JP2011171819

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DESCRIPTION JP2011171819
In a ribbon type microphone, a large current is prevented from flowing in a ribbon at the time of
insertion and removal of a cable connector connected to a phantom power source, thereby
preventing the ribbon from being damaged or loosened and preventing generation of abnormal
noise. . A ribbon microphone unit 10 includes a ribbon 16 disposed in a parallel magnetic field
formed by a magnet 14 and outputting a signal by receiving an acoustic wave and vibrating, and
a primary winding at both ends of the ribbon 16 A step-up transformer 30 for boosting a signal
output from the microphone unit 10 by being connected to both ends of the capacitor 31, and a
capacitor C1 for storing a temporary current that flows when the phantom power is connected
via the connector; And a photo relay that is activated by a temporary current flowing to the
capacitor C1 and shorts the secondary winding 32 of the step-up transformer 30. [Selected
figure] Figure 1
Ribbon type microphone
[0001]
The present invention relates to a ribbon type microphone, and in particular, it is devised to
reduce the problem that the ribbon is displaced by an instantaneously flowing current when a
microphone cable to which phantom power is supplied is connected by a connector. It is.
[0002]
A pair of rod-like magnets are arranged in parallel to form a parallel magnetic field between
them, and in this magnetic field, a conductive ribbon diaphragm (hereinafter simply referred to
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as "ribbon") that receives sound waves and vibrates is arranged. Ribbon type microphones are
known which convert the vibration of a ribbon magnetoelectrically and convert it into an audio
signal.
Ribbon-type microphones generate electricity when a conductor crosses a magnetic flux, so the
principle is the same as dynamic-type microphones, and when current flows through the ribbon,
the driving force is applied to the ribbon by the electromagnetic force of the current and
magnetic flux. It occurs and the ribbon moves.
[0003]
The type of microphone widely used in recent years is a condenser microphone. The condenser
type microphone is provided with a diaphragm and a fixed pole made of thin films disposed
opposite to each other, and in order to make the diaphragm and the fixed pole function as a
capacitor, DC power is supplied from the outside as phantom power supply. . The phantom
power supply is specified in EIAJRC-8162A, which is a global standard, and phantom power is
supplied by connecting a standardized microphone cable to the connector of the microphone,
and an audio signal is supplied through the microphone cable. It can be output.
[0004]
Thus, in the field where the microphone is used, a phantom power supply is generally used, and
the phantom power can be supplied from the microphone cable. Therefore, even if it is a ribbon
type microphone or dynamic type microphone which originally does not require a phantom
power source, a pulse current, ie, rush current flows at the moment when the cable connector is
connected to the microphone connector. The pulsed current flows through the ribbon and
instantaneously becomes a large current, so that an abnormal noise accompanied by impulsive
sound is generated from the connector portion which is the output end of the phantom power
supply, and noise is generated in the signal circuit.
[0005]
In addition, since the ribbon microphone unit has a weak output signal, the voltage is boosted by
a step-up transformer to be used as a microphone output. However, by having the step-up
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transformer, the pulse-like current flowing at the moment when the connectors are connected
causes a failure. That is, the pulsed current flows in the secondary winding of the step-up
transformer. Since the step-up transformer has a large winding ratio such as a winding ratio of
1:70, even if the current flowing through the secondary winding is a small current, the primary
winding has a secondary winding. A current of about 70 times that of the flowing current flows,
and a large current flows in the ribbon. As a result, a large electromagnetic force is generated in
the ribbon, and the ribbon is largely displaced to break the ribbon, or the ribbon extends even if
not broken. When the microphone connector and the cable connector are connected and in the
steady state, the current from the phantom power supply does not flow in the secondary winding
of the step-up transformer, and the ribbon returns to the normal position. Therefore, by devising
that current does not flow in the ribbon only when connecting the connectors or disconnecting
the connectors, it is possible to prevent problems such as generation of noise and breakage of
the ribbon.
[0006]
An example of using a phantom power supply in a ribbon microphone is described in Patent
Document 1. The invention described in Patent Document 1 is a microphone circuit capable of
supplying an external power supply such as a phantom power supply so that a microphone
output can be obtained even when the external power supply is not supplied, such as a ribbon
type microphone or a dynamic type microphone. It is applicable. However, as described below,
the problems to be solved are different between the invention described in Patent Document 1
and the present invention.
[0007]
JP, 2007-312260, A
[0008]
An object of the present invention is to prevent the aforementioned problems that occur in
ribbon microphones when using a phantom power supply.
That is, at the moment when the cable connector connected to the phantom power source is
connected to the microphone connector and at the moment when the connectors are
disconnected, a large current is prevented from flowing in the ribbon to prevent the generation
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of a large electromagnetic force in the ribbon. It is an object of the present invention to provide a
ribbon type microphone which can prevent breakage or relaxation and can prevent generation of
abnormal noise when inserting and removing connectors.
[0009]
According to the present invention, there is provided a ribbon type microphone unit comprising a
ribbon type diaphragm arranged in parallel magnetic fields formed by magnets and outputting
signals by receiving sound waves and vibrating, and both ends of the ribbon type diaphragm are
one. A step-up transformer for boosting a signal output from the microphone unit by being
connected to both ends of a winding, and a capacitor for storing a temporary current flowing
when a phantom power source is connected via a connector; And a photo relay that is activated
by the temporary current flowing through the capacitor to short the secondary winding of the
step-up transformer.
[0010]
The circuit further includes a discharge circuit that discharges the charge accumulated in the
capacitor when the connectors are disconnected, and is provided with a second photorelay
operated by the discharge current to short-circuit the secondary winding of the step-up
transformer. Better still.
[0011]
When a cable connector connected to a phantom power supply is connected to the connector on
the microphone side, a large current flows instantaneously.
The current charges the capacitor, and the charge current activates the photorelay to short the
secondary winding of the step-up transformer.
When the secondary winding of the step-up transformer is short-circuited, no current flows in
the secondary winding, and no current flows in the primary winding magnetically coupled to the
secondary winding. Also, since no current flows, no electromagnetic force is generated to
displace the ribbon diaphragm. Therefore, damage and relaxation of the ribbon diaphragm can
be prevented, and abnormal noise when connecting the connectors can also be prevented. The
circuit configuration is devised by utilizing the step-up transformer, which is considered to be
essential for a ribbon type microphone unit whose output signal is weak, so that the intended
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purpose can be achieved.
[0012]
If a discharge circuit is provided that discharges the charge accumulated in the capacitor when
the connectors are disconnected, and a second photorelay is provided which operates with this
discharge current and shorts the secondary winding of the step-up transformer, Even when the
connectors are disconnected, the ribbon diaphragm can be prevented from being damaged or
loosened, and abnormal noise can also be prevented.
[0013]
It is a longitudinal cross-sectional view and circuit diagram which show the Example of the
ribbon type microphone which concerns on this invention.
It is a front view of the unit part of the said ribbon type microphone.
[0014]
Hereinafter, embodiments of the ribbon microphone according to the present invention will be
described with reference to the drawings.
[0015]
In FIGS. 1 and 2, reference numeral 10 denotes a ribbon microphone unit.
The ribbon microphone unit 10 has a rectangular frame-shaped yoke 12, two pairs of permanent
magnets 14, a ribbon diaphragm (hereinafter referred to as "ribbon") 16 and the like as main
components. In FIG. 1 and FIG. 2, on both opposing inner sides of a frame-shaped yoke 12 which
is long in the vertical direction, two bar-shaped magnets 14 having a rectangular cross section
are fixed at a predetermined interval. A parallel magnetic field is formed between the pair of
magnets 14 by magnetizing the pair of magnets 14 in the width direction and in the same
direction.
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[0016]
The ribbon 16 is formed of a thin film of a conductive, light-weight material such as aluminum in
a ribbon shape, that is, in the form of a long strip in the longitudinal direction in the figure, and
terminal portions 161 at both ends in the length direction are fixed to the terminal plate 18. The
ribbon 16 has an appropriate gap between the magnets 14 on both sides so that it can vibrate in
response to the sound wave in the parallel magnetic field by receiving the sound wave, and an
appropriate tension is applied to both ends. Terminal portion 161 is fixed to the terminal plate
18. Also, in order to be able to receive and vibrate the sound wave, the ribbon 16 is formed into a
wave shape by alternately bending the vibrating portions excluding the terminal portions 161 at
both ends along a line at fixed intervals in the width direction.
[0017]
The terminal plate 18 has a conductive pattern formed on an insulating substrate, and the
substrate is fixed to the yoke 12 by an appropriate means such as screwing in a state where the
conductive pattern is insulated from the yoke 12. The respective terminal portions 161 of the
ribbon 16 are overlapped and disposed on the conductive pattern of the terminal plate 18 fixed
to the longitudinal direction both ends of the yoke 12, and the both ends of the ribbon 16 are
pulled to apply appropriate tension. The respective terminal portions 161 are pressed by the
pressing member 22 in the state. Each pressing member 22 is fixed to the yoke 12 by a set screw
20 screwed into the yoke 12. In this way, the terminal portions 161 at both ends of the ribbon
16 are respectively sandwiched between the conductive pattern of the terminal plate 18 and the
pressing member 22 and are conducted to the conductive pattern.
[0018]
When the ribbon 16 vibrates according to the acoustic wave, the conductive ribbon 16 crosses
the parallel magnetic field in the space in which the ribbon 16 is disposed, so that an electrical
signal is generated in the ribbon 16 by the principle of magnetoelectric conversion. This
electrical signal is a signal in accordance with the sound wave received by the ribbon 16, and in
this way is to be electroacoustically converted. The electrical signal can be extracted from the
conductive patterns of the terminal plates 18 at both ends.
[0019]
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The description so far is not different from the conventional ribbon microphone unit. The feature
of the present invention lies in the circuit configuration described below. When a conventional
ribbon microphone is connected to a connector connected to a phantom power supply, the
above-described problems occur. Therefore, in the illustrated embodiment, the circuit is devised
to prevent such problems.
[0020]
In FIG. 1, the conductive patterns of the terminal plates 18 at both ends are respectively
connected to the ends of the primary winding 31 of the step-up transformer 30. Therefore, each
terminal portion 161 of the ribbon 16 is connected to each end of the primary winding 31. The
winding ratio of the step-up transformer 30 is, for example, as high as 1:70. The secondary
winding 32 of the step-up transformer 30 is provided with a center tap. An output signal of the
ribbon microphone unit 10 is connected to be balanced output through a standardized 3-pin
connector, and a phantom power supply is connected to the 3-pin connector. In FIG. 1, circled
numbers 1, 2 and 3 respectively indicate the numbers of connector pins, and each pin is
connected to a two-core signal line and a shield line surrounding the periphery of these signal
lines. The first pin is a pin connected to the ground and connected to the shield wire. The second
pin is connected to the signal line on the hot side, and the third pin is connected to the signal line
on the cold side for balanced output.
[0021]
The second pin of the connector is connected to one end of the secondary winding 32 of the
step-up transformer 30, and the third pin of the connector is connected to the other end of the
secondary winding 32 of the step-up transformer 30. A series circuit of a constant current diode
D1, a light emitting element LED1 and a capacitor C1 is connected between the center tap of the
secondary winding 32 and the first pin of the connector. This series circuit constitutes a charging
circuit for charging the capacitor C1 with the current temporarily flowing from the phantom
power supply when the cable connector is connected to the connector of the above 3-pin
configuration. The temporarily flowing current includes a current flowing from the pin 2 side and
a current flowing from the pin 3 side. In any case, these inflow currents flow from the center tap
of the secondary winding 32 of the step-up transformer 30 through the constant current diode
D1, the light emitting element LED1 and the capacitor C1 to charge the capacitor C1. The
constant current diode D1 connected to the charging circuit for the capacitor C1 is selected to
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have a relatively high AC impedance. The light emitting element LED1 emits light by the charging
current.
[0022]
A resistor R2 is connected between the second pin of the connector, that is, one end of the
secondary winding 32 of the step-up transformer 30, and the ground, and a resistor R1 is
connected between the other end of the secondary winding 32 and the ground. It is connected.
An open / close switch SW1 is connected between the second and third pins of the connector,
and thus between both ends of the secondary winding 32. Although FIG. 1 depicts the on / off
switch SW1 as if it is a mechanical on / off switch, the switch SW1 is an active element that is
combined with the light emitting element LED1 to constitute a photo relay. When the light
emitting element LED1 emits light by energizing the light emitting element LED1, the light is
received by the switch SW1 and the both ends of the secondary winding 32 of the step-up
transformer 30 are shorted.
[0023]
The emitter of a PNP transistor Q1 is connected between the light emitting element LED1 and the
capacitor C1. The base of the transistor Q1 is connected between the constant current diode D1
and the light emitting element LED1 via the diode D3. Thus, a discharge circuit of the capacitor
C1 including the capacitor C1, the emitter and base of the transistor Q1, the diode D3, the
constant current diode D1, the secondary winding 32 of the step-up transformer 30, the resistor
R1 or the resistor R2 is configured. . The discharge circuit is formed when the connection
between the 3-pin connector and the cable connector is broken. The formation of the discharge
circuit turns on between the emitter and the collector of the transistor Q1, and turns on the
transistor Q1 to form a discharge circuit consisting of the capacitor C1, the emitter and the
collector of the transistor Q1, the light emitting element LED2 and the constant current diode D2.
And connected so that a discharge current flows from the capacitor C1.
[0024]
The light emitting element LED2 emits light by the discharge current of the capacitor C1. The
light emitting element LED2 constitutes a second photo relay together with the open / close
switch SW2. The switch SW2 is connected between pins 2 and 3 of the connector, and thus
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across the secondary winding 32. Although FIG. 1 depicts the on / off switch SW2 as if it is a
mechanical on / off switch, the switch SW2 is an active element that is combined with the light
emitting element LED2 to constitute a photo relay. When the light emitting element LED2 emits
light by energizing the light emitting element LED2, the light is received by the switch SW2 and
the both ends of the secondary winding 32 of the step-up transformer 30 are shorted.
[0025]
Next, the operation of the above embodiment will be described. First, an operation when the
cable connector is coupled to the connector on the microphone side will be described. When the
above-mentioned connectors are coupled while the phantom power is connected to the cable
connector, at the moment, the current I1 flows from the phantom power connected to the 2nd
and 3rd pins of the connector to the capacitor C1, and the capacitor C1 is charged Be done. The
charging circuit of the capacitor C1 is a circuit comprising the second pin of the connector, the
half of the secondary winding 32 of the step-up transformer 30, its center tap, the constant
current diode D1, the light emitting element LED1 and the capacitor C1, and the third of the
connector. There are two circuits: a terminal, the other half of the secondary winding 32 of the
step-up transformer 30, its center tap, a constant current diode D1, a light emitting element
LED1, and a capacitor C1. In FIG. 1, these charging circuits are indicated by solid arrows.
[0026]
The charging current I1 flowing to the capacitor C1 is controlled to a constant current by the
constant current diode D1, and the light emitting element LED1 emits light by this current. The
light is received by the switching element SW1 which forms a photo relay together with the light
emitting element LED1 and turned on, thereby shorting the secondary winding 32 of the step-up
transformer 30. Since the secondary winding 32 of the step-up transformer 30 is magnetically
coupled to the primary winding 31, the shorting of the secondary winding 32 is the same as the
shorting of the primary winding 31, Thus, the electromagnetic braking force acts on the ribbon
16 in the same manner as when both ends of the ribbon 16 are shorted.
[0027]
As described above, the winding ratio of the step-up transformer 30 is a fairly high winding ratio
such as 1:70. The impedance on the side of the secondary winding 32 is determined by the
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contact resistance or internal resistance of the switching element SW1. On the other hand, the
impedance of the primary winding 31 is obtained by multiplying the impedance of the secondary
winding 32 by the square of the winding ratio. Therefore, in the ribbon type microphone using
the step-up transformer 30 having a large winding ratio as described above, when the secondary
winding 32 of the step-up transformer 30 is short-circuited, the resistance value is as close to
zero as possible. The ends of the ribbon 16 will be short-circuited by the wire 31, and the
electromagnetic braking force effectively acts on the ribbon 16.
[0028]
In this way, even if the cable side connector is coupled to the connector on the microphone side
and current instantaneously flows from the phantom power source, this current flows to the
capacitor C1 and charges are accumulated, and the above-mentioned instantaneous current Since
the both ends of the ribbon 16 are short-circuited via the secondary winding 32 and the primary
winding 31 of the step-up transformer 30 through the photorelay while flowing, the generation
of the above-mentioned instantaneous current and the electromagnetic force by the ribbon 16
Can be prevented. Thus, it is possible to prevent the ribbon 16 from being broken or loosened by
the electromagnetic force, and it is also possible to prevent the ribbon 16 from generating noise.
When the charging current to the capacitor C1 does not flow, the photorelay returns to the
original state, the ribbon microphone unit 10 performs normal electroacoustic conversion
operation, and the step-up transformer 30 also performs normal boost operation.
[0029]
Next, the operation when the connector on the microphone side and the cable connector are
disconnected will be described. Also when disconnecting the connector, if it is assumed that the
phantom power is still connected to the cable connector, a pulse current flows instantaneously.
According to the conventional microphone circuit, the above-mentioned failure has occurred due
to this pulsed current. According to the illustrated embodiment, when the connectors are
disconnected, the charge stored in the capacitor C1 is discharged, and the photorelay is operated
by this discharge current to make the secondary winding of the step-up transformer 30 By shortcircuiting and short-circuiting the ribbon 16, occurrence of a failure can be prevented. More
specifically, when the connectors are disconnected and the supply of phantom power is stopped,
the charge stored in the capacitor C1 is a discharge circuit indicated by an alternate long and
short dash line in FIG. 1, that is, the emitter and base of the transistor Q1. A discharge circuit is
formed, which includes the diode D3, the constant current diode D1, the secondary winding 32 of
the step-up transformer 30, and the resistors R1 and R2. The transistor 12 is turned on by the
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current I2 flowing through the discharge circuit, and the discharge current of the capacitor C1
flows via the emitter and the collector of the transistor Q1, the second light emitting element
LED2 and the constant current diode D2. This discharge circuit is indicated by a two-dot chain
line in FIG.
[0030]
The light emitting element LED2 is turned on by the discharge current I3, and the second
switching element SW2 which constitutes the second photo relay together with the light emitting
element LED2 receives the light from the light emitting element LED2 and is turned on. The
turning on of the switching element SW2 is the same as the turning on of the switching element
SW1. As a result, the both ends of the ribbon 16 are short-circuited, and the electromagnetic
braking force acts on the ribbon 16. . As a result, the generation of the above-mentioned
instantaneous current and the generation of the electromagnetic force by the ribbon 16 can be
prevented, and the ribbon 16 can be prevented from being damaged or relaxed by the
electromagnetic force, and abnormal noise is generated from the ribbon 16 Can also be
prevented. When the charge stored in the capacitor C1 is discharged, the switching element SW2
that constitutes the photorelay together with the light emitting element LED2 returns to the off
state.
[0031]
When inserting or removing the microphone cable connected to the phantom power supply,
turning off the phantom power supply is the correct handling to avoid damaging the microphone.
However, there is a possibility that the connector is inserted and removed while the phantom
power is on without knowing or knowingly. According to the present invention, even if the
connector is removed without disconnecting the phantom power source, the microphone is not
damaged, so that the user-friendly microphone can be provided.
[0032]
DESCRIPTION OF SYMBOLS 10 ribbon type microphone unit 12 yoke 14 magnet 16 ribbon type
diaphragm 30 step-up transformer 31 primary winding 32 secondary winding C1 capacitor
LED1 light emitting element LED2 second light emitting element SW1 switching element SW2
second switching element
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