JPS581854Y2 - tape recorder circuit - Google Patents

Description

[Detailed description of the invention] This invention relates to a tape recorder circuit that records a built-in microphone output signal, an external microphone output signal button, and a preliminary input signal input to a preliminary input terminal. When recording, the operation of the built-in microphone is stopped, and mixing recording of the built-in microphone output signal and the preliminary input signal and mixing recording of the built-in microphone output signal and external microphone output signal are prevented, and mixing recording using the built-in microphone output signal is prevented. Preventing failed recordings, and
The preliminary input signal is directly input to the output amplifier, and the weak external microphone output signal is first amplified by the recording amplifier and then input to the output amplifier.
It is an object of the present invention to provide a tape recorder circuit which can perform high S/N monitoring of a preliminary input signal and can appropriately monitor an external microphone output signal.

FIG. 1 shows a conventional tape recorder circuit, in which AUX is an auxiliary input terminal consisting of a jack, etc., into which a auxiliary input signal from an external signal source is input.

R1 is the input resistance connected to the preliminary input terminal AUX, BM
is a built-in microphone that is activated by the application of power supply B, R2 is an input resistor connected to the built-in microphone BM, and EM is an external microphone input terminal consisting of a jack, etc., into which the output signal of the external microphone, that is, the external microphone output signal is input. Ru.

R3 is a resistor that divides the output signal of the auxiliary input terminal button and the built-in microphone BM via the auxiliary input terminal AUX, that is, the built-in microphone output signal, and its resistance value is equal to the input impedance of the external microphone.

RA is a recording amplifier that amplifies the preliminary input signal via the resistor R1, the built-in microphone output signal via the resistor R2, and the external microphone output signal from the external microphone input terminal EM via the resistor R3, and SL is the built-in microphone BM. A changeover switch S2 for controlling the application of the power source B to the recording amplifier RA is interlocked with the switch S, and when the switch S is switched to the off contact OFF and the power source B is applied to the built-in microphone BM. VR is a monitor volume controller connected to the switch terminal of the monitor switch S2, and MA is the volume controller V.
R is the output amplifier connected to it, SP is the monitor speaker connected to the output amplifier MA, and RP is the recording amplifier RA.
The recording/reproducing head BO connected to is a bias oscillator that supplies an oscillation signal to the recording/reproducing head RP.

When the switch S is switched to the off contact OFF, the circuit between the built-in microphone BM and the power supply terminal B is opened, the power supply terminal B is no longer applied to the built-in microphone BM, and the built-in microphone BM no longer operates. Auxiliary input terminal AUX
Insert the plugs of the external signal source and external microphone into the AUX and external microphone input terminals EM, respectively, and input the preliminary input signal and external microphone output signal to the preliminary input terminal AUX and the external microphone input terminal EM, respectively, and the preliminary input signal and external microphone output signals are each amplified by the recording amplifier RA and sent to the recording/playback head RP.
and the preliminary input signal and external microphone output signal are respectively recorded.

On the other hand, when the switch S1 is switched to the off contact OFF, the switch S2 is also switched to the off contact OFF, a circuit is closed between the recording amplifier RA and the volume controller VR, and the preliminary input signal and the Each of the external microphone output signals is input to the output amplifier MA via the volume controller VR, and the preliminary input signal and the external microphone output signal are monitored by the output signal of the output amplifier MA.

Note that by switching a mixing switch (not shown), mixing recording of the preliminary input signal and the external microphone output signal can be performed.

By the way, since the signal level of an external microphone signal is generally weak, it is impossible to directly input the external microphone signal to the output amplifier MA and monitor it with the speaker SP, but the preliminary input signal can be output amplified! The signal level is set so that it can be input directly to the MA and monitored by the speaker SP.

In the above case, the preliminary input signal is also input to the output amplifier MA via the recording amplifier RA, so when the preliminary input signal is monitored by the speaker SP, the recording amplifier R
There is a drawback that the noise generated by A itself is added to the unavoidable preliminary input signal, and the S/N of the monitor output is degraded.

Next, when the switch S1 is turned on, the power supply B is applied to the built-in microphone BM, the built-in microphone BM is activated, and the built-in microphone output signal is amplified by the recording amplifier RA and supplied to the recording/playback head RP. The built-in microphone output signal is recorded.

On the other hand, when the switch S1 is switched to the ON contact ON, the switch S2 is also switched to the ON contact ON, and the circuit between the recording amplifier RA and the volume controller VR is opened, so the built-in microphone output signal cannot be monitored by the speaker SP. do not have.

That is, when the built-in microphone BM is activated, there is a possibility that the built-in microphone BM may pick up the monitor output from the speaker SP and cause howling, so the switch S2 is linked to the switch S1 to disable monitoring by the speaker SP.

However, since opening and closing between the built-in microphone BM and the power supply element B is performed by switching the switch S1, if you forget to switch the off contact of switch S1 to OFF after using the built-in microphone, the external microphone output signal When recording the button and preliminary input signals, there is a risk that recording failures such as unnecessary signals being mixed may occur.

This idea was made with the above points in mind,
Next, this invention will be explained with reference to FIG. 2 showing one embodiment thereof.

In Figure 2, in addition to the symbols used in Figure 1, R4, R
5 is a dividing resistor that divides the auxiliary input signal of the auxiliary input terminal AUX and supplies it to the monitor volume controller VR, and S3 is a built-in microphone that switches to ON contact when an external signal source is connected to the auxiliary input terminal AUX. The preliminary input switch S4 opens the circuit between BM and power supply B, and when an external microphone is connected to the external microphone input terminal EM, the on contact turns ON, and the off contact OF the built-in microphone BM and switch S3 turns ON.
This is an external microphone switch that opens a circuit between the power source B and the power source B via F, and the off contact OFF is connected to the built-in microphone BM.

Q is an NPN transistor whose collector is resistor R6.
It is connected to the output terminal of the recording amplifier RA via a resistor R7, its base is connected to the ON contact of the switch S4 via a resistor R7, and its emitter is connected to a volume controller VR.

Note that the signal level of the preliminary input signal is set to approximately -20 dB, and the signal level of the external microphone output signal is approximately -70 dB.
is set to .

And external microphone input terminal EM Muyo and auxiliary input terminal AU
Insert the external microphone and external signal source plugs into each of the X and switch S3. S4 is held at the off contact OFF, the circuit between the built-in microphone BM and the power supply 1B is closed, the power supply 1B is applied to the built-in microphone BM, the built-in microphone BM is activated, and the built-in microphone output signal is sent to the recording amplifier RA. The signal is output to the recording/reproducing head RP via the recording/reproducing head RP.

On the other hand, since the switch S4 is held at the off contact OFF, the transistor Q is held non-conductive, and the built-in microphone output signal via the recording amplifier RA is not input to the output amplifier MA, and the built-in microphone output signal is output from the speaker SP. cannot be monitored by

Next, when the plug of the external signal source is inserted into the auxiliary input terminal AUX and the external signal source is connected to the auxiliary input terminal AUX, the auxiliary input switch S3 is switched to the ON contact ON,
The circuit between the built-in microphone BM and the power supply 1B is opened, and the power supply 1B is no longer applied to the built-in microphone BM, and the preliminary input signal is sent to the recording/reproducing head R via the resistor R1 and the recording amplifier RA.
Recorded by P.

In addition, an auxiliary input terminal AUX divided by resistors R4 and R5
The preliminary input signal is directly input to the output amplifier MA via the volume controller VR, and at this time, since the level of the preliminary input signal is set to a large level of 120 dB, the preliminary input signal via the output amplifier MA is input directly to the output amplifier MA. The signal is monitored at speaker SP.

And the preliminary input signal monitored by speaker SP is
Since it does not go through the recording amplifier RA, the S/N of the monitor output is
is significantly improved by more than 10 dB compared to the circuit shown in Figure 1, allowing high S/N monitoring, and since 10B of power is not applied to the built-in microphone BM, the preliminary input signal and the built-in microphone output are There is no possibility of recording failure due to signal mixing.

Insert the plug of the disconnected external signal source into the auxiliary input terminal AUX, insert the plug of the external microphone into the external microphone input terminal EM, and connect the external microphone to the external microphone input terminal EM, the external microphone switch S4 turns on contact. When the switch is turned ON, the connection between the built-in microphone BM and the power supply 1B is opened and the power supply 1B is no longer applied to the built-in microphone BM, and the external microphone output signal is amplified by the recording amplifier RA and recorded. output to the recording/reproducing head RP.
The external microphone output signal is recorded.

On the other hand, since the external microphone switch S4 is switched to the ON contact ON, the power supply 1B is applied to the ON contact of the switch S, and to the base of the transistor Q via the resistor R7, and the transistor Q becomes conductive. The external microphone output signal amplified in the previous stage is output from the output of the transistor Q via the sound regulator VR to the output amplifier MA, and the external microphone output signal further amplified by the output amplifier MA is monitored by the speaker SP. be done.

The external microphone output signal, which has a low input level, is first amplified by the recording amplifier RA and then further amplified by the output amplifier MA. Since the power supply voltage of 10B is not applied to the BM, there is no possibility of failure of the external microphone output signal and the built-in microphone output signal causing kissing recording.

As described above, the tape recorder circuit of this invention prevents mixing recording between the built-in microphone output signal and the preliminary input signal and mixing recording between the built-in microphone output signal and the external microphone output signal, and prevents mixing recording between the built-in microphone output signal and the external microphone output signal. Mixing failure recording can be prevented, and the preliminary input signal is directly input to the output amplifier, and the external microphone output signal is pre-amplified by the recording amplifier and then input to the output amplifier. It is possible to monitor N.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of a conventional tape recorder circuit, and FIG. 2 is a wiring diagram of an embodiment of the tape recorder circuit of this invention. AUX: Auxiliary input terminal, RA: Recording amplifier, EM: External microphone input terminal, BM
...Built-in microphone, MA... Output amplifier, R4, R5... Dividing resistor, VR...
Volume adjuster, 10B...Power supply, S3...
Auxiliary input switch, S4...external microphone switch, Q...transistor.

Claims (1)

[Scope of utility model registration request] The built-in microphone output signal of the built-in microphone activated by the application of power, the external microphone output signal of the external microphone via the external microphone input terminal consisting of a jack, etc., and the backup signal from an external signal source via the auxiliary input terminal consisting of a jack etc. It includes a recording amplifier that amplifies each input signal and outputs it to the recording head, and connects the external microphone to the external microphone input terminal and connects the external signal source to the auxiliary input terminal to connect the built-in microphone and the recording head. an external microphone switch and an auxiliary input switch that open a circuit between the built-in microphone and the power supply; and an external microphone switch that conducts the external microphone output signal via the recording amplifier only when the built-in microphone and the power supply are opened. A tape recorder circuit comprising: a transistor for outputting; and an output amplifier for amplifying the preliminary input signal and the external microphone output signal output from the transistor and supplying the amplified signals to a monitor speaker.