JPH0441609Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an amplifier having a control circuit having a function of determining the polarity of a commercial power source.

Conventionally, commercial power sources have been connected to the ground on one end using a pole-mounted transformer, and positive and negative voltages are applied to the transformer. It is known that a potential difference occurs between the two.

It is also known that this potential difference changes depending on the direction in which the plug is inserted into the outlet.

The cause of this is an imbalance in stray capacitance that occurs between the primary winding and secondary winding of a power transformer disposed within the amplifier.

Further, this potential difference differs depending on the direction in which a power plug of an amplifier or the like is inserted into an outlet.

Therefore, in audio equipment, electrical devices such as amplifiers, tuner record players, and tape decks are used as a set, but if the power plugs of these devices are inserted in different directions, the resistance of each electrical device to the ground potential will be affected. Since the ground potentials are different and each device is connected to its shear/sea ground through an input/output connection cord, current flows through the ground line due to the difference in the shear/sea ground potential, which causes noise. This caused deterioration in sound quality.

For this reason, polarity discriminators for discriminating the polarity of electrical outlets are provided on the market, but they are not inexpensive.

Also, while checking the sound quality, the user selects the insertion direction of the power plug of each device, but this is not accurate as it depends on the sense of hearing.

Therefore, this idea uses an equalizer circuit of an amplifier such as a control amplifier, preamplifier, or integrated amplifier, and has a terminal for polarity discrimination,
The polarity determination function is provided with a simple configuration by adding a switching circuit and a level display circuit, and the embodiment shown in FIG. 1 will be described below.

In FIG. 1, 1 indicates an input stage portion of a control amplifier or preamplifier, and 2 is a signal input terminal whose + side (usually the center of the phono terminal) is connected to the first contact 3a of a switch 3.

Reference numeral 4 denotes a terminal for determining the polarity of a commercial power supply, and the minus side (usually outside the phono terminal) is connected to a shear sea earth via a resistor and a desired variable resistor 5.

That is, the negative side of the polarity determination terminal 4 is connected to the negative end of the resistance piece 5a of the variable resistor 5, and the other end of the resistance piece 5a is connected to the shear sea earth.

Also, the sliding piece 5b of the variable resistor 5 is connected to the switch 3.
The switching piece 3c of the switch 3 is connected to the switching piece 7c of the switch 7 via the equalizer amplifier 6, and the first contact 7a of the switch is connected to the next signal amplification stage (not shown). The two contacts 7b are each connected to a known level display circuit 8 using a meter or an LED, for example.

Further, 9 is a power transformer portion of the power circuit, 9a is a power switch, 10 is a power plug, 11 is an outlet, and 12 is a pole transformer.

When the switching piece 3c of the switch 3 is connected to the first contact 3a and the switching piece 7c of the switch 7 is connected to the first contact 7a, the control amplifier itself operates.

Next, the switching piece 3c of the switch 3 and the switch 7
The switching pieces 7c are the second contacts 3b and 7b, respectively.
When connected to , it exhibits a polarity discrimination function, which will be explained in detail below.

First, insert the power plug 10 into the outlet 11 and turn on the power switch 9a.

In the above state, when one side of the polarity determining terminal 4 is touched with a fingertip, one side of the polarity determining terminal 4 is connected to the ground via the human body resistance 13 .

Now, if the stray capacitance between the primary winding and the secondary winding of the power transformer 9 is unbalanced between the winding start end (the upper end of the coil in the drawing) and the winding end (the lower end of the coil in the drawing), for example, the winding The case where the starting end is larger will be described.

Insert the plug 10 into the outlet 11 in the direction shown.
When connected to, a current flows through the earth line of the secondary winding, that is, the shear sea earth, the resistor 5a, the discrimination terminal 4, and the human body resistor 13.

The value of the current in this case is proportional to the floating capacity at the beginning of the winding.

Similarly, when the plug is reversed, the earth line of the secondary winding, i.e., shear sea earth - resistor 5a
- A current flows through the discrimination terminal 4 and the human body resistance 13.

The value of the current in this case is proportional to the floating capacitance at the end of the winding.

As mentioned above, since the stray capacitance is larger at the winding start end, the level is higher at the winding start end.

As a result, the plug insertion direction is set to either the higher level or the lower level (it has been found that setting the level to a lower level is slightly better for auditory perception).

After setting the insertion direction of the plug 10 of the control amplifier 1 in this way, insert the power plug of another device, such as a tuner, into the outlet, and connect it to any input/output terminal or ground terminal with the power switch turned on. Connect the cord, connect the other end to the polarity determination terminal 4 (i.e. connect the shear/sea ground of both devices), and the level display circuit 8 in the case where the direction of the tuner power plug is reversed as described above. Set the insertion direction with a small level.

That is, in this case, the direction in which the power plug of the tuner is inserted is set to the direction in which the potential difference between the shear-sea-earth potential of the control amplifier 1 and the shear-sea-earth potential of the tuner is smaller.

Similarly, the direction of the power plugs of the record player, cassette deck, main amplifier, etc. are set to the side where the level of the level display circuit 8 is smaller.

By doing this, first, the insertion direction of the power plug 10 can be set to the side where the shear sea earth potential of the control amplifier 1 has a smaller potential difference with respect to the ground, and then the shear sea earth potential of the control amplifier 1 can be connected to the shear sea earth potential. Since the insertion direction of each power plug can be set to the side that has a smaller potential difference with the shear-sea earth potential of the equipment, the current flowing in the ground line between each equipment can be reduced.
It has excellent effects in reducing noise and preventing deterioration of sound quality.

The variable resistor shown in the embodiment is for adjusting the magnitude of the input to the equalizer amplifier 6, and if such adjustment is not required, a fixed resistor may be used.

Furthermore, the equalizer amplifier 6 has an amplification degree of about 50 dB in the low frequency region due to its RIAA characteristics, and is therefore extremely suitable for amplifying minute signals at commercial frequencies (50 Hz or 60 Hz).

In addition, in the above embodiment, the power plugs of each device were unified to the one with the lower level of the level display circuit, but the effect of this invention can be achieved even if the power plugs of each device are unified to the one with the higher level, but from experience, It is known that the audibility is better when the levels are unified to a lower level, so it is better to unify the levels to a lower level.

In this way, this invention utilizes the equalizer amplifier 6 and can provide a polarity discrimination function by simply adding a few other parts, which minimizes the cost increase and also allows the device to be installed without the need for an amplifier. It is also convenient to use.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the amplifier of this invention. 2 is a signal input terminal, 6 is an equalizer amplifier,
1 is an amplifier, 5 is a resistor, 3 and 7 are switches, and 8 is a level display circuit.

Claims (1)

[Scope of utility model registration request] In an amplifier 1 having at least a signal input terminal 2 and an equalizer amplifier, a polarity determination terminal 4 of the commercial power supply, a resistor 5 connected between the terminal 4 and the shear sea earth of the amplifier, and the signal input terminal 2 It is equipped with a switch 3 for selectively inputting the signal generated in the resistor 5 to an equalizer amplifier 6, and a switch 7 for selectively inputting the output of the equalizer amplifier 6 to the next amplification stage or level display circuit 8. The amplifier is characterized in that the level of shear-sear earth is displayed when the polarity determination terminal 4 is set to earth potential.