JPS598886B2 - Mute circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mute circuit in an 8-track, 4-channel cartridge tape player or the like.

In some of the above-mentioned cartridge tape players, etc., the rotation of the cab stan motor is stopped when the cartridge tape player is stopped, and the rotation of the cab stan motor is stopped based on the operation of the function operation button (operation button for playback, recording, fast forward, fast rewind, etc.). Some devices are configured to start driving.

Therefore, with the above configuration, the rotational speed of the capstan motor fluctuates at the start of playback, start of recording, or end of recording compared to when the rotation is steady, so there is a drawback that normal recording and playback cannot be performed. have The present invention mutes the output of the amplifier interposed in the signal transmission path during the above-described period, and when only the recording switch is operated, the muting is promptly canceled to enable source monitoring.
Furthermore, during recording and reproduction, the mute is released after the capstan motor starts up. That is, the present invention provides a tape player or the like in which the rotation of the capstan motor is started simultaneously with the recording/playback operation, and in which the start-up of the rotation of the capstan motor during the above-mentioned recording/playback operation or stop operation is applied. Alternatively, during the falling period, the output of an amplifier interposed in the signal transmission path is muted to prevent normal reproduction and recording.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 51 is a record switch among the function operation buttons described above, and 52 is a playback switch.

D1-D6 are diodes, R1-R7 are resistors, C1-
C2 is a capacitor, T1 to T3 are transistors, and A
is the above amplifier interposed in the signal transmission path. In addition,
In the above circuit, Cl and R2 constitute a differentiating circuit, and transistors Ti and T2 constitute a monomultipiperator. The period T from when a trigger is applied to the monomultipipulator until it returns to its original state through a quasi-stable state is determined by a time constant element of a capacitor C2 and a resistor R4, and is approximately T'', 0, 7C2R4.Diodes D4 and D5 constitute an OR circuit (OR circuit), and the output of the OR circuit is "H".
When the level is on, the mute transistor T3 is 0N.
state, and the output of amplifier A interposed in the signal transmission path is grounded and muted. When the output of the OR circuit is at the "L" level, the mute transistor T3 becomes 0FF, and the mute state is canceled. In the mono-multivibrator composed of the transistors T1 and T2, when power is applied (in the illustrated state), the transistor T1 is in the OFF state and the transistor T2 is in the ON state.

During reproduction, when the reproduction switch S2 is closed, a negative pulse is applied to the base of the transistor T via the capacitor C2, and the transistor T2 becomes OFF and the transistor T1 becomes ON, so that the states are reversed. . This is the metastable state of the monomultivibrator described above. That is, the transistor T2 is 0FF.
state, the diode D4 becomes conductive, the output of the OR circuit becomes 1H1 level, and the mute transistor T3 enters the ON state. Therefore, the output of amplifier A is grounded via the transistor T3 and muted. This miute period is determined to sufficiently include the rise time of the capstan motor by the time constant of capacitor C2 and resistor R4 in the circuit diagram shown in the figure.
After the time determined by the above time constant (C2XR4) has passed, the states of the transistors T1 and T2 are reversed again (T1
:0FF, T2:0N), and the above-mentioned mute is canceled. In other words, the mute mode is released after the capstan motor starts up after the regeneration operation is performed. Note that when the regeneration switch S2 is closed, the diode D
1 becomes conductive, the anode potential of the diode D5 becomes approximately 0V (ground potential), and the diode D5 becomes cut off. Next, a case will be described in which only the recording switch S1 is closed.

When the recording switch S1 is closed, the diode D1 is cut off, and the mono-multivibrator is not triggered and the transistor T2 is in the ON state.
Diode D4 enters the cut-off state. Further, at this time, the anode of the diode D5 also becomes the ground potential, so that the diode D5 is cut off. Therefore, since the output of the OR circuit composed of the diodes D4 and D5 becomes L'' level, the mute transistor T3 becomes 0FF state, and the mute state is immediately released at this time. Source monitoring is possible during recording by extracting the output of Recording is performed, and the output of the OR circuit composed of the diodes D4 and D5 causes the mute transistor T3 to be activated for a certain period of time (the time constant C2
4), and the output of the amplifier A can be muted until the capstan motor starts rotating. It goes without saying that the present invention can be applied not only to the cartridge tape player of the embodiment described above, but also to radio cassette tape recorders, etc., and can be modified in various ways without changing the gist thereof.

[Brief explanation of the drawing]

The figure is a circuit diagram showing one embodiment of the present invention.

Claims (1)

[Claims] 1. In a device in which the rotation of the capstan motor is started simultaneously by recording and reproducing operations, a series circuit consisting of a reproducing switch, a differential circuit, and a mono multivibrator, and a recording switch connected in parallel to the series circuit are used. The configured parallel circuit is connected to the mute circuit via an OR circuit, and when only the recording switch is operated, the mute operation of the mute circuit is immediately canceled, and the source can be monitored by the output of the amplifier circuit. None, a mute circuit characterized in that when the playback switch is operated or the playback switch and the record switch are operated simultaneously, a mute is applied for a certain period of time determined by the time constant of the mono-multivibrator.