JPS5935870Y2 - Recording level adjustment circuit - Google Patents

Description

[Detailed explanation of the invention] For tape recorders etc. that have a noise reduction circuit,
Even if magnetic tapes with different tape sensitivities are used, it is necessary to ensure that the playback output level always maintains a constant relationship.
The recording level is set before the signal is actually recorded.

In this case, if the tape recorder used is a three-head type, tape monitoring is possible because the recorded signal can be played back at the same time as recording.

Therefore, it is easy to set the recording level with this type of tape recorder.

However, since tape monitoring is not possible with a two-head type tape recorder, it is necessary to repeat the recording/playback mode several times in order to perform the level setting described above.
Level setting operation is very troublesome.

The present invention aims to simplify this level setting operation, and like the 3-head type, it is possible to reliably set the optimum recording level by setting the level only once.

In this case, the present invention specifically achieves the above-mentioned object by making clever use of existing integrated circuits provided in the recording and reproducing system of the tape recorder.

An example of the present invention will be described in detail below with reference to the drawings.
FIG. 1 is a well-known system diagram necessary for explaining the present invention in a two-head type tape recorder.

The input signal supplied to the terminal 1 is supplied to the line amplifier 4 through the recording amplifier 2 and the recording volume 3, and its output is transmitted through the feedback circuit 4R and the recording equalizer amplifier 5 to the output of the bias oscillator 6, which is used for both recording and playback. The input signal is supplied to the magnetic head H and recorded.

The playback output of the magnetic head H is controlled by the recording/playback selector switch SW.
1 to the reproduction amplifier 8 and the above-mentioned line amplifier 4, and is amplified as desired.

9 is its output terminal, and a level meter 10 and its driving amplifier 11 are connected to this terminal 9.

12 is a feedback circuit provided in the equalizer amplifier 5;
Consists of multiple resistors and capacitors.

It goes without saying that the above-mentioned line amplifier 4 operates both as a recording amplifier and as a reproduction amplifier depending on the control voltage supplied thereto.

A terminal a provided on the integrated circuit 20 is an external terminal for this purpose, and in this example, the line amplifier 4 is made to operate as a recording amplifier by applying a control voltage.

Therefore, a changeover switch SW2 is provided between the external terminal a and the power supply terminal 15, and this switch is switched in conjunction with the recording/playback button.

Note that when the line amplifier 4 is used as a recording amplifier, an output is also obtained from the terminal d, which is used for source monitoring.

By the way, the above-mentioned line amplifier 4 and equalizer amplifier 5 are integrated.

20 indicates the integrated circuit.

As shown in the figure, the integrated circuit 20 used in this example has no external terminals on the transmission line 1 between the line amplifier 4 and the equalizer amplifier 5, which are used especially during recording, to separate this transmission line 1. This is the type that does not.

The present invention does not make any changes to this integrated circuit 20,
It was constructed in such a way that it could be skillfully used to achieve the intended purpose.

FIG. 2 shows an embodiment of the present invention.

In the figure, 21 is the recording side input terminal of the line amplifier 4 (
This is an oscillator for the reference signal Ss connected to the recording terminal (recording terminal) C, and is used only when setting the recording level.

In the present invention, for example, an auxiliary amplifier 23 is connected between the recording terminal C and the playback amplifier 8, and a feedback circuit 24 provided between the input and output of the auxiliary amplifier 23 is connected to a volume 2 for level setting.
5 are convertively connected via a setting switch SW3.

In the example shown in the figure, the feedback circuit 2 is made up of multiple resistors 24A to 24C.
4, and the above-mentioned volume 25 is connected to the connection point 11 only when setting the recording level.

The overall gain of the auxiliary amplifier 23 is equal to that of the equalizer amplifier 5.
Each constant is chosen to be equal to the overall gain of .

The volume 25 is connected to the feedback circuit 12 of the equalizer amplifier 5 during normal operation after level setting.

Therefore, the other contact (off contact) of the switch SW3 is connected to the connection point 12 of the feedback circuit 12, but this connection point 12 is connected to the fixed resistor 27 and the switching transistor Q.
a is connected.

That is, since the volume 25 is connected to the feedback circuit 24 during level setting, a fixed resistor 2T is connected to the volume 25 in order to equalize the gains of the equalizer amplifier 5 and the auxiliary amplifier 23 in this state. are connected.

The resistance value is selected to be equal to the intermediate value of the variable amount of the volume 25, for example.

A control voltage supplied to the line amplifier 4 is used to control the transistor Qa.

Therefore, the recording terminal of the selector switch SW2 is connected to the first control switch SW, and the switching is controlled so that the transistor Qa is turned on only during level setting.

In addition, since it is necessary to cut off the input signal during level setting, a control transistor Qb is connected in parallel to the transmission path of the input signal, and the above-mentioned transistor Qa
Similarly, the first control switch SW4 turns it on and off.
Off is controlled.

A second control switch SW5 is provided on the playback terminal side of the changeover switch SW2, and even during playback, and especially during level setting, a desired control voltage is supplied to the line amplifier 4, and the line amplifier 4 is used as a recording amplifier. It is designed to work as a.

Next, the adjustment procedure of the recording level adjustment circuit configured as described above will be explained.

First, the recording level is adjusted using a reference tape.

This adjustment operation is performed before shipping, and includes switches SW1. SW2 is switched as shown in the figure to put the tape recorder into recording mode, and switches SW3 to SW (which are switched in conjunction with each other) used for level setting are put into setting mode (ON side).

When this happens, transistor Qb turns on and the input signal is cut off, resulting in 1. At the same time, the transistor Qa is turned on, and the feedback circuit 12 of the equalizer amplifier 5 is connected to the setting volume 25 and a fixed resistor 2T having the same resistance value.

Therefore, the reference signal Ss is recorded through the equalizer amplifier 5 having a predetermined gain.

After recording the reference signal Ss, switch SW1゜SW
2 to switch to playback mode.

With the presence of the second control switch SW, even in the playback mode,
Since the predetermined control pressure is supplied to the line amplifier 4, the line amplifier 4 works as a recording amplifier, and therefore the playback output through the playback amplifier 8 and the auxiliary amplifier 23 is supplied to the line amplifier 4 to achieve the desired output. It is increased and widened as if it were.

Since the amplified output is obtained at the terminal d, the meter 10 is driven in accordance with the reproduced output.

Therefore, the auxiliary amplifier 23 is adjusted so that the indication on the meter 10 indicates an appropriate playback output level (for example, OVU level).
The fine adjustment variable resistor 28 provided at the output stage of is adjusted.

In this case, the auxiliary amplifier 23 has a setting volume 25 in its feedback circuit 24, and an equalizer amplifier 5 on the other hand.
A fixed resistor 27 is interposed in each of the feedback circuits 12,
Since the gains of both amplifiers are equal, if the gains of recording amplifier 2 and playback amplifier 8 are equal, when the output level during playback is at an appropriate level, the recording level at that time will also be at an appropriate level. You can say that.

Therefore, when a reference signal is recorded using a magnetic tape having a tape sensitivity different from that of the reference tape, the reproduced output will be different from that of the reference tape.

Therefore, in such a case, if the user adjusts the setting volume 25 to the appropriate level, when the actual signal is recorded, and therefore when the switches SW3 to SW are released from the setting mode (on the OFF side), Since this volume 25 is interposed in the feedback circuit 12 instead of the resistor 27, it is possible to record at an appropriate level.

As explained above, according to the structure of the present invention, a magnetic tape having any tape sensitivity can be set to an appropriate recording level by setting the level only once.

Therefore, in addition to simplifying the level setting operation, there is an effect that the existing integrated circuit 20 can be used as is without changing the design, such as increasing the number of external terminals.

In the embodiment described above, the auxiliary amplifier 23 is provided in the reproduction system and its gain is made equal to the gain of the equalizer amplifier 5, but the line amplifier 4 itself may also be used.

An example is shown in FIG.

In this example, an oscillator 21 is used which is set in advance so that the level of the reference signal Ss becomes a predetermined level.

Therefore, in this case, there is no need to connect the oscillator 21 to the human power stage of the line amplifier 4, and the oscillator 21 is connected to the output stage of the equalizer amplifier 5 as shown in the figure.

Even if connected to the input stage, there is no additional support.

Then, during level setting, the gain of the line amplifier 4 is adjusted.

Therefore, in this example, a new feedback circuit 31 is provided in parallel with the feedback circuit 4R.

The amount of feedback can be varied by a volume 25.

The gain of the equalizer amplifier 5 when the volume 25 with an intermediate resistance value is connected to the feedback circuit 12, and the gain of the line amplifier 4 when the volume 25 is connected to the other feedback circuit 31. are selected in advance so that they are equal.

Therefore, when reproducing the reference signal Ss, the level setting is completed by setting the volume 25 to an appropriate level while watching the meter 10.

After the level is set, turn the control switch SW
6, the feedback circuit 31 is cut off, and the changeover switch S
The adjusted volume 25 is connected to the feedback circuit 12 of the equalizer amplifier 5 by W3.

Even with this configuration, the level can be set with one adjustment.

With this configuration, the number of control switches used for level setting can be reduced as shown in the figure.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the main parts of a recording/playback system of a tape recorder, and FIGS. 2 and 3 are connection diagrams showing one embodiment of the present invention. 4 is a line amplifier, 5 is an equalizer amplifier, 21 is a reference signal oscillator, 23 is an auxiliary amplifier, and 25 is a volume for level setting.

Claims (1)

[Scope of utility model registration request] Line amplifier and recording equalizer amplifier are integrated,
In a recording level adjustment circuit using an integrated circuit in which there is no external terminal that can separate the transmission line between them, the volume for setting the reference level of the reference signal is connected to the feedback circuit of the equalizer amplifier mentioned above during normal recording. At the same time, when playing back a reference signal recorded at the reference level, the volume is connected to a feedback circuit of the auxiliary amplifier or the line amplifier that is intervened only during playback, and the gain of the auxiliary amplifier or the line amplifier is adjusted. A recording level adjustment circuit that allows the above to be controlled by the volume.