in the above configuration, suppose that an audio signal is input to input terminal 1, a recording amplifier is connected to output terminal 2, and a recording current is supplied to the magnetic head. An audio signal controlled by the gain control circuit 3 is input to the distortion level detector 5 . Distortion level detector 5
The input audio signal is converted by the level detector 51 into a DC voltage according to the peak level of the signal. This DC voltage is compared with the output voltage of the reference voltage generator 52 corresponding to the distortion level by a comparator 53, and if the signal input to the distortion level detector 5 exceeds the appropriate recording level, it exceeds the appropriate recording level. A signal corresponding to the amount of distortion is obtained as an output signal of the distortion level detector 5. The output signal of the distortion level detector 5 is sent to the AD converter 6 of the level correction control circuit 6.
1 and converted to the number of pulses. The output pulse of the AD converter 61 is sent to the second count circuit 62.
are input and counted. Second count circuit 62
has the function of generating one pulse when the count value reaches a predetermined value. The output pulse of the second count circuit 62, which is the output signal of the level control correction circuit 6, is input to the first count circuit 4, which increases the attenuation amount of the gain control circuit 3 and works to suppress distortion of the recording signal. However, even if an audio signal exceeding the appropriate recording level is input, if the signal within the appropriate recording level continues, the time setting circuit 63 is connected to the second count circuit 62, and the counted value is output at regular intervals. becomes zero, so the level correction control circuit 6 does not output a pulse signal, so the recording level does not change.

That is, when the signal that has passed through the gain control circuit 3 greatly exceeds the appropriate recording level, or frequently exceeds the appropriate recording level, the level correction control circuit 6 supplies pulses to the first count circuit 4. , the signal passing through the gain control circuit 3 is attenuated to correct the recording level. Furthermore, even if a signal exceeding the appropriate recording level is input to the distortion level detector 5, converted to a pulse number by the AD converter 61, and counted by the second counting circuit 62, it is then set by the time setting circuit 63. If the signal remains within the appropriate recording level for a certain period of time, the count value of the second count circuit 62 becomes zero, so the gain control circuit 3
The amount of attenuation does not change.

FIG. 2 shows a more specific embodiment of the main part of the present invention, and the same components as in FIG. 1 are given the same reference numerals. Here, a concrete example of FIG. 1 will be explained. In FIG. 2, the gain control circuit 3 includes analog switches SW1 to SW1.
4, including a plurality of resistive attenuators R1 to R8. Each resistance attenuator R1 to R8 is controlled according to the digital output given from the first count circuit 4, and the total attenuation amount of the gain control circuit 3 is determined. The analog signal corresponding to the amount exceeding the appropriate recording level, which is the output signal of the distortion level detector 5 explained in FIG. 1, is converted by the pulse width converter 64 into a signal with a pulse width corresponding to the analog amount. Ru. Output signal of pulse width converter 64 and pulse generator 65
The output signal is input to an AND gate circuit 66, and the output terminal of the AND gate circuit 66 outputs a digital signal with a number of pulses corresponding to the amount exceeding the appropriate recording level. That is, the pulse width converter 64, pulse generator 65, and AND gate circuit 66 correspond to the AD converter 61 in FIG. The output signal of the AND gate circuit 66 is input to the second counting circuit 62 and counted. Here, assuming that the second count circuit 62 is a 4-bit binary counter and includes an output terminal that outputs a carry signal and an input terminal that sets the count value to zero, the second count circuit 62 When 16 pulses are input to , the carry signal from the second count circuit 62 is input to the first count circuit 4 and functions to control the attenuation amount of the gain control circuit 3 . Also,
The output pulse signal of the pulse generator 65 is counted by a third counting circuit 67, and is configured to generate one pulse when the counted value reaches a predetermined value. That is, by counting the output pulses of the pulse generator 65, the third counting circuit 67
It has the function of generating one pulse at regular intervals and setting the count value of the second counting circuit 62 to zero. The pulse generator 65 and the third count circuit 67 correspond to the time setting circuit 63 in FIG. As described above, it goes without saying that the embodiment shown in FIG. 2 also provides the same effects as those obtained in the embodiment shown in FIG.

As is clear from the above explanation, according to the automatic recording level correction device in the above embodiment, the dynamic range is not compressed as in the limiter method, but is attenuated every time a signal exceeding the appropriate recording level is input. Since the amount does not change, the fidelity of the input signal is not compromised. Also, when the user manually corrects the recording level, recording is only possible when a signal that exceeds the appropriate recording level is input to a particularly large extent, or when a signal that frequently exceeds the appropriate recording level is input. The level will be lowered automatically, so when recording
There is no need for complicated operations such as monitoring VU meters and gradually lowering the recording level. Further, the automatic recording level correction device in the above embodiment is applied to a recorder equipped with an automatic recording level setting device configured to set a recording level in accordance with the maximum value of a signal input during a predetermined measurement period. With this option, even if a signal that exceeds the signal input during the measurement period is input after the measurement period, the recording level can be corrected without compromising the fidelity of the input signal, making it easy for recorder users to You can easily enjoy recording without any troublesome operations such as setting and correcting the recording level.

As explained above, according to the automatic recording level correction device according to the present invention, it is possible to perform recording faithful to the input signal without compressing the dynamic range and correct the recording level so as to reduce distortion. is possible. Therefore, when used in tape decks, etc., it exhibits extremely useful effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram thereof, and FIG. 2 is a block diagram of a circuit that makes the embodiment shown in FIG. 1 more specific. DESCRIPTION OF SYMBOLS 1...Input terminal, 2...Output terminal, 3...Gain control circuit, 4...First count circuit, 5...Distortion level detector, 6...Level correction control circuit, 51...
... Level detector, 52 ... Reference voltage generator, 53
... Comparator, 61 ... AD converter, 62 ...
Second count circuit, 63...Time setting circuit, 64
... Pulse width converter, 65 ... Pulse generator, 6
6...AND gate circuit, 67...Third count circuit, R1-R8...Resistor, SW1-SW4...
...Analog switch.

Claims (1)

[Claims] 1. A gain control circuit arranged in a signal transmission path, a distortion level detector that detects a signal higher than an appropriate recording level from a signal that has passed through the gain control circuit, and an output signal of the distortion level detector. a level correction control circuit that converts and counts the digital signal into a digital signal and outputs a pulse according to the counted value when the counted value exceeds a predetermined value within a predetermined time; and an output pulse of the level correction control circuit. and a first counting circuit that counts and controls the gain control circuit according to the counted value,
The level correction control circuit includes an analog-digital converter that converts the output signal of the distortion level detector into a number of digital pulses at regular intervals, and a second converter that counts the output signal of the analog-digital converter.
1. An automatic recording level correction device comprising: a count circuit; and a time setting circuit for setting the count value of the second count circuit to zero at predetermined intervals. 2. The distortion level detector includes a level detector that detects a signal level, a reference voltage generator that generates a voltage corresponding to the distortion level, and an output signal of the level detector and an output signal of the reference voltage generator. 2. The automatic recording level correction device according to claim 1, further comprising a comparator for calculating a difference.