JPS634303Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a tape recorder circuit, and in particular, to a stereo tape recorder configured so that an input signal from a built-in microphone can be input to a playback amplifier during tape playback, and equipped with a variable resistor for stereo balance. It is possible to attenuate the tape playback signal of either the left or right channel using the balance variable resistor, simultaneously activate the built-in microphone, and input the microphone input signal to the playback amplifier instead of the tape playback signal of the attenuated channel. It was made possible.

In recent years, tape recorders have become smaller and smaller, and it has become popular to attach the tape recorder to the belt of your pants and listen to tape playback signals through headphones while walking. Therefore, when listening to reproduced sound through the headphone, the surrounding sounds are blocked by the cover of the headphone, making it impossible to hear the surrounding external sounds while the tape recorder is playing back. Conventionally, in order to hear such ambient sounds through headphones, or to talk to the person facing you through the headphones, a talk switch was provided that was operated as needed, and the talk switch controlled the playback volume of the tape at a constant level. There was one that was configured so that at the same time attenuated by the same amount, surrounding external sounds or speech input into the built-in microphone could be heard through headphones.

However, this conventional tape recorder has a special talk switch to turn on/off the built-in microphone, so it is small and
With portable tape recorders, it is difficult to place the switch knob in terms of space and design.

The present invention has been proposed in view of these points, and an embodiment of the tape recorder circuit of the present invention shown in the drawings will be described below.

In the figure, reference numeral 1 denotes a built-in microphone whose power supply (+B) is connected to a hot side line through a resistor 2, and a switching circuit 4 is connected to the ground side line of the built-in microphone 1 and the microphone amplifier 3. 5 and 6 are playback heads for left and right channels that play back the stereo signals recorded on the tape 7, and the tape playback signals from the playback heads 5 and 6 are sent to a playback preamplifier 8 for the left channel and a playback preamplifier 9 for the right channel.
are input respectively.

10 is a variable resistor for stereo balance, one end of which is connected between the output lines of the left and right reproduction preamplifiers 8 and 9, with one end at point A and the other end at point C, and 11 is a DC cut capacitor.

The switching circuit 4 includes a first transistor 12 whose collector and emitter are connected between the ground line of the built-in microphone 1 and the ground, and a second transistor whose collector and emitter are connected between the base of the first transistor 12 and the ground. 13, a bias resistor 14 connected between the base of the first transistor 12 and the power supply (+B) line, and a bias resistor 15 connected between the base of the second transistor 13 and the power supply (+B) line. The base of the second transistor 13 is connected to the right channel side end point C of the balancing variable resistor 11 via a resistor 16. The central point B of the variable resistor 10 is connected to the ground, and the grounded movable terminal 17 is connected from the central point B to one end on the A point side.
Alternatively, by moving the other end toward point C, the balance between the left and right tape playback signals can be adjusted.

18 is a variable resistor for left channel volume, 19 is a variable resistor for right channel volume, 20 is a power amplifier for left channel, 21 is a power amplifier for right channel, and 22 is a stereo headphone terminal.

What is important here is that when the movable terminal 17 of the variable resistor 10 is moved to the other end point C, the bias resistor 14 is
15 is set in advance so that the first transistor 12 is turned on and the built-in microphone 1 and microphone amplifier 3 are put into operation.

The present invention is constructed as described above, and its operation will be explained below.

By moving the movable terminal 17 of the balancing variable resistor 10 from point B in the center as a neutral point toward point A at one end or toward point C at the other end, the balance between the left and right tape playback signals can be adjusted to the normal stereo level. It can be adjusted in the same way as a tape recorder. At this time, the built-in microphone 1 is set to be inactive.

Then, connect the movable terminal 17 to the other end C of the variable resistor 10.
When it moves to the point, the tape playback signal of the right channel is grounded via the capacitor 11, so
This reproduced signal is attenuated and is not input to the power amplifier 21. At the same time, the second transistor 13 is set in advance to be reversed from ON to OFF, so the first transistor 12 is
The built-in microphone 1 and the microphone amplifier 3 are automatically activated.

As a result, the external sound or dialogue sound input to the built-in microphone 1 is amplified by the microphone amplifier 3 and then input to the right channel power amplifier 21. As a result, the tape playback signal can be heard on the left channel of the stereo headphone. However, on the right channel, external sounds input from the built-in microphone 1 can be heard.

To cancel the external sound listening operation using the built-in microphone 1, the movable terminal 17 of the variable resistor 10 should be returned from point C at the other end to point A at one end. You can listen to it with stereo headphones while adjusting the balance of the playback signal.

As described above, the tape recorder circuit of the present invention is a stereo tape recorder that is configured so that an input signal from a built-in microphone can be input to a playback amplifier during tape playback, and is equipped with a variable resistor for stereo balance. A switching circuit to be controlled is connected, and the tape playback signal of either the left or right channel is attenuated by the stereo balance variable resistor, and at the same time, the switching circuit is operated to operate the built-in microphone, and the attenuated Since it is configured so that the microphone input signal is input to the playback amplifier instead of the tape playback signal of the channel, the operation and non-operation of the built-in microphone can be electrically switched using a variable resistor for balance. Since this can be done automatically and there is no need to prepare a special space for a mechanical switch unlike in the past, it is extremely useful for small tape recorders that use headphones. Furthermore, according to the present invention, it is possible to listen to the tape playback sound on one channel of the headphone and listen to the external sound input to the built-in microphone on the other channel, so it is possible to listen to the tape playback signal and the built-in microphone as in the past. Compared to the system where each signal is mixed with the input signal and listened to, each signal can be adjusted independently and at the same time each signal can be heard clearly.The present invention provides a practical headphone stereo tape recorder. This is something that can be provided.

[Brief explanation of the drawing]

The figure shows an embodiment of the tape recorder circuit of the present invention. 1...Built-in microphone, 4...Switching circuit,
5, 6... Playback head, 8, 9... Playback preamplifier, 10... Stereo balance variable resistor, 1
7...Movable terminal, 20, 21...Power amplifier.

Claims (1)

[Scope of utility model registration request] In a stereo tape recorder configured so that an input signal from a built-in microphone can be input to a playback amplifier during tape playback and equipped with a variable resistor for stereo balance, a switching circuit for controlling the operation of the built-in microphone is connected to the stereo balance. The tape playback signal of either the left or right channel is attenuated by a variable resistor, and at the same time the switching circuit is operated to operate the built-in microphone, and the tape playback signal of the attenuated channel is attenuated by the microphone input. A tape recorder circuit characterized by inputting a signal to a playback amplifier.