JPS6034850B2 - Level adjustment circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a level adjustment circuit suitable for, for example, a volume adjustment circuit with a recording terminal, and particularly to a level adjustment circuit that improves the load effect of its branch output.

Generally, in signal processing systems such as audio equipment, a signal line is divided into two lines, and one line is used to derive a branched output to another circuit, and the other line is connected to a reference potential point. The regulated output is often delivered to the next stage circuit.

In this case, it is undesirable to cause a so-called load effect in which the level of the branch output is varied by level adjustment of the main line. FIG. 1 shows a conventionally employed volume adjustment circuit with a recording terminal as a typical example of this type. That is, in the main line L where the signal source eIN is input to the input terminal N via the signal source resistor Rg, it is branched out to the recorder REC and is output to a predetermined value via the variable resistor VR for adjusting the volume. This is to obtain a main line signal adjusted to the signal level. Note that Rc in the figure is the input resistance of the variable resistor or non-circuit circuit in the main line. By the way, in such a circuit, the output voltage eREc derived from the recording terminal REC is as follows.

However, this is when the slider 2 of the variable resistor VR is in the recognized position, and R and N in the formula are the input resistances of the main line when viewed from the input terminal m in the direction of the arrow. , and R,2
,R. 3 is a resistance between the slider 2 and the upper end 1 and between the slider 2 and the lower end 3 of the variable resistor VR, respectively. Also"
When the slider 2 of the variable resistor VR is set to the maximum (upper end 1 side) and minimum (lower end 3 side), the branch output voltage eREc is (e fine C) skin N - branch;・e・N... It becomes 3'.

However, here Rv is the resistance of the variable resistor VR,
■In the case of formula '1}, R = 0, R23=Rv, and in the case of formula '3} [R, 2=Rv in formula 11]
, R23=0. Now, in order to see the load effect of the branch output voltage eREc given in this way and the change in the input resistance R..., Rg=20kQ, Rv=
If 100kQ (linear characteristic) and Rc = 50kQ are determined from several rotation angles taken by the slider 1 of the variable resistor VR, the result will be as shown by broken lines in FIGS. 3a and 3b, respectively.

That is, by adjusting the level with the variable resistor VR, the ratio of the branch output voltage eREc to the input voltage e,N is approximately 2.
．． It can be seen that the input resistances R and N change by about 7 degrees over a period of 33 days and 100 kQ.

For this reason, conventionally, in order to prevent the recording level and main line input impedance from changing depending on the rotation angle of the variable resistor, a buffer amplifier was inserted in order to lower the signal line impedance as much as possible, or a buffer amplifier was inserted after the variable resistor. They took measures to make the input impedance of the circuit sufficiently high.

However, such measures require complicated circuits that increase costs, and are not desirable. Therefore, the present invention has been made in view of the above points, and provides an extremely good zero-bell adjustment circuit that can reliably improve the load effect of branch output voltage with a simple circuit configuration and contribute to cost reduction. is intended to provide.

That is, the level adjustment circuit of the present invention has a value approximately equal to the input resistance of the circuit connected after the variable resistor between the slider of the variable resistor and the maximum side (input side) terminal, compared to the conventional circuit. The feature is that by connecting only one resistor, it is possible to effectively suppress variations in the branch output voltage and main line input impedance due to the position of the slider of the variable resistor. This is what we are doing. An embodiment of the present invention will be described in detail below with reference to the drawings.

That is, as shown in FIG. 2, one end of the signal sources e and N having a signal source resistance of Rg is grounded, and the end thereof is connected to the input end of the main line L.

After this input terminal IN, the main line L is branched off and connected to the recording terminal REC, and is also connected to the maximum side MAX terminal 1 of the variable resistor VR. Further, the minimum side MIN terminal 3 of this variable resistor VR is grounded and the slider 2
is connected to the next stage circuit NC having an input resistance Rc. Here, the slider 2 of the variable resistor VR and the maximum side M
Connected between the AX terminals 1 is a resistor R having a value substantially equal to the input resistance Rc of the next-stage circuit NC connected after the variable resistor VR. Note that the next stage circuit NC is generally represented by a resistance component whose input impedance is approximately Rc in a range where the frequency is not very high. In the above configuration, the branch output voltage eREc branched from the main line L and derived from the recording terminal REC is as follows.

However, this is when the slider 2 of the variable resistor VR is at an arbitrary position, and R and N in the formula are the input resistances of the main line when looking in the direction of the arrow from the input terminal m, and R,2
, R23 are resistances between the slider 2 and the maximum side MAX terminal 1 and between the slider and the minimum side MIN terminal 3 of the variable resistor VR, respectively. This is because R=Rc in the equation (2). In addition, the branch output voltage eREc is determined by connecting the variable resistor VR to the maximum side MAX terminal 1 and the minimum side M
When the melon terminal 3 is used, the relationship is as follows: shelf type = {91 formula.

However, here Rv is the resistance of the variable resistor VR,
[For formula 81, '7} In formula R, 2 = 0, R23 =
As Rv and in the equation {9}, R,2=R
v, R23=0. By the way, in order to see the load effect of the branch output voltage eREc given in this way and the changes in the input resistances R and N, the same conditions as described above, namely Rg = 20kQ, Rv = 100kQ (
However, when Rc=50kQ, R...=(R.

〆R, 2) 10 (RC〆R23) ・・・・・・(11)
When calculated from several rotation angles taken by the slider 1 of the variable resistor VR, the results are as shown by the solid lines in FIGS. 3a and 3b, respectively. That is, by adjusting the level with the variable resistor VR, the ratio of the branch output voltage eREc to the input voltage e... is approximately 1. will be subject to the load effect of B, that is, fluctuation, but this is a value that can be reduced by approximately half compared to the conventional fluctuation,
It can be seen that this can be suppressed as much as possible without causing any practical problems.

In addition, the input resistance RIN fluctuates by approximately 1 between 33 and 50kQ.
It can be seen that the change is only 7 kQ, and this can be significantly reduced to about 1'4 compared to the conventional change. Since the fluctuations in the input resistances R and N can be suppressed as much as possible in this way, the frequency characteristics given to the signal depending on the position of the variable resistor VR, due to the stray capacitance of the signal source, that is, the frequency characteristics of this embodiment. In this case, the negative impact on sound quality can be effectively reduced.

Note that the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention. Therefore, according to the level adjustment circuit as described above, unlike the conventional circuit, the input resistance of the circuit connected to the variable resistor is connected between the slider of the variable resistor and the maximum side (input side) terminal. By simply connecting only one resistor with a value approximately equal to that of the variable resistor, the branch output voltage and the input impedance of the main line can be adjusted by connecting a single resistor with a value approximately equal to that of the variable resistor. Fluctuations depending on the child's position can be effectively suppressed. As detailed above, according to the present invention, the branch output voltage load effect can be reliably improved with a simple circuit configuration.
This makes it possible to provide an extremely good bell adjustment circuit that can contribute to cost reduction.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram showing a conventional volume control circuit with a recording terminal.
Figure 2 is a wiring diagram showing a volume adjustment circuit with a recording terminal as an embodiment of the level adjustment circuit according to the present invention, and Figures 3a and b.
1 is a change characteristic curve diagram of branch output voltage and input resistance according to the present invention shown in comparison with the conventional one. e, N...signal source, Rg...signal source resistance, IN...input terminal, REC...recording terminal, VR.・・・・・・Variable resistor, Rc・・・・・・
・Input resistance, NC...Next stage circuit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A signal line is divided into two, and a branch output is derived from one line to another circuit, and a level adjustment output is derived from the slider of a variable resistor whose both ends are connected between the other line and a reference potential point to the next stage circuit. 1. A level adjustment circuit comprising: a resistor having a value substantially equal to the input resistance of the next stage circuit is connected between one end of the variable resistor and the slider.