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Specification 1, Title of the invention Equalizer amplifier RIAA A changeover switch for
selectively connecting the non-inverted input terminal and the inverted input terminal of the
amplifier connected to the negative feedback circuit for the reproduction curve is provided. An
equalizer amplifier characterized in that the amplifier is used as a non-inverting amplifier in the
case of using a cartridge, and the amplifier is used as an inverting amplifier in the case of using a
moving coil 'fJ cartridge.
2, the scope of claims
The present invention relates to an equalizer amplifier, and more specifically, a special stepping
transformer or a dedicated amplifier may not be used (a moving magnet using an amplifier
having a RIAA equalizer characteristic, a five-ping coil cartridge The equalizer amplifier which
can be used for both of The moving coil type cartridge has a small mass at the vibration part and
can be taken large compliance, so it has excellent trackability of the record groove, the vibration
system is one end supported type, and the problem is that the vibration mode is simple and
theoretical 1 (a) K, the cartridge terminal CT and RIAA equalizer characteristics are moved as
shown in FIG. 1 (a) K because the output voltage is low, as it is easy to make the glu close to 15
°. A step-up transformer SUT is provided between the magnet type cartridge amplifier MMA by
means of a switch 81.81 'for selectively connecting the transformer to the input of the moving
magnet type cartridge amplifier MMA to obtain sensitivity, or Fig. 1 (B) As shown by K, a
cartridge terminal CT and a mute having RIAA equalizer characteristics A dedicated amplifier
MCA is provided between the amplifier MMA and the ring magnet type cartridge amplifier by
selectively connecting the amplifier to the input of the moving magnet type matrix amplifier
MMA with the switch B1 ° Sl 'to obtain one sensitivity. It was used. : When using the former
step-up transformer, EndPage: 1 is limited in the power supply induction hum or the frequency
characteristics and distortion peculiar to the transformer, and it becomes expensive, and the
circuit configuration when the latter dedicated amplifier is used It wasn't good that it was too
expensive. SUMMARY OF THE INVENTION The present invention aims to solve the abovementioned conventional drawbacks in the use of a moving coil type cartridge, and its feature is
that the RIAA equalizer characteristic is converted to an inverting amplifier or a non-inverting
amplifier. By using it as an inverting amplifier, it is used in common to both cartridges as an
output amplifier matched to a shim-bin coil type and moving magnet type cartridge. The present
invention will be described in detail with reference to an embodiment shown in the drawings.
FIG. 2 is a block diagram of a moving coil type moving magnet type cartridge equalizer according
to the present invention. This is a positive input terminal (non-inverting input terminal) INI of the
differential input type operational amplifier OPA. And the negative input terminal (inverted input
terminal) IN2 are connected to the movable contacts c and e 'of the changeover switch 5IISI'
while the resistor Rg is interposed between the positive input terminal INI and the ground
terminal E, and the negative input terminal IN2 and the ground terminal A resistor RE is
connected between E and E, and a negative feedback circuit element Zf for RIAA regeneration
curve is connected between the output terminal OUT and the negative input terminal IN2, and
the changeover switch 81.
The fixed contacts a and b 'of Sl' are connected to the cartridge terminal CT, and the fixed contact
of the changeover switch S1 is connected to the ground terminal E, respectively. Next, the
operation of this equalizer amplifier will be described with reference to FIGS. 6 and 4. As shown
in FIG. 6, the changeover switch S1. When the movable contacts e and e 'of S1' are connected to
the fixed contacts a and a ', respectively, the input impedance is high and matching is performed
on the moving magnet type cartridge, which is equivalent to the conventional equalizer amplifier
(for moving magnet type). The circuit configuration is advantageous for easy-to-use inductive
signal sources. In this case, the signal from the signal source e8 + Rs flows in a loop passing
through the transistors Q1 and Q2 forming the first stage differential amplifier of the amplifier
OPA and the resistor RE, and the transfer characteristic G in this case is c == 1 + Zf1, A reference
characteristic is obtained by using a RIAA regenerative curve element as the feedback circuit Zf.
Next, as shown in FIG. 4, the movable contacts e and e 'of the changeover switch 81.81' are fixed
contacts, and when they are connected to b ', the positive input terminal! N1 is connected to the
ground terminal E, and the cartridge terminal CT is connected to the negative input terminal IN2.
In this case, it becomes an inverting amplifier, so the signals from the signal sources es and Rs
are transistors constituting the first stage differential amplifier of the amplifier OPA It flows in a
loop that passes only Ql and Q2, and in this case the transfer characteristic G, =-is -elRs / RE and
fkj! 7. A circuit configuration suitable for a moving coil type cartridge. That is, the moving coil
type cartridge ′ has a low internal resistance (several Ω to several hundreds), is almost pure
resistive in the audio band, and has very few inductive elements such as the moving magnet type,
and thus such a current drive type It doesn't matter if you configure it. Further, since the signal
loop internal pressure resistance RE is not included, the noise as a whole is reduced by the noise
generation amount in the resistance RE as compared with the non-inverting amplifier in FIG.
Moreover, since the moving coil type cartridge has a relatively proportional relationship between
the internal resistance and the output voltage, when the current drive is performed, the change in
the output signal eo due to the variation of the cartridge output voltage is reduced, and the
sensitivity switching etc. due to that is practically unnecessary. It is versatile. FIG. 5 shows an
example in which the present invention is applied to an amplifier other than a differential
amplifier, in which the cartridge terminal CT is connected to the fixed contacts a and b 'of the
interlock switch D1, S1 / and the other fixed contacts are connected. Do not connect any fixed
contact a 'to ground and move contact C'!
In addition, the movable contact C is connected to the base of the transistor EndPage: 2 star Q1
and grounded via the resistor Rg, and the base is further connected to the emitter of the
transistor Q2 via the resistor R2. The emitter is grounded via resistor R4. トランジスタQ1のコ
レクタをトランジスタ。 2. Connected to the base of 2 and connected to the power supply VccK
via a resistor R1 and connected the collector of the transistor Q2 to the power supply Vce via a
resistor R3, and the same transistor. The collector of No. 2 is connected to the output terminal
OUT, and the output terminal OUT is connected to the emitter of the transistor Q1 via the
negative feedback circuit element Zf, and the emitter is grounded via the resistor RE to move the
movable contact C of the changeover switch 81 '. It is connected to '. The operation in this case
can be switched to the moving coil type or moving magnet type cartridge as in FIGS. 2 to 4
described above. As described above, the present invention connects 21 negative feedback
circuits for RIAA regeneration curve, and has 21 input terminals (a non-inverting input terminal
and a reverse input terminal are provided with a changeover switch serving as a noninverting
input terminal). In the case of using a cartridge, the amplifier is changed to a non-inverted
amplifier, and in the case of using a moving coil type car) IJ flange, the above-mentioned amp
and the switch are changed so as to sufficiently exhibit the characteristics of both cartridges.
Therefore, the step-up transformer and the moving coil type cartridge dedicated amplifier
required when using a moving coil type cartridge are not required, and one RIAA amplifier can
be used in common, and the circuit configuration is simple. The impedance on the terminal side
is directly connected to the input terminal, so It is source has the effect of such a circuit
configuration suitable only internal elements of the operational amplifier determines the noise is
small sheet, and both the cartridge.
4. Brief description of the drawings FIGS. 1 (a) and 1 (b) show the structure of a conventional
equalizer amplifier), and FIGS. 2 to 4 each show an embodiment of the present invention, FIG. 2 is
a block diagram of an equalizer amplifier, FIGS. 3 and 4 are diagrams for explaining two
operations of the equalizer amplifier, and FIG. 5 is a block diagram composed of amplifiers other
than differential amplifiers. CT: Cartridge terminal, oPA channel application, Sl, Sl ': Change-over
switch, Rg, RE: Resistance, zf: Negative feedback circuit element, oUT: Output terminal, E ..・
Earth terminal. Patent Assignee Nippon Musical Instruments Manufacturing Co., Ltd. Agent
Fudan Rokubu Denki-same month 2 2nd 1st (0-) Fig. 1 (() EndPage: 3
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description, jps5378801
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