JP6281814B2 - Speaker-driven negative feedback amplifier - Google Patents

Description

The present invention relates to a speaker-driven negative feedback amplifier, and relates to an amplifier that improves sound quality including a negative feedback circuit of a power negative feedback amplifier and a resistor constituting the negative feedback circuit.

Nowadays, a typical speaker-driven amplifier uses a voltage-driven negative feedback amplifier. In this system, the speaker is outside the negative feedback closed loop and is a simple load.

On the other hand, a speaker-driven negative feedback amplifier driven by current is an excellent system that does not include an imaginary part because a constant current flows through a speaker. However, a negative feedback resistor has a problem in sound quality and is not widespread.

JP-A-8-32360

In the speaker current drive negative feedback amplifier, a current sufficient to take a heat dissipation flows through the speaker current detection resistor constituting the negative feedback circuit to generate heat. Therefore, it consists of enamel resistance and cement resistance with high heat dissipation effect. However, due to the heating action of the resistor, the resistance value changes irregularly, or thermal distortion occurs due to partial uneven heat transfer. Since this thermal distortion occurs in the negative feedback network, the distortion reduction effect due to the negative feedback effect cannot be obtained, causing deterioration of sound quality. In particular, if the current detection resistance is 0.1Ω, an amplification factor of 8 / 0.1 = 80 times is obtained with an 8 ohm speaker resistance, so a resistor that does not cause a problem of sound quality deterioration is required.

Regarding the first and second aspects, the thermal distortion from the resistor caused by the heat generated by the load current cannot be reduced and corrected because the resistor forms a negative feedback network. On the contrary, the present invention provides heat dissipation only by heat radiation and improves the heat retention effect, thereby improving thermal distortion and suppressing sound quality deterioration.

With respect to the third aspect of the present invention, the amount of heat generated by the resistor changes due to the flowing signal current, and the resistance value changes accordingly, causing thermal distortion. The purpose is to control the change in resistance value by radiating thermionic electrons by making the filament resistance of the vacuum tube red, and to improve the thermal strain by making the filament red as a resistor as a signal path. .

The resistor constituting the negative feedback network of the speaker current-driven negative feedback amplifier influences the sound quality of the negative feedback amplifier. Distortion caused by disturbance or heat generated by the resistance change due to heat generation. The correction by negative feedback is ineffective and causes a problem in sound quality.
In consideration of this point, in the speaker current drive amplifier, there is a problem in sound quality in the resistor that detects the current flowing through the speaker and applies negative feedback.
The present invention relates to a current detection resistor circuit used in a negative feedback circuit for solving this problem.

In the present invention, only the heat dissipated by heat radiation is applied, and ± bias voltage for heating is applied to make the bias voltage constant regardless of the presence or absence of a signal, thereby making the heat generation constant and improving the thermal distortion. Is.

The present invention devised the following means for solving the above-mentioned problems. A feature is provided in which one or a plurality of resistance elements are provided at a short distance where they can be thermally coupled to each other, and a bias voltage is applied to the resistance elements so that the resistance elements are red-heated to operate as signal processing resistors. It is a thermal distortion pre-sea resistance circuit.

The following means have been devised for solving the above-mentioned problems.
2. The thermal distortion improving resistor according to claim 1, wherein the resistance element of claim 1 is twisted and the thermal coupling is dense.

The present invention has devised the following means for solving the above-mentioned problems. In a vacuum tube amplifier circuit, a red-heated filament is used as a signal processing resistor, a change caused by passing a signal therethrough is detected, and the red-heated filament element is used as a resistor for applying a signal. This is a circuit for improving thermal distortion using a vacuum tube.

A negative feedback current drive amplifier for a speaker, which is a negative feedback resistor for detecting a current from the output section thereof, which is sealed in vacuum or gas, is red-heated, a signal current is passed, A speaker drive amplifier having a circuit function as a feedback resistor .

Describing claim 1 with reference to FIG. 1, the present invention provides the following effects.

(A) By causing a bias current to flow through the resistor element 6 and causing it to generate heat or red heat, the resistance value _RT of the resistor element 6 and resistor 7 is R _T = R ₀ (1 + αt) (1) Increase according to. Here, R ₀ is a resistance value at 0 ° C., _RT is a resistance value at t ° C., and α is a temperature coefficient of resistance. For example, referring to FIG.
In the case of a tungsten resistance element, if it is 6.6Ω (36) at 20 ° C., it becomes 100Ω (35) at 2,700 ° C. red heat, which is about 15 times the resistance value at 20 ° C., and is 6.6Ω. (36) to (38) are connected in series in 15 pieces and are equivalent to 100Ω. Therefore, the same material has high resistance, and the length of the length is reduced by 1/15, so that the factor of thermal disturbance is reduced and sound quality deterioration can be reduced. This has the effect of improving S / N.

(C) By applying a bias voltage for the purpose of generating heat, the average current flowing in the resistance element (6) and (7) is constant regardless of the magnitude of the input signal from the terminal (13), and thus the generated heat. Since the energy is also constant, the resistance values of the resistance elements (6) and (7) are constant and are not affected by thermal changes. If the input signal from the terminal (13) has a symmetrical waveform, the current due to the input signal flowing into the resistance element R (6) shown in FIG. 1 is + i (39) and -i (40) shown in FIG. Are the same. The average current i _AV (41) flowing into the resistance element R (6) does not change and is constant. Here, i _AV (41) is bias voltage E (10) / resistance element R (6). Since there is no change in the average current, even if the input signal changes, the average heat generation amount in the resistance element (6) does not change.
Therefore, the current consumption is the same when no signal is input and when there is no signal, so the amount of heat generation does not change and the resistance value of the resistance element (R6) does not change.
The same effect is obtained for the resistance element R (7). On the other hand, when no bias voltage is applied, there is no heat generation and the room temperature remains unchanged. When the input signal is applied at this non-bias voltage, the effective current i causes Q = Ki ² R (K: constant, R: R (6)) calorie thermal energy to be generated in the resistance element R (6). The heat generation temperature changes depending on the magnitude of the effective current i. Therefore, the resistance value of the resistance element R (6) changes according to the input signal from the relationship of R = βθ (R: resistance, β: constant θ: absolute temperature). Resulting in thermal distortion.
The same applies to the resistance element R (7). A bias voltage is applied for this effect. Even if the input signal changes, the average resistance value does not change, so that the thermal distortion is improved.

Referring to FIG. 5, (d) the resistance elements R ₁ (49) and R ₂ (50) are twisted to be close to each other, and the thermal coupling is made dense, whereby the resistance element R shown in FIG. ₁ (49) and R ₂ (50) have a function of reducing the mutual temperature difference when a bias voltage is applied and red-heated. As a result, the resistance elements R ₁ (49) and R ₂ (50) exhibit the same resistance value, and there is an effect of improving thermal distortion including stabilization of the point b (51).
As shown in FIG. 4, at the point d (45), the + R ₁ (46) side is in the + ip (47) increasing direction, and the -R ₂ (44) side is in the -ip (48) decreasing direction. specifically the coupling becomes thermally equal _R 1 = _{R 2} always by a dense, b point in Fig. 5 (51) keeps the zero v, the resistance element _R 1 (49) and the _R 2 ( 50) is also stable and has an effect of improving thermal distortion.

(E) By applying the same voltage with different positive and negative polarities as the bias voltage shown in FIG. 5, the amount of heat generated by the input signal current at the resistance elements R ₁ (49) and R ₂ (50) does not change, and therefore There is no change in resistance value, which is an effect of improving thermal distortion.
The bias voltage shown in FIG. 5 is applied with + Ev between a (49) and b (51) and -Ev between c (50) and b (51). If the input signal is Asinωt (52), the voltage applied to the resistance element R ₁ (49) is (+ Ev + Asinωt), and the voltage applied to the resistor R ₂ (50) is (−Ev + Asinωt). Therefore, the voltage E _T between a (49) -c (50) = (voltage between a−b) − (voltage between c−b) = (+ Ev + Asinωt − (− Ev + Asinωt) = + 2Ev, and the point b (51) is the center. Therefore, the input signal voltage Asinωt (52) becomes irrelevant to heat generation, and the thermal distortion is improved.

（Ｋ′，Ｋ″：定数）となる。従って定電圧電源をもってバイアス電圧Ｖを一定とすれば、（３）式より入力信号電圧に無関係に赤熱による絶対温度も一定となるので前記抵抗素子Ｒ（６）と同Ｒ（７）は一定となり熱的歪改善の効果が得られる。本発明は熱放射による放散熱のみとし、かつ赤熱のためのバイアス電圧を加えることで、入力信号の有無にかかわらず発熱を一定にし、熱的歪改善をはかるものである。(F) Generally, heat from resistance is lost as heat dissipated by conduction, convection, and thermal radiation. By placing the resistance elements R (6) and R (7) (FIG. 1) according to the present invention in a vacuum or gas, the red heat energy is lost solely by thermal radiation.
The heat dissipated by conduction and convection is larger than that by heat radiation. Therefore, even if this irregular and complicated fluctuation due to conduction and convection is very small, it can cause thermal strain sensitively. Here, since the heat dissipated by the resistance elements R (6) and R (7) is only thermal radiation, there is no influence by conduction and convection, and the thermal distortion is improved. The infrared as an electromagnetic wave is red hot the same R (7) and said added bias voltage resistance element R (6), the light, but emit thermal energy theta _T as ultraviolet light or heat electrons which Q _{T =} Kθ ^{4 _(θ} : Absolute temperature, K: constant). On the other hand, exothermic energy = V ² / R (V: voltage, R: resistance), this resistance R = βθ (β: constant), and red heat energy == heat radiation energy (at equilibrium), Q _T = V ² / R = Kθ ⁴ = K (R / β) ⁴

Therefore, if the bias voltage V is made constant with a constant voltage power source, the absolute temperature due to red heat becomes constant regardless of the input signal voltage from the equation (3), so that the resistance element R R (7) is the same as (6) and the effect of improving thermal distortion is obtained.In the present invention, only the heat dissipated by thermal radiation is applied, and the bias voltage for red heat is added, so that the presence or absence of the input signal is detected. Regardless, heat generation is kept constant and thermal distortion is improved.

(G) With respect to claim 3, the effect will be described with reference to FIG. 2. The filament is sealed in a vacuum inside the vacuum tube, and there is no heat dissipated by conduction and convection from the red hot filament. The effect of high thermal disturbance noise is suppressed. The red-heated filament resistance element (21) and (22) have the same effect as shown in the first aspect.

(H) A voltage change due to a signal in the resistance element (21) and (22) is detected as a signal directly from the plate (20) of the vacuum tube (19) as a voltage change between the grid (18) and the cathode (25). Then, this change is made to operate as a vacuum tube amplifier, and it becomes a vacuum tube filament resistance circuit integrated as a vacuum tube with a stable and good S / N, and a thermal distortion improving resistance circuit. (B) By applying the same bias voltage of different polarity to the red-heated resistance element, the voltage of the resistance in the middle becomes 0 volts, and the connected load is not affected by the voltage.

(N) The effect of claim 4 will be described with reference to FIG. 1. The resistance constituting the negative feedback network is one of the criteria for determining the sound quality. Thermal distortion and disturbance noise generated here are negative feedback. It is not improved by the operation, but is amplified and output as it is.
By using a thermal distortion improving resistor (12) or a vacuum tube resistance circuit (34) (shown in FIG. 2) according to the present invention as the current detection resistor for negative feedback, it is shown by claim 1 or claim 2 and claim 3. It becomes a speaker current drive amplifier characterized by the effect. The thermal distortion improving effect shown here includes the above (a), (b) (c), (d), (e) (f) (g) (g).
By this operation, the speaker is driven by current, and the resistor elements (6) and (7) as current detection resistors are always used in a state of being heated or red hot by a bias current. The vacuum tube resistance circuit (34) according to the second aspect also functions as a negative feedback resistor of a speaker current drive negative feedback amplifier as a similar current detection resistor.

Is an operation principle diagram according to the present invention. Is the resistance diagram of the vacuum tube Is an illustration of red heat resistance Is an explanatory diagram of a bias voltage waveform Is a twisted red heat resistance circuit explanatory diagram Is an external view of a thermal strain improving resistor

抵抗として負帰還回路を構成する。これはＲ＝Ｒとし、この端子（１３）と同（１４）の間が熱的歪改善抵抗値となる。The present invention relates to improvement of thermal distortion of a resistor used in a negative feedback circuit. In order to suppress the distortion due to heat generation, the conventional resistance suppresses the temperature rise caused thereby and reduces the thermal distortion. The present invention eliminates the heat dissipated by heat conduction and convection with respect to the heat generation of the resistance, maintains high heat, reduces the resistance value change due to the signal current flowing through the resistance by applying a bias voltage, and improves sound quality degradation. . The first and second aspects will be described with reference to FIG. 6. A resistor (55) including resistance elements R ₃ (53) and R ₄ (54) is shown. As shown in FIG. 6, the resistance elements R ₃ (53) and R ₄ (54) are sealed in an inert gas such as vacuum or argon, and the resistor (55) is vapor-deposited with silver or the like, and infrared, light, ultraviolet, etc. The heat transfer is suppressed by reflecting the electromagnetic wave and keeping the heat high. Light and infrared do not leak outside.
The resistor elements R ₃ (53) and R ₄ (54) are close to each other and have a close thermal coupling. Referring to FIG. 1, claim 1 will be described with reference to the ground point (14) as a reference from the power supply circuit (10) having the same polarity as + Ev and (11) to −Ev as the resistance element R (6) and R ( 7) is connected in series through terminals (8) and (9), and a bias voltage is applied to this to make it glow red.
The resistance elements R (6) and R (7) are connected in series as viewed from the terminals (8) and (9) from the power supply circuit (10) and (11) having different polarities. With reference to the point (14), the signal connection terminal (13) is located in the middle and the potential is 0v. As a result, the output section of the amplifier (2) including the speaker (4) is heated by the resistance elements (6) and (7) without being affected by the bias voltage. This is a resistor element R (6) and R (7) connected in parallel between the speaker (4) and ground.

A negative feedback circuit is configured as a resistor. This is R = R, and the resistance value between the terminals (13) and (14) is the thermal distortion improving resistance value.

Referring to FIG. 2 with respect to claim 3, the circuit included inside (34) surrounded by a dotted line represents the vacuum tube resistance circuit of the present invention. The power supply circuit (27) and (28) are output voltage circuits having different polarities. The filament (22) and (21) of the vacuum tube are connected to the terminals (23) and (26) from there. Add plus Ev and minus Ev to earth. The filament (22) and (21) are connected in series when viewed from the terminal (23) and the terminal (26), and are red-hot by the electric current generated thereby.
The voltage of the terminal (24) is taken from the middle of the filament (22) and (21), and the resistance value of both filaments is the same, so the voltage of the terminal (24) is 0V with respect to the ground. . Accordingly, the resistance value between the terminal (24) and the ground is the resistance value between the terminal (23) and the terminal (24) and the parallel connection between the terminal (26) and the terminal (24). The value is halved to constitute a negative feedback resistor.
The resistance value is a value at the time of red heat.

By applying an electric current to the filament (21) and the (22) to make them red hot, a signal voltage between the grid (18) and the cathode (25) of the vacuum tube (19) is taken out from the load resistor (32), and signal processing is performed. The change is processed and output by the amplifier (31) . Also supplied to the filament power supply circuit (28) (27). In this case, an offset resistor (30) with a voltage level appropriately set in the power supply circuit (28) and (27) is sent.

With reference to FIG. 4, the speaker (4) is connected to the output terminal (3) of the speaker-driven negative feedback amplifier (2), and the other end is the terminal of the resistor (5) of claim 1. Connect to (13). The speaker current flows from the other end (13) to the ground through the resistance elements R ₁ (6) and R ₂ (7).
The negative feedback signal is fed back from the terminal (13) and enters the inverting input of the speaker drive negative feedback amplifier (2). The resistor elements R (6) and (7) are connected in series when viewed from the terminal (8) and the terminal (9), and therefore flow through the resistor elements R ₁ (6) and R ₂ (7). The current i = 2Ev / (R + R), which causes the resistor (5) to glow red.

となり、これが電流検出抵抗となり、負帰還抵抗となる。Since the terminal (13) is 0 V with respect to the ground, the current from the power supply circuit (10) and (11) does not flow through the speaker (4), and there is no influence of the bias voltage. Connect with the speaker (4)

This becomes a current detection resistor and a negative feedback resistor.

DESCRIPTION OF SYMBOLS 1 Input terminal 29 Amplifier 2 Power amplifier 30 Offset resistance 3 Output terminal 31 Signal processing amplifier 4 Speaker 32 Load resistance 5 Resistor 33 Power supply 6 Resistance element 34 Negative feedback resistance 7 Resistance element 35 100Ω
8 terminals 36 6.6Ω
9 terminals 37 6.6Ω
10 Power supply circuit 38 6.6Ω
11 Power supply circuit 39 + i
12 Thermal strain improving resistor 40-i
13 terminals 41 Average current i _AV
14 Ground point 42 Ground 15 Input terminal 43 R ₂ side 16 Amplifier 44 -R ₂
17 Speaker 45 d point 18 Grid 46 + R ₁
19 Vacuum tube 47 + ip
20 plates 48-ip
21 Filament resistance element 49 Resistance element R ₁
22 Filament resistance element 50 Resistance element R ₂
23 terminal 51 b point 24 terminal 52 Asinωt
25 terminal 53 resistance element R ₃
26 terminal 54 resistor element R ₄
27 Power supply circuit 55 Resistor 28 Power supply circuit 56 Vacuum

Claims (4)

One or more resistance elements are sealed in a vacuum or gas, and the resistance elements are provided at a close distance where they can be thermally coupled to each other, and a bias voltage is applied to the resistance elements to make them red hot, A thermal distortion improving resistor circuit characterized by having a function of operating as a signal processing resistor. 2. The thermal distortion improving resistor according to claim 1, wherein the resistance element of claim 1 is twisted and the thermal coupling is made dense. In a vacuum tube amplifier circuit, a red-heated filament is used as a signal processing resistor, a change caused by passing a signal therethrough is detected, and the red-heated filament element is used as a resistor for applying a signal. Thermal distortion improvement circuit using a vacuum tube. A negative feedback current drive amplifier for a speaker, which is a negative feedback resistor for detecting a current from the output section thereof, which is sealed in vacuum or gas, is red-heated, a signal current is passed, A speaker-driven amplifier having a circuit function as a feedback resistor .

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