JPS6325767Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is designed to play a stereo signal when the headphone plug is inserted into the jack, and to play a monaural signal from the speaker when the headphone plug is removed from the jack. The variable resistor connected between the preamplifier circuit and the main amplifier circuit of the signal and right signal playback circuits is used to adjust the volume of the left and right signal playback circuits when playing stereo signals, but when playing monaural signals, The present invention relates to a signal amplification circuit in which, when reproducing a signal, a variable resistor of one reproducing circuit is used for volume adjustment, and a variable resistor of the other reproducing circuit is used for adjusting sound quality.

The present invention will be explained below according to the drawings. 1a,
1b is a reproduction circuit that reproduces the left signal and the right signal;
The magnetic heads 2a, 2b, respectively, the magnetic heads 2a,
A preamplifier circuit 3 that amplifies the signal reproduced by 2b
a, 3b, variable resistors 4a, 4b connected to the output sides of the preamplifier circuits 3a, 3b, and main amplification circuits 5a, 5b. Reference numeral 6 designates a jack switch. When a headphone plug (not shown) is inserted into the jack (not shown), contact pieces 8a, 8b and contact pieces 9a, 9b are turned off. A voice conversion section is connected to the output side of the main amplifier circuits 5a and 5b. 10 is a speaker selectively connected via contact pieces 9a and 9b, 11 is a transistor for switching between monaural and stereo, and the emitter-collector is connected between the output sides of the left signal and right signal preamplifier circuits 3a and 3b. The base is connected to the contact piece 8a of the jack switch 6,
Grounded via 8b. 12 is a capacitor for high frequency cut whose one end is connected to the variable resistor 4a, and the other end is connected to the contacts 8a and 8 of the jack switch 6.
Grounded through b.

Next, the operation of the signal reproducing circuit of the present invention will be explained. First, we will explain the case where a headphone plug is inserted into a jack and stereo playback is performed. The information recorded on the tape 13 is reproduced by the magnetic heads 2a, 2b, and the information recorded on the tape 13 is reproduced by the preamplifier circuits 3a, 2b.
3b and is amplified. At this time, the contacts 8a and 8b of the jack switch 6 are turned off, so
Transistor 11 is turned off and capacitor 12
One end is open. Therefore, the signals amplified by the preamplifier circuits 3a and 3b are respectively applied to the main amplification circuits 5a and 5b, where they are amplified and then applied to the headphone via the contacts 7a and 7b of the jack switch 6, where they are reproduced in stereo. . At this time, by adjusting the resistance values of the variable resistors 4a and 4b, the magnitude of each signal changes, and the volume is adjusted.

Next, a case will be described in which the headphone plug is pulled out from the jack and monaural reproduction is performed through the speaker 10. As described above, the signals reproduced by the magnetic heads 2a and 2b enter the preamplifier circuits 3a and 3b, respectively, and are amplified. However, since the contacts 8a and 8b of the jack switch 6 are turned on at this time, the transistor 11 is turned on.
Therefore, the right signal amplified by the preamplifier circuit 3a passes through the emitter-collector of the transistor 11, is mixed with the left signal amplified by the preamplifier circuit 3b, and is applied to the main amplifier circuit 5b, whose output is sent to the jack switch. Speaker 10 via contact pieces 9a, 9b of 6
and drives the speaker 10. By the way, when using the speaker 10 with a narrow band, it is desirable to cut out high frequencies. Therefore, in the present invention, the variable resistor 4a, which does not require volume adjustment during monaural reproduction, is used as a variable resistor for cutting high frequencies. That is, the variable resistor 4
Condenser 12 for high frequency cut connected to a
Since the other end is grounded via the jack switch 6, it is activated, and the high frequency range of the signal amplified by the preamplifier circuit 3a is grounded via the capacitor 12. Since the amount of grounding can be changed by adjusting the resistance value of the variable resistor 4a, the variable resistor 4a also works for adjusting sound quality.

It goes without saying that the volume can be adjusted by changing the resistance value of the variable resistor 4b at this time.

As mentioned above, in the signal reproducing circuit of the present invention, a variable resistor is connected to the output side of each preamplifier circuit, and one of the variable resistors is connected to a monaural/stereo switching transistor and is activated or deactivated by a jack switch. Since the capacitor that is activated is connected, the variable resistor is used to adjust the volume of the left and right signals during stereo playback.
During monaural reproduction, one variable resistor is used for adjusting the volume, and the other variable resistor is used for adjusting the sound quality when using a speaker with a narrow band, which is convenient in practice.

[Brief explanation of the drawing]

The figure is a signal reproducing circuit diagram of the present invention. 1a, 1b... Regeneration circuit, 3a, 3b... Preamplifier circuit, 4a, 4b... Variable resistor, 5a, 5
b...Main amplifier circuit, 6...Jack switch, 1
0...Speaker, 11...Transistor, 12...
…condenser.

Claims (1)

[Scope of utility model registration request] A regeneration circuit for left and right signals each having a preamplifier circuit, a variable resistor connected to the output side of the preamplification circuit, and a main amplification circuit, and a jack switch connected to the output side of the regeneration circuit. , a speaker selectively connected to the one reproducing circuit by the jack switch, and an output signal of the preamplifier circuit of the one reproducing circuit controlled by the jack switch to the preamplifier circuit of the other reproducing circuit. It consists of a transistor to be mixed with the output signal and a capacitor for high frequency cut, one end of which is connected to the variable resistor and the other end is grounded via the jack switch.When the headphone plug is inserted into the jack, the variable resistor is It is used to adjust the volume of the left and right signals, and when the headphone plug is not inserted into the jack, the variable resistor of one reproduction circuit is used as a variable resistor to adjust the volume of the output signal mixed by the transistor, and the other A signal reproducing circuit characterized in that a variable resistor of the reproducing circuit is used for adjusting sound quality.