JPS6211047Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an amplifier that amplifies the output signal of a transducer, and particularly relates to an amplifier that extracts the output signal without deteriorating it in the signal path and equalizes the same signal. .

Generally, in the output reproducing device of a transducer (pickup cartridge of a player, head of a tape recorder, etc.), the minute output signal of the transducer is guided to an amplifier via various lead wires and connectors, so that the signal is There is a problem of deterioration in the signal path made up of the lead wires and the like. For example, in a signal reproduction system that uses a moving coil pickup cartridge as a signal source, the output level obtained from the signal source is extremely low, so this is first amplified by a head amplifier, and this amplified output is supplied to the pre-main amplifier. In the signal path in this case, the head amplifier is usually installed inside the case of the player or inside the pre-main amplifier.
The lead wires used to guide the minute signals from the pick-up cartridge to the head amplifier become long, and there is a problem in that the signal quality (frequency characteristics, SN ratio, etc.) deteriorates in these lead wires and the connectors used to connect them. . That is, the conductors such as lead wires and connectors constituting the signal path constitute DC resistance R, inductance L, and capacitance C depending on their material, structure, connection state, structure of the contained object, etc. Nonlinearity is formed at the joint (the oxide film that forms on the surface of the metal conductor forms nonlinearity near zero in the voltage-current characteristics, affecting minute signals), and these This may cause quality deterioration. Although this problem can be improved by simplifying the signal path, the reality is that this is usually not possible due to constraints on the equipment configuration.

In addition, in the case of a transducer output reproducing device, for example, if this is a recording equalizer signal reproducing device, the amplifier must be configured as an equalizer amplifier in order to reproduce and equalize the output signal of the transducer. Conventional equalizer amplifiers have problems in that the output signal of the amplifier deteriorates and problems in the structure of the amplifier itself. That is, a conventionally commonly used equalizer amplifier will be explained with reference to FIG _. 1. Figure a shows a CR type equalizer amplifier, in _which resistors R ₁ , R ₂ , An equalizer circuit consisting of R ₃ and capacitors C ₁ and C ₂ is inserted. In this CR type equalizer amplifier, equalizer characteristics can be obtained accurately and relatively good sound quality characteristics can be obtained, but on the other hand, the utilization rate of the amplifier output is low and the circuit configuration is complicated. Also, b in the same figure
This shows an NF type equalizer amplifier, in which the operational amplifier A ₃ is configured as a non-inverting amplifier, and its feedback circuit is configured with equalizer elements (resistors R ₄ , R ₅ , R ₆ , capacitors C ₃ , C ₄ ). . this
In the NF type equalizer amplifier, the utilization rate of the amplifier output is high and the circuit configuration is simplified, but on the other hand, the high frequency part of the equalizer characteristics deviates from the ideal characteristics, and the sound quality characteristics are generally lower than the above-mentioned CR type. There is a disadvantage that it is inferior. Also, c and d in the same figure are CR/NF
This figure shows a hybrid equalizer amplifier. Figure c shows the feedback circuit of operational amplifier _A3 consisting of equalizer elements (resistors R ₇ , R ₈ , R ₉ , capacitor C ₅ ), and the output circuit including an equalizer element (resistor R ₁₀ , capacitor C ₆ ), and Figure d shows an equalizer element (resistance R ₁₁ , capacitor C ₇ ) inserted in the input circuit of operational amplifier A ₃ , and a feedback circuit connected to the equalizer element (resistance R ₁₂ , R ₁₃ R ₁₄ , and a capacitor C ₈ ). Although these hybrid equalizer amplifiers improve the equalizer characteristics and the utilization rate of the amplifier output, they have the disadvantage that the circuit configuration is extremely complicated.

As described above, in conventional transducer output reproducing devices, there is a problem that the output signal of the transducer deteriorates in the signal path, and when equalizing the output signal,
The equalizer amplifier used in this case had various problems.

In view of the above circumstances, this invention allows the output signal of the transducer to be taken out without deteriorating in the signal path, and also enables accurate reproduction equalization without causing a decrease in the utilization rate of the amplifier output. , and provides an amplifier with a simple circuit configuration, consisting of a field effect transistor placed near a transducer and to which the output voltage of the transducer is applied between the gate and source, and the drain of this field effect transistor. and a first and second output extraction system connected to the source, a transistor whose emitter is connected to the other end of the first output extraction system, and the other end of the second output extraction system. and a constant voltage circuit that maintains a constant voltage between the bases of the transistor, a load of a CR type equalizer circuit inserted between the collector of the transistor and the power supply terminal, and a load of a CR type equalizer circuit inserted between the collector of the transistor and the output terminal. It consists of a capacitor and a capacitor.

An embodiment of this invention is shown below in Figures 2 to 3.
This will be explained with reference to the figures.

In this embodiment, this invention is applied to a player playback system, and FIG. 2 shows the wiring state of the system. In the figure, 1 is a player;
2 is the case of player 1, 3 is the turntable,
4 is a pickup cartridge, 5 is a head shell, 6 is a tone arm, and 7 is an external adapter. The output terminal 8 of the head shell 5 is connected to the player output terminal 10 via a lead wire 9 passing through the tone arm 6.
It is connected to the input terminal 12 of the external adapter 7 by. The signal path from the pick-up cartridge 4 to the adapter 7 shown in FIG. 2 constitutes the circuit shown in FIG. 3. That is, in FIG. 3, the generator coil 13 of the pick-up cartridge 4 is connected to one output terminal 13
A is connected to the gate of the field effect transistor _Q1 , and the other output terminal 13b is connected to the source of the field effect transistor _Q1 . The field effect transistor Q ₁ amplifies the voltage generated in the power generating coil 13 and converts it into a current. It is connected to one output terminal 8a, and its source is connected to the other output terminal 8b. The output terminal 8a is connected to the player output terminal 10a by a lead wire 9a, and the output terminal 8b is connected to the player output terminal 10b by a lead wire 9b. Further, the output terminal 10a is connected to the input terminal 12a of the adapter 7 by one connection cord 11a.
The output terminal 10b is connected to the same input terminal 12b by the other connection cord 11b. The above lead wires 9a, 9b and connection cords 11a, 11b serve as a power supply path to the field effect transistor _Q1 as well as an output extraction path of the field effect transistor _Q1 , as will be described later. . In addition, in the adapter 7, the input terminal 12a is connected to the emitter of the transistor _Q2 , and the input terminal 12b is connected to the output terminal (ground terminal) 1.
4b. Transistor Q ₂ along with its bias circuit connects field effect transistor Q ₁
constitutes a constant voltage supply circuit that supplies a constant power supply voltage between the drain and source of the circuit, and its collector is connected to the positive power supply terminal 16 via a load 15 and to the output terminal 14a via a capacitor 17. The base thereof is connected to the positive power supply terminal 16 via a constant current circuit 18, and is also connected to the output terminal 14b via a resistor 19. Further, a resistor 20 is inserted between the output terminals 14a and 14b. The load 15 is composed of resistors 21 and 22 inserted in series between the collector of the transistor Q ₂ and the positive power supply terminal 16, and capacitors 23 and 24 connected in parallel to the resistors 21 and 22, respectively. resistors 21, 22 and capacitor 2
3 and 24 function as a so-called CR type equalizer circuit, and the outputs obtained at the output terminals 14a and 14b are equalized. In this embodiment, the time constants of each element are set as follows so that the equalizer curve corresponds to the RIAA reproduction curve. That is, when the values of the resistors 21 and 22 are respectively r ₂₁ and r ₂₂ and the values of the capacitors 23 and 24 are C ₂₂ and C ₂₄ respectively, the high frequency time constant is T _H
= C ₂₃ , r ₂₁ = 75 [μsec], the low frequency time constant is T _L =
C ₂₄ , r ₂₂ = 3180 [μsec], the time constant in the middle range is T _M =
C ₂₄ , (C ₂₃ + C ₂₄ ) (r ₂₂ r ₂₁ ) = 318 [μsec].

Next, to explain the operation of the above circuit, in FIG. 3, a constant current circuit 18 and a resistor 19 are applied with a constant bias to the base of the transistor _Q2 , so that the input terminals 12a,
A constant voltage is obtained between the transistors 12b and 12b, and this voltage is applied between the drain and source of the field effect transistor _Q1 via the connection cords 11a and 11b and the lead wires 9a and 9b. Field effect transistor Q ₁
Since its gate and source are short-circuited by the power generating coil 13 in a direct current manner, these are at the same potential, a constant current flows between the drain and the source, and the transistor is placed in an active state. When a voltage is induced in the generator coil 13, this voltage is applied between the gate and source of the field effect transistor _Q1 , and is amplified by the field effect transistor _Q1 . This amplified output is a field effect transistor
Lead wires 9a, 9 from between the drain and source of _Q1
b, is supplied to the adapter 7 side via connection cords 11a, 11b, changes the voltage across the load 15 to change the collector voltage of the transistor _Q2 , and from the collector via the capacitor 17 to the output terminals 14a, 14b. taken out in between. Therefore, in this circuit, the lead wires 9a, 9b,
_The connection cords 11a and _11b receive a signal (current _converted signal) will be supplied, and the same signal will be supplied to the DC resistance R, inductance L, and capacitance C created by the lead wires 9a and 9b and the connection cords 11a and 11b.
It is hardly affected by. Further, the signal current is superimposed on the power supply current (saturated drain current) of the field effect transistor Q ₁ and is passed through the lead wires 9a, 9b,
It will flow through the connection cords 11a and 11b,
Adverse effects from non-linearity caused by connectors inserted in this signal path are also prevented. That is, the field effect transistor Q ₁ flowing in the signal path
The saturated drain current is at a level that is not easily affected by nonlinearity created by connectors, and the signal current superimposed on this saturated drain current is not affected by the nonlinearity.

Further, since the load 15 has the RIAA regeneration curve, the output taken out between the output terminals 14a and 14b has the frequency characteristics of the same curve.
At this time, the utilization rate of the amplified output of the field effect transistor _Q1 does not decrease even though the load 15 is constituted by a CR type equalizer circuit.

In the above embodiment, the present invention was applied to a signal path of a player having a moving coil type pickup cartridge, but the present invention is applicable to signals of various transducers such as a playback head of a tape recorder. It may be a line.

As is clear from the above explanation, according to this invention, the signal voltage of a transducer such as a pick-up cartridge is converted into a current by a field effect transistor placed near the transducer and extracted. The signal to be extracted is not degraded by impedance created by lead wires, connection cords, etc. in the signal path, and when the signal passes through conductor joints such as connectors inserted in the signal path. Since this is passed under the bias of the power supply current supplied to the field effect transistor, it is not affected by the nonlinearity created by the conductor junction.

Also, the load can be configured with a capacitor and a resistor.
Since it is a CR type equalizer amplifier, the configuration is simple and the circuit can have an accurate reproduction equalizer curve. Furthermore, although it is a CR type equalizer amplifier, there is no reduction in the utilization rate of the amplifier output. In addition, even though it is an equalizer amplifier, it can be configured with a single amplification stage between the signal source and the output terminal, so the phase rotation that occurs when the signal passes through the amplification stage can be suppressed slightly, making it stable. You can get the desired behavior. Furthermore, since the circuit can be configured with a DC amplifier, the circuit does not have a DC time constant, and therefore the low frequency characteristics do not deteriorate. Furthermore, the gain and frequency characteristics of the circuit can be easily adjusted, and any transfer load function can be easily set.

[Brief explanation of the drawing]

Figures 1a, b, c, and d are circuit diagrams of equalizer amplifiers commonly used in the past, Figure 2 is a diagram showing the connection state of a player playback system to which this invention is applied, and Figure 3 is an amplifier according to this invention. FIG. 13... Generator coil, 9a, 11a... First output extraction system path, 9b, 11b... Second output extraction system path, 15... Load, 17... Capacitor, 1
8,19...constant voltage circuit, _Q1 ...field effect transistor, _Q2 ...transistor.

Claims (1)

[Scope of utility model registration request] A field effect transistor disposed near the transducer and to which the output voltage of the transducer is applied between the gate and source, and first and second output outputs connected to the drain and source of the field effect transistor, respectively. a transistor having an emitter connected to the other end of the first output extraction circuit; and a constant voltage circuit that maintains a constant voltage between the other end of the second output extraction circuit and the base of the transistor. , an amplifier comprising: a load having a CR type equalizer circuit configuration inserted between the collector of the transistor and the power supply terminal; and a capacitor inserted between the collector of the transistor and the output terminal.