JPH0319047Y2 - - Google Patents

Description

[Detailed description of the invention] This invention changes and varies the applied voltage of the bias oscillation circuit according to the type of tape used by switching the tape select switch, and finely adjusts the applied voltage using a variable resistor for fine adjustment to improve the sound quality. Regarding a tape recorder to be corrected, almost the same sound quality correction can be performed regardless of the type of tape used.

Conventionally, tapes used in tape recorders have various characteristics, such as normal tape, chrome tape, and metal tape, and the various tapes are provided by many manufacturers.

Even in the case of tapes of the same type, if they are made by different manufacturers, there will usually be several dB differences in frequency response and maximum recording level when using the same amount of recording bias. It is necessary to fine-tune the voltage applied to the bias oscillator circuit so that the same desired sound quality can be recorded on each manufacturer's tape.

Therefore, it is necessary to provide a bias fine adjustment circuit in the bias oscillation circuit, and the bias oscillation circuit of a conventional tape recorder is configured as shown in FIG.
By switching the two NPN oscillation transistors Q ₁ and Q ₂ that are push-pull connected to the primary side of the oscillation transformer T, a high frequency is generated on the secondary side of the transformer T, and the recording/reproducing head (not shown) and A recording bias and an erasing bias are respectively supplied to the erasing head H.

In Figure 1, C ₁ and C ₂ are capacitors for preventing separation deterioration, C ₃ is a resonant capacitor for determining the oscillation frequency, C ₄ , C ₅ , and C ₆ are capacitors for preventing abnormal oscillation, and C ₇ is the oscillation feedback amount. Determining capacitor, C ₈
is the power supply decoupling capacitor, _R1 is the emitter resistance of both transistors _Q1 and _Q2 , and _R2 is the bias resistance.

On the other hand, in order to control the applied voltage of the bias oscillation circuit, an NPN type power supply voltage control transistor is connected to the power supply terminal +B side of the primary side circuit of the bias oscillation circuit.
The emitter and collector of transistor Q ₃ are inserted in series, and the above-mentioned applied voltage is controlled by the voltage between the emitter and collector of transistor Q ₃ .

and the collector-emitter of transistor _Q3 ,
Since the voltage between them is controlled by the base current, a resistor R for determining the lower limit of bias fine adjustment is connected between the recording contact r of the recording/reproducing switch _S1 , which has a recording contact r and a playback contact p, and the collector of the transistor _Q3 . ₃ ,
A series circuit of a variable resistor Rv for fine adjustment and a resistor _R4 for determining the upper limit of bias fine adjustment is provided, and a normal tape contact n, a chrome tape contact c, and a metal tape contact m are connected between the power supply terminal +B and the collector of transistor _Q1 . A tape select switch _S2 having a tape select switch S2, a resistor _R5 for determining a normal applied voltage, a resistor _R6 for determining a chrome applied voltage, and a resistor _R7 for determining a metal applied voltage connected to each contact point n, c, and m are provided. ing.

Note that the base of transistor _Q1 is a variable resistor Rv.
A bias circuit for transistor Q ₃ is formed by a series circuit of resistor R ₃ , variable resistor Rv, and resistor R ₄ . Further, the switching terminal of switch _S1 is grounded.

Therefore, by switching switch _S2 , the resistance
The voltage applied to the series circuit of R ₃ , variable resistor Rv, and resistor R ₄ changes according to resistors R ₅ , R ₆ , and R ₇ , and the impedance between the collector and emitter of transistor Q ₃ changes and the voltage between the collector and emitter changes. The voltage between them is controlled to a voltage corresponding to the type of tape used, and the voltage applied by the bias oscillation circuit is controlled to a voltage corresponding to the tape used.

On the other hand, if you want to compensate for differences in characteristics depending on the manufacturer of the tape you are using, or to adjust the sound quality to your preference, finely adjust the base current by varying the variable resistor Rv, and adjust the collector and emitter voltages of transistor _Q3 . The voltage applied to the bias oscillation circuit is finely adjusted by finely adjusting the voltage applied to the bias oscillation circuit, and the bias of both heads is finely adjusted. In addition, by finely adjusting the amount of bias of the head,
In particular, the high frequency characteristics change.

However, in the case of Figure 1, the voltage variable width ratio by the variable resistor Rv is the same for each type of tape, so the voltage variable width ratio between the collector and emitter of transistor _Q3 is the same, and both The variation ratio of the head bias amount is also the same.

The range of change in the tape's high frequency characteristics is
Generally, if the variation ratio of the bias amount is the same, it decreases in the order of normal tape, chrome tape, and metal tape. For example, with normal tape,
4dB, 2.5dB for chrome tape, and 1dB for metal tape.

Therefore, depending on the type of tape used, the range of change in the tape's high frequency characteristics due to the variable resistor Rv varies, and there is a drawback that the same amount of sound quality correction cannot be performed for tapes with different characteristics.

This idea was made with the above points in mind, and involved inserting the emitter and collector of a power supply voltage control transistor in series in the primary circuit of the bias oscillation circuit, switching the tape select switch, and finely adjusting the bias amount. In this tape recorder, the voltage applied to the bias oscillation circuit is controlled by varying the voltage between the emitter and the collector according to the type of tape used, and the amount of recording bias is varied. inserted in series to the ground side of the next-side electric circuit, and between the collector and base of the control transistor, and the switching terminal of the select switch;
A resistor for determining applied voltage having different resistance values, one end of which is connected to each of the plurality of contacts of the select switch, and a sliding piece, and one end of which is connected to the other end of each of the resistors for determining applied voltage, for fine adjustment of the amount of bias. a variable resistor is provided in series, and a connection point between the base of the control transistor and the other end of the fine adjustment variable resistor is connected to a power supply terminal via a bias fine adjustment upper limit determining resistor, The present invention is a tape recorder in which the variable range of high frequency characteristics based on fine adjustment of the voltage between the emitter and the collector is made almost the same regardless of the type of tape.

Therefore, if the type of tape used is normal tape, chrome tape, or metal tape,
Let the resistance values of the resistors for determining the applied voltage corresponding to each tape be rn, rc, rm (rm<rc<rn), and the resistance value between the sliding piece and the other end of the variable resistor for fine adjustment be rx.
The voltage between the emitter and collector of the control transistor is the resistance between the collector and base rm + rx, rc
+rx and rn+rx, and at this time, the voltage variable width ratio based on the voltage fine adjustment between the emitter and collector by the fine adjustment variable resistor varies depending on the type of tape used, and the voltage between the collector and emitter is controlled by The variable range of voltage increases in the order of normal tape, chrome tape, and metal tape, and the range of change in high frequency characteristics due to the voltage fine adjustment is made almost the same for each type of tape, and almost the same sound quality correction can be performed. It is something that

Next, we will introduce the tape recorder of this invention, part 1.
This will be explained in detail with reference to FIG. 2 showing an embodiment.

As shown in Fig. 2, a high frequency is generated on the secondary side of the transformer T by switching two NPN type oscillation transistors Q ₁ and Q ₂ that are push-pull connected to the primary side of the oscillation transformer T. A recording bias and an erasing bias are supplied to a recording/reproducing head (not shown) and an erasing head H, respectively.

In addition, C ₁ and C 2 in Figure 2 are capacitors for preventing separation _{deterioration, C 3 is} a resonance capacitor for determining the oscillation frequency, C ₄ , C ₅ , and C ₆ are capacitors for preventing abnormal oscillation, and C ₇ is the oscillation feedback amount. Determining capacitor, C ₈
is a power supply decoupling capacitor, _R1 is an emitter resistor for both transistors _Q1 and _Q2 , and _R2 is a bias resistor.

On the other hand, in order to control the voltage applied to the bias oscillation circuit, the emitter and collector of a PNP power supply voltage control transistor _Q3 are inserted into the ground side of the primary circuit of the bias oscillation circuit.
The applied voltage mentioned above is controlled by the voltage between the emitter and collector of _Q3 .

By the way, the base of transistor _Q3 is connected to the power supply terminal +B via resistor _R4 for determining the upper limit of bias fine adjustment.
The collector is connected to the recording contact r and the playback contact p.
The tape select switch S2 is connected to the recording contact r of the recording/playback switch _S1 , which has a normal contact n, a chrome contact c, and a metal contact m between the collector and base of _the transistor _Q3 . one terminal, one end is each contact n, c,
Fixed resistors connected to each of the resistors R5, _R5 , R6, R7, and R7 are connected to each of the fixed resistors, namely, a resistor R5 for determining the normal applied voltage, a resistor _R6 for determining the chrome applied voltage, and a resistor _R7 for determining the metal applied voltage.
A sliding piece and a variable resistor for fine adjustment with one end connected to the other end of each resistor R ₅ to _{R 7} and the other end connected to the base.
There is an RV.

And the resistance values rn, rc, rm of each resistor R ₅ to _{R 7} are rn
>rc>rm, and if the resistance value between the sliding piece and the other end of variable resistor Rv is rx, the combined resistance between the collector and base of transistor _Q3 based on the switching of the switch is (rm+rx)> (rc+rx)＞(rn
+rx).

Therefore, the voltage variable width ratio due to voltage fine adjustment of variable resistor Rv varies depending on the switching of switch _S2 ,
The variable width of the voltage between the emitter and collector of transistor _Q3 can be adjusted using normal tape, chrome tape,
The width increases in the order of metal tape, and the range of change in high frequency characteristics due to variable resistor Rv is almost the same for normal tape, chrome tape, and metal tape, making it possible to perform almost the same sound quality correction for each tape. can.

And the resistance for determining the lower limit of bias fine adjustment in Figure 1
Since there is no need to provide a resistor corresponding to R ₃ , the configuration can be simplified and lowered in cost compared to FIG. 1.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a part of a conventional tape recorder, and FIG. 2 is a wiring diagram of a main part of an embodiment of the tape recorder of this invention. Q ₃ ... Control transistor, S ₂ ... Tape select switch, R ₅ , R ₆ , R ₇ ... Normal, chrome, metal applied voltage determination resistor, Rv ... Variable resistance for fine adjustment, R ₄ ... Bias Fine adjustment upper limit determination resistor, +B...Power supply terminal.

Claims (1)

[Claim for Utility Model Registration] The emitter and collector of a power supply voltage control transistor are inserted in series in the primary circuit of a bias oscillation circuit, and the type of tape to be used can be changed by switching a tape select switch and finely adjusting the bias amount. In the tape recorder, the voltage applied to the bias oscillation circuit is controlled by varying the voltage between the emitter and the collector according to the amount of recording bias, and the emitter and the collector are connected in series to the ground side of the primary circuit. between the collector and base of the control transistor, and a switching terminal of the select switch;
A resistor for determining the applied voltage with one end connected to each of the plurality of contacts of the select switch, and a sliding piece and one end connected to the other end of each of the resistors for determining the applied voltage for fine adjustment of the amount of bias. a variable resistor is provided in series, and a connection point between the base of the control transistor and the other end of the fine adjustment variable resistor is connected to a power supply terminal via a bias fine adjustment upper limit determining resistor, A tape recorder in which the variable range of high frequency characteristics based on voltage fine adjustment between an emitter and a collector is made to be approximately the same regardless of the type of tape.