JPS6327462Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a mixing circuit used in audio equipment or electronic equipment equipped with audio equipment, and in particular eliminates and saves components such as multiple switches and shielded wires compared to conventional circuits. The purpose of this invention is to provide a mixing circuit that reduces crosstalk while increasing the number of man-hours and reducing costs.

Hereinafter, examples of conventional circuits and circuits of the present invention will be explained by taking as an example a mixing circuit that can be applied to a television receiver or a stereo receiver. In the following explanation, "main audio" or "main audio channel" refers to "an audio signal originally processed by the electronic device, for example, an audio signal corresponding to the image being received by a television receiver" or ``A channel that processes the main audio'', ``sub audio'' or ``sub audio channel'' refers to an audio signal that is optionally inserted into the preamplifier stage from outside for mixing with the main audio signal, such as a microphone, etc. or a channel for processing sub-audio, respectively.

Generally, the mixing circuit is provided in the preamplifier, and an independent volume adjustment circuit is cascaded in its subsequent stage, including the main amplifier. Therefore, when the mixing switch is turned off, that is, in the mixing off mode, it is desirable that the volume for controlling the mixing level has no effect on the transmission of the main audio. Figure 1 shows
This figure represents an example of a conventional circuit that takes this point into consideration. First, FIG. 1 will be described below. In an example of an implementation circuit of the present invention, parts and components common to those in FIG.

Although the circuits in Figs. 1 and 2 show an example in which the output of a secondary audio channel S is mixed with two main audio channels _M1 and _M2 , it goes without saying that the present invention can also be applied to combinations in which the number of main and secondary audio channels is increased or decreased.

The main audio channel _M1 is directly connected to the mixing volume VR _S inserted in the sub audio channel S and the mixing volume VR _M1 which is interlocked so that its partial pressure ratio or attenuation amount is in opposite directions via the shielded wire 1. A mixing off contact 6 is connected to the main audio input terminal 2, and a mixing on contact 3 is connected to the variable voltage dividing terminal 5 of the mixing volume VR _M1 via a shielded wire 4. It is composed of a mixing switch SW _M1 and a matching amplifier 10 that operate in conjunction with a mixing switch SW _S that is connected in series to the signal path of.
Since the main audio channel _M2 has substantially the same configuration, a dash or suffix will be added to the reference numerals of the corresponding components of the main audio channel _M1 , and a description thereof will be omitted.

The sub-audio channel S includes a mixing mode changeover switch SW _S that switches between the sub-audio input terminal 11 and the no-signal terminal 12 according to the mixing on/off mode, and a sub-audio signal that is applied via the switch and a shielded wire 13. It is composed of a preamplifier 14 that amplifies the amplification, and a mixing volume VR _S that divides or attenuates its output in the opposite direction, that is, in a reciprocal manner, to the voltage division or attenuation ratio of the mixing volume VR _M1 of the main audio channel.

The output of the matching amplifier 10 of the main audio channel M ₁ and the divided voltage output of the mixing volume VR _S of the sub channel S are mixed by a mixer amplifier 30, and sent to the main amplifier as an audio preamp output via a volume (sound quality) control circuit 40. (not shown).

In such a conventional configuration, when mixing is off, the mixing switches SW _S , SW _M1 , SW _M2
Both can be switched to the position shown by the solid line, so
The preamplifier input of the sub audio channel S is cut off, and at the same time, each mixing switch SW _M1 and SW _M2 are both switched to the direct input terminal 6, 6' side, and the voltage dividing terminals of each mixing volume VR _M1 and VR _M2 are open. Therefore, the objectives of the above-mentioned mixing on and mixing off modes are achieved to a certain extent.

However, in such a configuration, wiring using expensive shielded wires is crowded around the mixing switch and volume, and the amount of connected wiring increases, which not only increases cost but also usually requires multiple installations. There are undeniable drawbacks, such as not only crosstalk and noise occurring inside the mixing switch and its vicinity, but also noise that is discarded in the sub channel when mixing is turned off.

The present invention was devised in view of the various drawbacks of the conventional example. The details will be explained below with reference to an example of an implementation circuit shown in FIG. In this example,
A variable attenuation circuit network 50 and a mixing switch circuit 60 are connected between the input terminal 2 to which the main audio signal is applied and the input terminal of the matching amplifier 10.

The variable attenuation network 50 includes a resistor 51 and capacitors 52 and 53 connected in series to the input terminal 2;
a resistor 54 connected in shunt to the signal path;
55, and a mixing volume in which all the resistors are connected between the resistors 54 and 55, and the variable terminal 56 is grounded via the mixing switching circuit 60.
Consists of VR ₁ . The switching circuit 60
The collector-emitter channel is connected between the diodes D ₁ and D ₂ whose respective anodes are connected to the variable terminals 56 and 56' of each mixing volume VR ₁ and VR ₂ , and the cathodes of both commonly connected diodes and the ground. It is comprised of a switching transistor 61 and an energizing circuit 64 which makes the switching transistor 61 conductive via resistors 62 and 63 in the mixing mode in response to switching of a mixing switch SW _S to be described later.

The sub audio channel S is composed of a preamplifier 14 and a mixing volume VR _S that variably divides the output of the preamplifier 14 and inputs it to the mixing amplifier 30.

Mixing volume of the sub-audio channel
The volume control by VR _S is the mixing volume of the mixing channel of the main audio channel.
It goes without saying that the control directions of VR ₁ and VR ₂ are set to be opposite to each other. The mixing mode changeover switch SW _S is composed of a one-circuit, two-contact switch that switches on/off the power supply to the preamplifier 14 of the subchannel and the power supply to the energizing circuit 64 .

With this configuration, if you now switch the mixing mode selector switch SW _S to the position shown by the solid line, the power supply +B
Power is supplied to the preamplifier 14 through the smoothing circuit 16, and also to an energizing circuit 64 formed by resistors 62 and 63.

Therefore, the variable divided voltage output (mixing volume output) of the sub audio channel signal is applied to the input terminal 33 of the mixing amplifier 30. On the other hand, the switching transistor 61 is conductive and both the diodes D ₁ and D ₂ are conductive, so that the variable terminals 56 and 56' of the mixing volumes VR ₁ and VR ₂ are connected to each other.
is grounded, so the main audio signal is connected to the resistors 51 and 55.
and variable resistance value of mixing volume VR ₁ (value of O ₁ P ₁ ) [resistance 5 for other main audio channels]
1', 55' and the variable resistance value (value of O ₂ P ₂ ) of the mixing volume VR ₂ ], the corresponding mixing circuits 3 are attenuated by the attenuation circuits mainly determined by
The signal is applied to the main audio input terminals 31, 31' at 0 and 30', and mixed with the sub audio signal.

When the mixing mode changeover switch SW _S is turned off (dotted line position), the power supply to the preamplifier 14 and the energizing circuit 64 is cut off. At this time, the sub-audio signal input terminals 33, 33' of the mixing amplifiers 30, 30' are bridged by a resistor between the variable terminal 17 of the mixing volume VR _S and the ground, so that no noise is input. do not have. On the other hand, the switching transistor 61 becomes non-conductive and the diodes D ₁ and D ₂ are also turned off, so that the variable terminals 56 and 5 of both mixing volumes VR ₁ and VR ₂ are turned off.
6′ are both open, both volumes VR ₁ ,
Neither VR ₂ functions as an attenuation circuit, and the main audio signal applied to input terminals 2 and 2' is a volume
It is transmitted without being affected by VR ₁ and VR ₂ , and is further added to the main audio input signal terminals 31 and 31' of the corresponding mixing amplifiers 30 and 30' through each matching amplifier 10 and 10', and is independently amplified. covered.

Instead of the switching circuit 60, an independent collector-to-emitter channel of a switching transistor is connected between the variable terminals 56, 56' of each volume VR ₁ and VR ₂ and the ground, and the base of each transistor is energized as described above. Resistor 6 of circuit 64
A configuration may be adopted in which connection is made to connection points Q of 2 and 63.

Furthermore, the switching transistor 61 may be replaced with a one-circuit, two-contact switch that is switched in conjunction with the mixing mode changeover switch _SWS .

Since the present invention has the above-mentioned configuration, parts such as shield wires and switches and their assembly man-hours can be omitted, which not only contributes to cost reduction, but also eliminates wiring congestion inside multiple switches, etc. This can greatly reduce the accompanying crosstalk.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is an implementation circuit diagram of a mixing circuit according to the present invention. _M1 , _M2 ...Main audio channel, S...Sub audio channel, VR _S , VR ₁ , VR ₂ ...Mixing volume, 60...Switching circuit, SW _S ...
Mixing mode switch.

Claims (1)

[Scope of utility model registration request] In a circuit that mixes each output of a main channel and a width channel through a variable attenuation circuit that operates in opposite directions, a variable terminal of a volume constituting the variable attenuation circuit of the main channel is grounded via a switch means. The power supply to the amplification circuit of the sub-channel is controlled by a mixing mode changeover switch that switches a mixing on/off mode, and the switch is configured to control power supply to the amplification circuit of the sub-channel in the mixing off mode. At the same time, the switch means is made non-conductive and the variable terminal of the volume is opened to minimize the amount of signal attenuation by the variable attenuation circuit of the main channel. A mixing circuit configured to supply power to an amplification circuit, conduct the switch means, ground the variable terminal of the volume, and operate the variable attenuation circuit reciprocally between the main and sub channels.