Amplifier

Abstract

Suppresses noise caused by filament vibration. [Solution] The amplification device of the present invention comprises an amplification unit, a vacuum tube, an input unit, an output unit, and a negative feedback unit. The amplification unit outputs an amplified input signal obtained by amplifying the input signal. The vacuum tube has a filament that emits thermionic electrons, a grid, and an anode. The input unit inputs a biased input signal to the grid, which is obtained by adding a bias voltage to the component corresponding to the AC component of the amplified input signal. The output unit outputs the signal output from the anode via a buffer circuit. The negative feedback unit negatively feeds back the output from the buffer circuit to the grid. The amplification factor with the configuration of a vacuum tube, input unit, output unit, and negative feedback unit is smaller than the amplification factor of the vacuum tube when there is no negative feedback unit.

Description

[Technical Field]

[0001] The present invention relates to an amplification device having a vacuum tube. [Background technology]

[0002] Techniques for distorting musical tones using vacuum tubes are known, as described in Patent Documents 1 and 2, and Non-Patent Document 1. Compared to conventional vacuum tubes, the vacuum tubes described in these documents have advantages such as low power consumption, small size, long lifespan, and low heat generation, and can be directly mounted on a substrate like an LSI. However, there is a problem in that the vibration of the filament easily affects the amplification characteristics. Techniques for suppressing the effect of filament vibration on amplification characteristics are known, as described in Patent Documents 3 and 4. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-134299 [Patent Document 2] Japanese Patent Publication No. 2021-100212 [Patent Document 3] International Publication No. 2019 / 139074 [Patent Document 4] Registered Utility Model No. 3207389 Gazette [Non-patent literature]

[0004] [Non-Patent Document 1] KORG, “Nutube”, [Retrieved November 28, 2024], Internet<https: / / korgnutube.com / jp / > . [Overview of the project] [Problems that the invention aims to solve]

[0005] The technologies of Patent Documents 3 and 4 are both technologies for mechanically suppressing the vibration of the filament. In order to further suppress the noise (microphonic noise) caused by the vibration of the filament, a technology that can be combined with these technologies is required. The present invention aims to suppress the noise caused by the vibration of the filament.

Means for Solving the Problems

[0006] The amplification device of the present invention includes an amplification unit, a vacuum tube, an input unit, an output unit, and a negative feedback unit. The amplification unit outputs an amplified input signal obtained by amplifying an input signal. The vacuum tube has a filament that emits thermoelectrons, a grid, and an anode. The input unit inputs a bias input signal obtained by adding a bias voltage to a component corresponding to the AC component of the amplified input signal to the grid. The output unit outputs the signal output from the anode via a buffer circuit. The negative feedback unit performs negative feedback of the output from the buffer circuit to the grid. The amplification factor in the configuration of the vacuum tube, the input unit, the output unit, and the negative feedback unit is smaller than the amplification factor of the vacuum tube when there is no negative feedback unit.

Effects of the Invention

[0007] The noise caused by the vibration of the filament is superimposed on the input signal without depending on the amplitude of the signal input to the vacuum tube. Therefore, if the amplitude of the signal input to the vacuum tube is increased, the SN ratio is improved. According to the amplification device of the present invention, the amplification factor in the configuration of the vacuum tube, the input unit, the output unit, and the negative feedback unit is smaller than the amplification factor of the vacuum tube when there is no negative feedback unit. The required amplification factor of the amplification device is determined by the amplification factor of the amplification unit and the amplification factor in the configuration of the vacuum tube, the input unit, the output unit, and the negative feedback unit. Since the amplification unit amplifies the input signal, the amplitude of the signal input to the vacuum tube becomes large. Therefore, the amplification device of the present invention can suppress the noise (microphonic noise) caused by the vibration of the filament.

Brief Description of the Drawings

[0008] [Figure 1] A diagram showing a functional configuration example of the amplification device of Example 1. [Figure 2]Fig. showing the configuration example of the vacuum tube amplification section of Example 1 and Modified Example 1. [Figure 3] Fig. showing the configuration example of the vacuum tube amplification section 120, input section 130, output section 140, and negative feedback section 150 of Example 1. [Figure 4] Fig. showing the configuration example of the vacuum tube amplification section 120, input section 130, output section 140, and negative feedback section 150 of Modified Example 1. [Figure 5] Fig. showing the frequency characteristics of the pre-emphasis circuit and de-emphasis circuit. [Figure 6] Fig. showing the functional configuration example of the amplification device of Modified Example 2. [Figure 7] Fig. showing the configuration example of the vacuum tube amplification section of Modified Example 2, Modified Example 3, and Modified Example 4. [Figure 8] Fig. showing the functional configuration example of the amplification device of Modified Example 3. [Figure 9] Fig. showing the functional configuration example of the amplification device of Modified Example 4.

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail. Components having the same function are given the same number, and redundant explanations are omitted.

Example

[0010] Fig. 1 shows a functional configuration example of the amplification device of Example 1. The amplification device 100 includes an amplification section 110, a vacuum tube amplification section 120, an input section 130, an output section 140, and a negative feedback section 150. The amplification section 110 has an amplification circuit 111 and outputs an amplified input signal S in obtained by amplifying the input signal s. The amplification factor of the amplification section 110 is desirably set to the amplification factor required for the amplification device 100. In this case, the amplification factor in the configuration of the vacuum tube 121, input section 130, output section 140, and negative feedback section 150 may be set to 1. However, as will be described later, if the amplification factor in the configuration of the vacuum tube 121, input section 130, output section 140, and negative feedback section 150 is set smaller than the amplification factor of the vacuum tube 121 when the negative feedback section 150 is not present, an effect of suppressing noise (microphonic noise) due to the vibration of the filament 122 can be obtained.

[0011] FIG. 2 shows a configuration example of the vacuum tube amplification section. The vacuum tube amplification section 120 includes a vacuum tube 121 having a filament 122 that emits thermoelectrons, a grid 123, and an anode 124. One end of the filament 122 is connected to a grounded terminal 120 G and the other end is connected to a power supply terminal 120 F . A voltage V F is applied to the terminal 120 F , and the filament 122 is heated to about 650 degrees, for example, to emit thermoelectrons. The grid 123 is connected to a terminal 120 in for the signal input to the vacuum tube amplification section 120. The anode 124 is connected to a terminal 120 out for the signal output from the vacuum tube amplification section 120, and is also connected to a power supply terminal 120 v via a resistor 125. A supply voltage CV is applied to the terminal 120 v . For the vacuum tube 121, the vacuum tubes shown in Patent Document 1 and Non-Patent Document 1 may be used. In the case of the vacuum tube shown in Non-Patent Document 1, the gain of the vacuum tube 121 can be set by setting the supply voltage CV. For example, when the supply voltage CV is set to 12 V, the amplification factor of the vacuum tube amplification section 120 itself can be made about 14 dB. This amplification factor corresponds to the amplification factor of the vacuum tube 121 when the negative feedback section 150 is not present. The resistor 125 may be, for example, 220 kΩ.

[0012] FIG. 3 shows a configuration example of the vacuum tube amplification section 120, the input section 130, the output section 140, and the negative feedback section 150 of the first embodiment. The input section 130 inputs a bias input signal S bias obtained by adding a bias voltage V bin corresponding to the AC component of the amplified input signal to the grid 123. More specifically, the input section 130 may include a capacitor 131 and two resistors 132 and 133. The capacitor 131 serves to cut the DC component of the amplified input signal and transmit the AC component. For example, the capacitor 131 may be 10 μF. The bias voltage V bias is added via the resistor 133. If it is not connected to the vacuum tube amplification section 120, the amplified input signal S inThe AC component is divided by resistors 132 and 133. For example, if resistors 132 and 133 are set to the same resistance value (e.g., 33kΩ), then the amplified input signal S will be divided when it is not connected to the vacuum tube amplifier section 120. in The voltage with half the amplitude of the AC component is the bias input signal S. bin This is the result. In this case, the amplified input signal S in A voltage with half the amplitude of the AC component corresponds to the "component corresponding to the AC component of the amplified input signal". In reality, since it is connected to the vacuum tube amplifier section 120, the bias input signal S bin Even if you observe the amplified input signal S in A voltage with half the amplitude of the AC component cannot be observed. However, the amplified input signal S is detected at the grid 123 of the vacuum tube amplifier section 120. in It is influencing the signal with a voltage having half the amplitude of the AC component.

[0013] The output unit 140 outputs the signal output from the anode 124 via the buffer circuit 141. The output unit 140 also outputs an output signal via the resistor 142. The buffer circuit 141 may use a field-effect transistor (FET) or an operational amplifier. The resistor 142 can be set to, for example, about 10kΩ.

[0014] The negative feedback section 150 feeds back the output from the buffer circuit 141 to the grid 123. The amplification factor of the configuration consisting of the vacuum tube 121, input section 130, output section 140, and negative feedback section 150 should be set to be smaller than the amplification factor of the vacuum tube 121 when the negative feedback section 150 is absent. Noise due to the vibration of the filament 122 is superimposed on the input signal, independent of the amplitude of the signal input to the vacuum tube 121. Therefore, increasing the amplitude of the signal input to the vacuum tube 121 improves the signal-to-noise ratio. The amplification factor required for the amplifier 100 is determined by the amplification factor of the amplifier section 110 and the amplification factor of the configuration consisting of the vacuum tube 121, input section 130, output section 140, and negative feedback section 150. Since the amplifier section 110 amplifies the input signal, the amplitude of the signal input to the vacuum tube 121 becomes larger.

[0015] The amplification factor of the amplifier 110 should be set so that the amplification factor of the configuration consisting of the vacuum tube 121, input section 130, output section 140, and negative feedback section 150 is smaller than the amplification factor of the vacuum tube 121 when the negative feedback section 150 is absent. By setting it in this way, the amplifier 100 can suppress noise (microphonic noise) caused by the vibration of the filament 122. In particular, if the amplification factor required for the amplifier 100 is set in the amplifier 110, and the vacuum tube 121, input section 130, output section 140, and negative feedback section 150 are set to function as a buffer (amplification factor of 1), it is easier to suppress noise (microphonic noise) caused by the vibration of the filament 122. Furthermore, the amplifier 100 can also be combined with the techniques for suppressing mechanical noise (microphonic noise) described in Patent Documents 3 and 4.

[0016] The negative feedback section 150 only needs to include a capacitor 151 to remove the DC component and a resistor 152 to determine the amplification factor. For example, capacitor 151 can be 10μF. Also, if the vacuum tube 121, input section 130, output section 140, and negative feedback section 150 are to function as a buffer (amplification factor of 1), then for example, resistors 132 and 133 can be set to the same resistance value (e.g., 33kΩ), and resistor 152 can be set to twice the resistance value of resistor 132 (e.g., 66kΩ). However, the specific resistance values ​​may be other than those exemplified.

[0017] Since the purpose of the amplifier 100 is to obtain the characteristics of the vacuum tube 121, the amplification unit 110 should output an amplification input signal that makes it easy to obtain the characteristics of the vacuum tube 121. Therefore, the amplification factor required for the amplifier 100 should be an amplification factor that makes it easy to obtain the characteristics of the vacuum tube 121. The power required for the signal to be output from the speaker or the like can be obtained by further processing, such as amplifying the output from the amplifier 100. [Example 1]

[0018] Figure 4 shows an example configuration of the vacuum tube amplifier section 120, input section 130, output section 140, and negative feedback section 150 of Modification 1. In Modification 1, the input section 130 has a pre-emphasis circuit 135, and the negative feedback section 150 has a de-emphasis circuit 155. Figure 5 shows the frequency characteristics of the pre-emphasis circuit and the de-emphasis circuit. Figure 5(A) shows the frequency characteristics of the pre-emphasis circuit 135, and Figure 5(B) shows the frequency characteristics of the de-emphasis circuit. In both figures, the horizontal axis is frequency and the vertical axis is gain. The pre-emphasis circuit 135 increases the gain at frequencies above the fundamental frequency of the natural vibration of the filament 122. The de-emphasis circuit 155 has characteristics opposite to those of the pre-emphasis circuit 135.

[0019] Both the pre-emphasis circuit 135 and the de-emphasis circuit 155 can be, for example, equipped with capacitors 136 and 156 and resistors 137 and 157. For example, if the fundamental frequency of the natural vibration of the filament 122 is around 5 kHz, then in the circuit shown in Figure 4, capacitor 131 should be 0.75 μF, capacitor 136 0.01 μF, resistor 137 20 kΩ, capacitor 156 0.0066 μF, and resistor 157 33 kΩ. The pre-emphasis circuit 135 and the de-emphasis circuit 155 are not limited to the circuits shown in Figure 4. Also, the fundamental frequency of the natural vibration of the filament is not limited to 5 kHz; it could be 4 kHz, for example. The pre-emphasis circuit 135 should increase the gain at frequencies above the fundamental frequency of the natural vibration of the filament 122, and the de-emphasis circuit 155 should have characteristics opposite to those of the pre-emphasis circuit 135. Since the amplification input signal can be increased at the fundamental frequency of the filament 122's natural vibration, it is easier to suppress noise (microphonic noise) caused by the vibration of the filament 122 than in Example 1. Also, by increasing the amplification input signal at frequencies above the fundamental frequency, it is easier to suppress noise caused by second and third harmonics. Except for the above explanation, it is the same as Example 1. [Differentiation 2]

[0020] Figure 6 shows an example of the functional configuration of the amplifier in Modification 2. Figure 7 shows an example of the configuration of the vacuum tube amplifier in Modification 2. The amplifier 200 comprises an amplification unit 110, an inverting unit 210, vacuum tube amplification units 120, 220, input units 130, 230, output units 140, 240, negative feedback units 150, 250, and a differential amplifier unit 260. The amplification unit 110, input unit 130, output unit 140, and negative feedback unit 150 are the same as in Embodiment 1. The inverting unit 210 receives the amplification input signal S in The inverted amplified input signal S has its phase reversed. -in Outputs.

[0021] The vacuum tube amplifiers 120 and 220 can use a vacuum tube 221 having two sets of grids and anodes. Specifically, the vacuum tubes shown in Patent Document 1 and Non-Patent Document 1 can be used. This vacuum tube has two sets of filaments 122 and 222, two sets of grids 123 and 223, and two sets of anodes 124 and 224 within a single vacuum tube 221. The filament 122 is connected to terminal 120 F and terminal 220 G During this time, the filament 222 is at terminal 220 F and terminal 220 G It is positioned between terminals 120 F and terminal 220 F Voltage V F The signal is applied to terminal 220 G It is grounded. The filaments 122 and 222 are heated to, for example, about 650 degrees Celsius and emit thermionic electrons. Alternatively, one filament may be shared by two sets of grids and anodes. Grid 123 is connected to terminal 120 for signals input to the vacuum tube amplifier 120. in It is connected to the terminal 220 for the signal input to the vacuum tube amplifier section 220. in It is connected to terminal 120 for the signal output from the vacuum tube amplifier section 120. out It is connected to the power supply terminal 120 via resistor 125. v It connects to terminal 120. v A supply voltage CV is applied to it. Anode 224 is terminal 220 for the signal output from the vacuum tube amplifier section 220. outIt is connected to the power supply terminal 220 via resistor 225. v It connects to terminal 220. v A supply voltage CV is applied to this. In the case of the vacuum tube shown in Non-Patent Document 1, the gain of the vacuum tube 221 can be set by setting the supply voltage CV. For example, if the supply voltage CV is set to 12V, the amplification factor of the vacuum tube amplifier section 120,220 itself can be set to about 14dB. This amplification factor corresponds to the amplification factor of the vacuum tube 221 when the negative feedback section 150,250 is absent. Resistors 125,225 can be set to, for example, 220kΩ.

[0022] The input section 230 applies a bias voltage V to the component corresponding to the AC component of the inverting amplifier input signal. bias The bias-inverted input signal S with added bias -bin The signal is input to grid 223. The specific configuration of input section 230 is the same as that of input section 130 (see Figure 3). Output section 240 outputs the signal output from anode 224 via a buffer circuit. Output section 240 also outputs an output signal via a resistor. The specific configuration of output section 240 is the same as that of output section 140 (see Figure 3). Negative feedback section 250 provides negative feedback from the buffer circuit to grid 223. The specific configuration of negative feedback section 250 is the same as that of negative feedback section 150 (see Figure 3).

[0023] As described above, the output signal from output unit 140 and the output signal from output unit 240 are inverted in phase. The differential amplifier unit 260 outputs the difference between the output signal from output unit 140 and the output signal from output unit 240. If the noise contained in the output signal from output unit 140 and the noise contained in the output signal from output unit 240 are in phase, the differential amplifier unit 260 will suppress the noise. The amplifier 200 includes the same configuration as the amplifier 100 of Embodiment 1, so the same effect can be obtained. Furthermore, the amplifier 200 uses vacuum tubes arranged in the same housing and outputs a signal corresponding to the difference in output from the anodes, so it has advantages such as being able to remove in-phase noise (noise applied equally to both vacuum tubes). Moreover, the amplifier 200 can be combined with the techniques for suppressing mechanical noise (microphonic noise) described in Patent Documents 3 and 4. [Difference 3]

[0024] Figure 8 shows an example of the functional configuration of the amplifier of Modified Example 3. In Modified Example 3, the input section 130 has a pre-emphasis circuit 135, the input section 230 has a pre-emphasis circuit 235, the negative feedback section 150 has a de-emphasis circuit 155, and the negative feedback section 250 has a de-emphasis circuit 255. The pre-emphasis circuit 135 and the pre-emphasis circuit 235 have the same characteristics and increase the gain at frequencies above the fundamental frequency of the natural vibration of the filaments 122 and 222. The de-emphasis circuit 155 and the de-emphasis circuit 255 have the same characteristics and have characteristics opposite to those of the pre-emphasis circuits 135 and 235. Except for the above explanation, it is the same as Modified Example 2. The amplifier 200 of Modified Example 3 can increase the amplification input signal at the fundamental frequency of the natural vibration of the filaments 122 and 222, so it is easier to suppress noise (microphonic noise) caused by the vibration of the filaments 122 and 222 than in Modified Example 2. [Differentiation Example 4]

[0025] Figure 9 shows an example of the functional configuration of the amplifier in Modification 4. Modification 4 differs from Modification 3 in that the differential amplifier section 260 has a de-emphasis circuit 265 instead of the negative feedback sections 150 and 250. The de-emphasis circuit 265 has characteristics opposite to those of the pre-emphasis circuits 135 and 235, while also considering differential amplification. The amplifier 200 of Modification 4 can also increase the amplification input signal at the fundamental frequency of the natural vibration of the filaments 122 and 222, making it easier to suppress noise (microphonic noise) caused by the vibration of the filaments 122 and 222 than in Modification 2. [Explanation of symbols]

[0026] 100 Amplifier 110 Amplifier section 111 Amplification circuit 120 Vacuum tube amplification section 120,220 Vacuum tube amplifier section 121,221 Vacuum tubes 122,222 filaments, 123,223 grids 124,224 anode, 125,225 resistor 130,230 Input section 131, 136, 151, 156 Capacitors 132, 133, 137, 142, 152, 157 resistors 135,235 Pre-emphasis circuits 140,240 Output section 141 Buffer circuit 150,250 Negative feedback section 155,255,265 de-emphasis circuit 200 Amplifier 210 Inverter 260 Differential Amplifier Section

Claims

1. An amplification unit that outputs an amplified input signal obtained by amplifying the input signal, A vacuum tube having a filament that emits thermionic electrons, a grid, and an anode, An input unit that inputs a bias input signal to the grid, which is obtained by adding a bias voltage to the component corresponding to the AC component of the amplified input signal. The output unit outputs the signal output from the anode via a buffer circuit, A negative feedback unit that feeds back the output from the buffer circuit to the grid. Equipped with, The amplification factor in the configuration of the vacuum tube, the input section, the output section, and the negative feedback section is smaller than the amplification factor of the vacuum tube when the negative feedback section is absent. An amplification device characterized by the following features.

2. An amplification unit that outputs an amplified input signal obtained by amplifying the input signal, A vacuum tube having a filament that emits thermionic electrons, a grid, and an anode, An input unit that inputs a bias input signal to the grid, which is obtained by adding a bias voltage to the component corresponding to the AC component of the amplified input signal. The output unit outputs the signal output from the anode via a buffer circuit, A negative feedback unit that feeds back the output from the buffer circuit to the grid. Equipped with, The vacuum tube, the input section, the output section, and the negative feedback section function as buffers. An amplification device characterized by the following features.

3. An amplification device according to claim 1 or 2, The input section also includes a pre-emphasis circuit that increases the gain at frequencies above the fundamental frequency of the filament's natural vibration. The negative feedback section also includes a de-emphasis circuit having characteristics opposite to those of the pre-emphasis circuit. An amplification device characterized by the following features.

4. An amplification unit that outputs an amplified input signal obtained by amplifying the input signal, An inverting unit that outputs an inverted amplified input signal obtained by inverting the phase of the amplified input signal, A vacuum tube having a filament that emits thermionic electrons, two sets of grids and anodes, A first input unit inputs a bias input signal, which is obtained by adding a bias voltage to the component corresponding to the AC component of the amplified input signal, to one set of grids. A second input unit inputs a biased inverted input signal, obtained by adding a bias voltage to the component corresponding to the AC component of the inverted amplifier input signal, to the grid of the other set. A first output unit outputs the signal output from one of the anodes via a buffer circuit, A second output unit outputs the signal output from the anode of the other pair via a buffer circuit, A first negative feedback unit that negatively feeds back the output from the buffer circuit of the first output unit to the grid of one of the pairs, A second negative feedback unit that negatively feeds back the output from the buffer circuit of the second output unit to the grid of the other set, A differential amplifier that outputs a signal corresponding to the difference between the output of the first output unit and the output of the second output unit. Equipped with, The vacuum tube, the first input section, the first output section, and the first negative feedback section function as a buffer. The vacuum tube, the second input section, the second output section, and the second negative feedback section function as buffers. An amplification device characterized by the following features.

5. The amplification device according to claim 4, The first input section and the second input section also include a pre-emphasis circuit that increases the gain at frequencies above the fundamental frequency of the filament's natural vibration. The first negative feedback section and the second negative feedback section also include a de-emphasis circuit having characteristics opposite to those of the pre-emphasis circuit. An amplification device characterized by the following features.

6. The amplification device according to claim 4, The first input section and the second input section also include a pre-emphasis circuit that increases the gain at frequencies above the fundamental frequency of the filament's natural vibration. The differential amplifier section also includes a de-emphasis circuit having characteristics opposite to those of the pre-emphasis circuit. An amplification device characterized by the following features.

Images