JPS6222161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tape recorder capable of performing microphone mixing during tape playback.

Conventional configuration and its problems In general, a tape recorder capable of microphone mixing has magnetic heads 1L and 1R, as shown in Figure 1.
The playback signals from the microphones are input to the power amplifiers 3L and 3R through the preamplifiers 2L and 2R, while the playback signals from the respective microphones connected to the microphone terminals 4L and 4R are amplified by the microphone amplifiers 5L and 5R to record and play. When the switches S _1-1 and S _1-2 are turned on to the playback side and the mixing switch S ₂ is on, the microphone signals from the microphone amplifiers 5L and 5R are passed through the resistors R ₁ and R ₂ to the power amplifier 3L. ,3
The configuration was such that microphone mixing was performed by inputting to R, and audio was output from speakers 6L and 6R. However, in the above-mentioned tape recorder, microphone amplifiers 5L and 5R are required for each channel to amplify the playback signal from the microphones connected to the microphone terminals 4L and 4R and input it to the recording amplifier, making the configuration extremely complicated. It had the disadvantage of becoming

OBJECT OF THE INVENTION The present invention is intended to eliminate such conventional drawbacks, and its purpose is to provide a tape recorder with a simple configuration in which a microphone terminal for recording can also be used as a mixing terminal. be.

Structure of the Invention In order to achieve the above object, the tape recorder of the present invention transmits playback signals from the left and right magnetic heads or from microphones connected to the left and right microphone terminals to the left and right sides via a recording/playback switch. The left and right microphone terminals are connected to each other with two resistors, and the midpoint between the two resistors is connected to the mixing amplifier and grounded through the resistor. The output terminal of the amplifier is grounded by a switch responsive to the upper write/re-switch, and the voltage is divided by resistors and added to the outputs of the left and right amplifiers.

DESCRIPTION OF EMBODIMENTS The present invention will be described below with reference to drawings of embodiments. FIG. 2 shows an embodiment of the present invention,
In the figure, 11L and 11R are magnetic heads, and when the recording/reproducing switches _S11-1 to _S11-4 are in the playback position, the playback signals from the magnetic heads 11L and 11R are sent to the preamplifiers 12L and 12R and the power amplifier 13.
It is amplified by L, 13R, and the speaker 14L, 14R
More audio output will be reported. Mixing switch SW ₁₂ is now in the on position, and microphone terminal 15 is
Assuming that a microphone is connected to the microphone terminal 15L, the reproduction signal from the microphone connected to the microphone terminal 15L is voltage-divided by the resistors R ₁₁ to R ₁₅ and input to the mixing amplifier 16.
The signal from 6 is input to left and right power amplifiers 13L and 13R by resistors R ₁₆ and R ₁₇ and amplified.
Audio output is reported from the speakers 14L and 14R. On the other hand, when a microphone is connected to the microphone terminal 15R, the reproduction signal from the microphone connected to the microphone terminal 15R is divided by the resistors R ₁₁ to _{R 15} and input to the mixing amplifier 16.
The signal from the mixing amplifier 16 above is a resistor
Left and right power amplifiers 13L, 1 by R ₁₆ and R ₁₇
It is input to 3R and amplified, and then sent to the speaker 14.
Audio output is reported from L and 14R. here,
It goes without saying that the resistors R ₁₆ and R ₁₇ are selected to such an extent that the crosstalk of the reproduced signals from the magnetic heads 11L and 11R is not worsened. Note that when the mixing switch SW ₁₂ is turned off, microphone mixing is not performed during playback. Next, record switch S _11-1
When ~S _11-4 is at the playback position, playback signals from the microphones connected to the microphone terminals 15L and 15R are amplified by the preamplifiers 12L and 12R and input to the recording amplifier. Also, the microphone playback signal passing through the resistors R ₁₃ and R ₁₄ is amplified by the mixing amplifier 16, but since the output end of the mixing amplifier 16 is grounded by the recording/playback switch S _11-3 , the microphone mixing signal is amplified by the mixing amplifier 16. Not done.

By the way, since the reproduced signals from the microphones connected to the microphone terminals 15L and 15R are connected through the resistors _R13 and _R14 , crosstalk during recording becomes worse. Therefore, it is necessary to select the resistor R ₁₅ to an appropriate value, and when the input impedance Z _M of the mixing microphone 16 satisfies R ₅ << Z _M , the crosstalk is expressed by the following equation.

Let Z be the microphone impedance, R ₁₁ < R ₁₃ ,
If R ₁₁ < R ₁₄ , R ₁₅ < R ₁₃ , R ₁₅ < R ₁₄ is selected, the leakage of the left microphone signal to the right microphone is V _L ′≒V _L × {R ₁₁ /Z+R ₁₁ ×R ₁₅ /R ₁₃ × R ₁₅ × R ₁₂ Z/R ₁₄ + (R ₁₂ Z)} V _L : Left microphone output V _L ′: Leakage of left microphone output to right microphone. If V _L ' is made small, the input to the mixing amplifier 16 becomes small, but there is no problem in practice as long as the amplification degree of the mixing amplifier 16 is made high. However, there is a slight leakage, so if you use it in a high-end machine, you can add a recording/playback switch S _11-4 to both ends of resistor R ₁₅ and ground it when recording, and there will be no problem at all. By adding the recording/playback switch, the resistance R ₁₁ , R ₁₂ ,
Resistors R _{11 and} R ₁₂ , which can eliminate R 15, are used to improve crosstalk when the left or right microphone is not connected during _recording . ₁₃ , R ₁₅ <<R ₁₄ , it goes without saying that it is unnecessary.

Effects of the Invention As described above, according to the present invention, one microphone amplifier circuit can be omitted and microphone mixing can be performed with a simple configuration.

Further, according to the present invention, the output of the mixing amplifier into which the mixing signals of the left and right microphones connected to the left and right microphone terminals are input is resistively divided into the output terminals of the left and right amplifiers whose outputs are applied to the left and right recording amplifiers. In addition, a switch installed at the output end or input end of the mixing amplifier mutes the mixing signal during recording in response to the recording/playback switch, so that the playback signals from the left and right microphones are This has the advantage that the mixed signal can be effectively muted during recording, and the influence on the outputs of the left and right amplifiers as the recording signal can be reduced to allow appropriate recording.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional tape recorder, Figure 2 is a circuit diagram of a conventional tape recorder.
The figure is a circuit diagram showing an embodiment of the tape recorder of the present invention. 11L, 11R...Magnetic head, 12L, 12
R...Preamplifier, 13L, 13R...Power amplifier, 14L, 14R...Speaker, 15L, 1
5R...Microphone terminal, 16...Mixing amplifier, _S11-1 to _S11-4 ...Record/playback switch.

Claims (1)

[Claims] 1. First and second recording/playback switches, through which the respective playback signals from the left and right magnetic heads are applied to the playback terminal, and the respective playback signals from the left and right microphones connected to the left and right microphone terminals are applied to the recording terminal; The left and right amplifiers, into which the playback signals are respectively inputted via the first and second recording/playback switches, and the left and right microphone terminals are interconnected with two resistors, and the two resistors are connected. A mixing circuit whose point is grounded through a resistor, a mixing amplifier into which the mixing signals of the left and right microphones are input from the connection midpoint of this mixing circuit, and a mixing amplifier whose output is applied to the left and right recording amplifiers. and a switch provided at the output end or input end of the mixing amplifier to mute the mixing signal during recording in response to the recording/re-switching switch. A tape recorder featuring: