JPH018032Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a tuner/tape recorder switching circuit in which the amplification function of a noise reduction integrated circuit can also be used to amplify signals from a tuner.

(b) Prior Art In a tape recorder with a radio, a noise reduction circuit is used to remove high frequency component noise generated from the tape recorder. Conventionally, an audio signal from a tape recorder is input to this noise reduction circuit, and even when no noise reduction effect is performed, it is amplified to some extent and then added to the main amplification circuit at the subsequent stage. However, since the audio signal obtained from the tuner is directly applied to the main amplifier circuit, the audio signal applied to the main amplifier circuit is small.
Therefore, the gain of the main amplifier circuit had to be increased. Furthermore, since the audio signals obtained from the tuner and the tape recorder are applied to the amplifier circuit at different locations, the length of the printed wiring pattern becomes longer.

(c) Purpose of the invention The present invention eliminates the above-mentioned drawbacks by adding the audio signal from the tuner to the noise reduction circuit in the same way as the audio signal from the tape recorder.
In addition to increasing the audio signal applied to the main amplifier circuit and eliminating the need to increase the gain of the main amplifier circuit, when the audio signal from the tuner is applied to the noise reduction circuit, the noise reduction effect is activated by turning the noise switch on and off. The aim is to ensure that employees do not have to work regardless of their circumstances.

(d) Structure of the invention The present invention adds an audio signal from a tuner and a tape recorder to a noise reduction circuit having an amplification function via a first changeover switch, and
Relating to a tuner/tape recorder switching circuit that prevents the noise reduction circuit from acting to reduce noise regardless of whether the noise switch is on or off when an audio signal from the tuner is applied to the noise reduction circuit by a second changeover switch linked to the changeover switch. .

(E) Embodiment The operation of the tuner/tape recorder switching circuit of the present invention will be explained below with reference to the drawings. 1 converts the frequency of a broadcast signal received by the antenna 2, amplifies it, detects it, etc., and outputs an audio signal. tuner 3, a tape recorder for reproducing the signal recorded on the tape and extracting the audio signal; 4, an integrated circuit noise reduction circuit; It consists of a signal circuit 6 that amplifies the applied audio signal and reduces noise, and a high-pass filter 8 whose pass frequency band can be changed by a DC signal obtained by rectifying its own output with a diode 7. A second changeover switch 9 is linked to the first changeover switch 5, and when the first changeover switch 5 is on the tuner 1 side, a signal is sent from the high-pass filter 8 to the signal circuit 6 regardless of whether the noise switch 10 is on or off. The leading signal path 11 is always turned off. 12 is a main amplifier circuit, and 13 is a speaker.

Next, the operation of the tuner/tape recorder switching circuit of the present invention will be explained. First, in order to listen to the audio signal from the tape recorder 3, the first changeover switch 5 is switched to a tape recorder side different from that shown in the figure. Then, the audio signal reproduced by the tape recorder 3 is applied to the signal circuit 6 via the first changeover switch 5, is amplified, is supplied to the main amplification circuit 12, is further amplified, and is input to the speaker 13. to drive. By the way, in order to remove high frequency component noise, the high frequency components of an audio signal are sometimes emphasized and recorded on tape. The audio signal is reproduced by the tape recorder 3 and transmitted to the signal circuit 6.
When the audio signal is added to the audio signal, it is necessary to reduce the emphasized high frequency components and restore the original audio signal. A noise reduction circuit 4 performs this, extracting high frequency components contained in the audio signal using a high-pass filter 8, and transmitting the output to the signal circuit 6 via a second changeover switch 9, which is in a state different from that shown in the figure. In addition, the emphasized high frequency components of the audio signal applied to the signal circuit 6 are canceled to restore the original audio signal. The high-pass filter 8 rectifies the output of the high-pass filter 8 so that the larger the applied DC signal, the more signals are passed. Accordingly, the high frequency component is attenuated by the signal circuit 6. Therefore, the speaker 13 emits high-quality sound in which high-frequency component noise is canceled.

When the tape recorder 3 plays back the audio signal recorded on the tape without emphasizing the high-frequency components, if the signal circuit 6 attenuates the high-frequency components as described above, the original sound will be damaged.
At this time, the noise switch 10 is placed in a different state from that shown in the figure, and the signal from the high-pass filter 8 is grounded via the noise switch 10 so that it is not applied to the signal circuit 6.

Next, when listening to the audio signal from the tuner 1, the first changeover switch 5 is switched to the state shown in the figure. Then, the audio signal from the tuner 1 is amplified by the signal circuit 6, enters the main amplification circuit 12, is further amplified and applied to the speaker 13, and drives the speaker 13. By applying the audio signal from the tuner 1 to the signal circuit 6 in this way,
Since the signal circuit 6 can obtain a gain of 13 dB, even if the overall gain is required to be 40 dB, the gain of the main amplifier circuit 12 only needs to be 27 dB. As a result, the amount of negative feedback of the main amplifier circuit 12 can be increased, so that noise and distortion generated inside the main amplifier and appearing in the output can be reduced. By the way, when the first changeover switch 5 is switched so that the audio signal from the tuner 1 is applied to the noise reduction circuit 4, if the noise reduction effect is activated, the high frequency components of the audio signal will be attenuated and the original sound will be damaged. , it is necessary to prevent the noise reduction effect from working. Therefore, when the first changeover switch 5 is set to the tuner side as shown, the second changeover switch 9 is turned off as shown, and the noise switch 10 is turned off.
Even if the high-pass filter 8 is in the on state as shown in the figure, the signal path 11 applied to the signal circuit 6 from the high-pass filter 8 is always turned off.

(F) Effects of the invention As mentioned above, the tuner/tape recorder switching circuit of the present invention amplifies the audio signal obtained from the tuner in addition to the noise reduction circuit.
There is no need to increase the gain of the main amplifier circuit too much. Therefore, the amount of negative feedback of the main amplifier circuit can be increased, and a high quality audio signal can be obtained from the main amplifier circuit. Moreover, when the first changeover switch is switched to the tuner side,
The noise reduction circuit in the second changeover switch has no relation to whether the noise switch is on or off, so it does not have a noise reduction effect, so when the first changeover switch is switched to the tuner side, the noise switch is turned on. Even if an audio signal is applied to the noise reduction circuit without realizing that it is present, the disadvantage that the original sound is damaged is eliminated.

[Brief explanation of the drawing]

The figure is a tuner/tape recorder switching circuit diagram of the present invention. 1... Chuyuna, 3... Tape recorder, 4...
...Noise reduction circuit, 5...First changeover switch, 6
...Signal circuit, 9...Second changeover switch, 10...
...Noise switch.

Claims (1)

[Scope of utility model registration request] Frequency conversion of broadcast signals received by the antenna,
A tuner that amplifies and detects and outputs audio signals,
a tape recorder for reproducing signals recorded on tape and extracting audio signals; a signal circuit connected to the tuner or tape recorder by a first switch to amplify the audio signal and reduce noise; and its own output. a noise reduction circuit having a high-pass filter whose pass frequency band can be changed by a DC signal obtained by rectifying the signal with a diode, and a noise reduction circuit that is switched in conjunction with a first changeover switch, and the first changeover switch is switched to the tape recorder side. and a main amplifier circuit connected to the noise reduction circuit.