JPS649642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a recording amplifier and a high frequency signal generator that supplies a bias magnetization signal to at least a magnetic recording head, and mixes already existing recorded information during the second and subsequent recording processes. The present invention relates to a circuit arrangement for a magnetic recording device in which the mixing ratio of the useful signal and the magnitude of the bias magnetization signal can be selected via a regulating device.

For example, such devices are used to record sound on amateur talkie film. Therefore, for example, the first
In the first recording process, the background music recorded on the magnetic recording track of the small film is played, and in the second recording process, the background music signal is attenuated and a voice comment is recorded. The volume of the later recorded comment signal or the attenuation rate of the background music signal can be adjusted by the user of the magnetic recording device using a so-called volume control device. In fact, such known volume control devices have a resistance which can be varied by the user, in which case the resistance is connected in parallel to the magnetic recording head. Depending on the selection of the resistance value of the adjustable resistor, the high frequency bias magnetization signal and the useful signal to be recorded are attenuated in different proportions. With such a known circuit arrangement, it is possible to change the amplitude of the high-frequency signal simultaneously with the amplitude of the useful signal, without causing acoustic disturbances during reproduction.

However, it is disadvantageous that it is not possible to replace a variable resistor, which is used, for example, as a volume control device, by an internal resistance of a semiconductor control element and to control the mixing process by means of a control DC signal. For example, in such a method, in order to simplify the operation of the device, it is necessary to use a microprocessor or the like as an auxiliary device for recording the sound or as a program control device for the program for recording the sound. The problem on which the invention is based is therefore to provide a magnetic recording device which avoids the drawbacks of such known devices and which can be controlled by program control electronics, for example in the "trick mixing" mode of operation. It is. According to the invention, this problem is solved in a circuit arrangement of the type mentioned at the outset by providing a low-pass filter for the useful signal, the limiting frequency of which is made variable by means of an adjusting device, and the amplitude of the useful signal and the bias magnetization The limit frequency of the low-pass filter is set low in accordance with the reduction in the amplitude of the signal, and the limit frequency of the low-pass filter is set in accordance with the increase in the amplitude of the effective signal and the amplitude of the bias magnetization signal. Solved by setting it higher. With such a special method, if the current flowing through the magnetic recording head is substantially constant and the amplitude of the bias magnetization signal is varied (decreased), the level at which high frequency useful signals are recorded will increase. It disappears.

The invention will now be explained with reference to illustrated embodiments.

FIG. 1 shows in block diagram form the circuit arrangement of a magnetic recording device with a known volume control device. A microphone, a record player, etc. can be connected to the preamplifier 2 via the terminal 1. The preamplifier 2 has a regulating circuit 3 with a regulating element 4, due to which there is a substantially constant voltage at the output 5 of the preamplifier 2, independent of the magnitude of the signal at the input terminal 1. A signal having a constant amplitude and to be recorded on a magnetic recording track (not shown) of a magnetic tape or motion picture film is supplied via a recording amplifier 6 and a magnetic recording head 7. The bias magnetization signal necessary for distortion-free recording is generated by a high frequency oscillator 8 and supplied to the magnetic recording head 7. Oscillator 8 is also used to power an erase head, which is only shown schematically. The effective signal is recorded by the recording amplifier 6.
The signal is supplied from the output side of the magnetic recording head 7 through a resistor 9 having a high resistance value. Since the resistor 9 is also used as a linearizing resistor, a quasi-steady recording current flows through the magnetic recording head 7. The high resistance value resistor 9 is also used to decouple the recording amplifier 6 from high frequency signals.

A variable resistor 1 used as a volume adjustment device to mix other information with already recorded information, that is, to perform so-called trick mixing.
0 (potentiometer) resistance value should be decreased. This makes it possible to attenuate or reduce the amplitude of the high frequency bias magnetization signal simultaneously with the amplitude of the useful signal. However, since a constant recording current flows through the magnetic recording head 7, if the variable resistor 10 is not used to leak the reference potential, the magnetic recording head 7 will have a large Changing the amplitude of the bias magnetization signal due to the impedance will increase the level of the high signal frequency portion of the useful signal. However, unlike the impedance of the magnetic recording head, the variable resistor 10 has a small resistance value for high frequencies, which prevents the voltage level of high frequencies from increasing in the magnetic recording head, resulting in balanced acoustic characteristics. will be obtained. However, when controlling the circuit device or the volume control device (variable resistor 10) shown in FIG. 1 with a DC signal, the magnetic recording head 7
cannot be used to connect a volume control device to the Connecting the variable resistor as an input voltage divider to the recording amplifier 6, for example mechanically in parallel with an adjustment device for the amplitude of the bias magnetization signal generator 8, will increase the level of high frequencies. This is because in that case the current of the high frequency useful signal part cannot flow through the variable resistor 10 of FIG.

FIG. 2 shows a circuit arrangement with which an adjustable voltage divider or variable resistor can be connected at the input side of the recording amplifier 6 and to obtain a balanced acoustic characteristic, ie without increasing the level of the high useful signal frequency part. . In the embodiment of FIG. 2, circuit elements corresponding to those of the embodiment of FIG. 1 are designated by the same numbers. The variable resistor 11 has two taps 12 and 13, to which capacitors 14 and 15 are connected. These capacitors ensure that when the slider 16 of the variable resistor 11 (potentiometer, input voltage divider) has a lower position, the useful signal to be transmitted is supplied to the magnetic recording head 7 with a small amplitude. Capacitors 14 and 15 act as frequency-selective circuit elements to reproduce the recorded information by passing a correspondingly high frequency portion of the signal when voltage divider 11 is adjusted to reduce the amplitude of the signal. In case you have a challenge to prevent the level from increasing.
However, in some cases, the bias magnetization amplitude should be adjusted even when inserting existing recorded information with a small amplitude, so a potentiometer 17 is linked to the potentiometer 11. similarly attenuates its amplitude by the supply voltage of the oscillator 8. Further, the constituent parts described above in the embodiment of FIG. 3 are designated by the same reference numerals. In FIG. 3, an operational amplifier having an inverting input side and a non-inverting input side is used as the recording amplifier 6. The useful signal is supplied via a preamplifier (not shown) to terminal 5 and is applied via resistors R1 and R2 to the inverting input of the operational amplifier. The operational amplifier has a negative feedback circuit with a resistor R3.
A regulating element RBL is connected between the series connection of the two resistors R1 and R2, with which the effective signal level can be controlled. The adjusting element consists of the collector-emitter of a Darlington transistor T, the base electrode of which is controlled by the slider of a potentiometer 18. potentiometer 18
is connected to the operating power supply, and by adjusting the slider in each case, the Darlington transistor T is rendered conductive to varying degrees, so that the internal resistance decreases or increases accordingly. The internal resistance corresponds to the variable resistance RBL and is determined by the amplification factor of the recording amplifier 6 configured using an operational amplifier. If the resistor RBL has a high resistance, the amplification factor V is determined by V=R3/R1+R2. If, on the other hand, RBL has a small value or RBL has a low resistance, the amplification factor V is determined by the formula V=R3/R2+RBL. In some applications, the value of resistor R1 is
Resistor R1 is ignored since it is chosen large relative to the value of RBL. From the above equation, it can be seen that when the internal resistance of the adjustment element T is high, the amplification factor of the operational amplifier 6 becomes small. However, in the circuit device shown in FIG. 3, even if the amplification factor of the operational amplifier 6 is adjusted to a relatively large value by making the adjustment element T or the variable resistor RBL relatively low in resistance, it is possible to select a large attenuation of the effective signal. It is configured as follows. The potentiometer 18 which controls the adjusting element T is also used at the same time to adjust the amplitude of the bias magnetization signal for the magnetic recording head 7. For this purpose, the slider is connected to the control input of the high-frequency signal generator 8. For example, by means of a signal applied to the slider of potentiometer 18, the magnitude of the operating voltage of oscillator 8 can be controlled, so-called balanced oscillators being quite suitable as oscillators with controllable amplitude. Therefore, a predetermined recording current flows through the magnetic recording head 7 via the linearizing resistor 9, and at the same time, the effective signal applied to the input side of the recording amplifier 6 is attenuated, and the amplitude of the bias magnetization signal is also reduced. Measures should be taken to avoid increasing the level of the frequency part. This is done by means of an adjustable capacitor 19, by means of which it is possible to define the upper frequency limit of the signal transmitted by the operational amplifier. This is illustrated in the diagram of FIG. 4, where the horizontal axis shows the frequency and the vertical axis shows the amplification factor of the operational amplifier 6. The operational amplifier is essentially constructed as a low-pass filter, the upper frequency limit of which can be shifted depending on the selected amplification factor. As shown by straight line a, when the amplification factor is large, the limit frequency is relatively small. If the amplification factor is very small, the limit frequency is relatively high, for example 10 KHz, as evidenced by straight line b. Also, straight line c
As shown in , an approximately intermediate amplification factor can be obtained at an intermediate amplification factor. Above the limit frequency, the amplification factor of the recording amplifier 6 decreases with a slope of 20 dB per 10 steps or 6 dB per octave. Therefore, in response to adjusting the volume control device (potentiometer 18), the level of the higher signal frequencies is reduced so that the level of the higher frequencies does not increase during playback. Alternatively, instead of the potentiometer 18 supplying a freely selectable control signal for the adjusting element T and the amplitude-adjustable bias magnetization signal oscillator 8, a direct current may be supplied from another power source. Control signals can also be used. For example, by using a DC signal stored in a microcomputer or the like and supplied during a predetermined program process, even an amateur can easily record sound.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a known so-called volume adjustment device, FIG. 2 is a block diagram showing a first embodiment according to the present invention, and FIG. 3 is a block diagram showing a second embodiment according to the present invention. FIG. 4 is a diagram illustrating the operation of the apparatus of FIG. 3. 2... Preamplifier, 3... Adjustment circuit, 4... Adjustment element, 6... Recording amplifier, 7... Magnetic recording head, 8... High frequency oscillator.

Claims (1)

[Claims] 1. A recording amplifier and a high frequency signal generator that supplies a bias magnetization signal to at least a magnetic recording head, and is configured to mix with already existing recorded information in the second and subsequent recording processes. , in which the mixing ratio of the useful signal and the magnitude of the bias magnetization signal can be selected via a regulating device, in which the low-pass filters 11, 14, 15, 16, for the useful signal are provided. 6,
RBL, R2, and R3 are provided, and the limit frequency of the low-pass filter is made variable by an adjustment device 18;
In response to decreasing the amplitude of the effective signal and the amplitude of the bias magnetization signal, the limit frequency of the low-pass filter is set low, and in response to increasing the amplitude of the effective signal and the bias magnetization signal. A circuit device for a magnetic recording device, characterized in that the limit frequency of a low-pass filter is set high. 2. A variable voltage divider 11, 16 is provided to adjust the amplitude of the useful signal to be recorded, said voltage divider having at least one voltage divider for the frequency-selecting circuit element 14, 15.
having two fixed taps 12, said circuit elements 14, 15 pass the higher frequency part of the useful signal to be recorded when the voltage dividers 11, 16 are adjusted so that the amplitude of the useful signal is small; 2. The circuit arrangement according to claim 1, wherein a control device 17 for controlling the amplitude of the bias magnetization signal in the same direction is mechanically and/or electrically coupled to the adjustment device of the variable voltage divider 11, 16. . 3. A valid signal is fed via a first resistor R2 to the inverting input (-) of an operational amplifier 6 with a negative feedback circuit with a second resistor R3, in which case the adjustable resistor RBL is set to a reference potential. A circuit 19 for selecting a frequency from the outside is connected to the first resistor R2, and a circuit 19 for selecting an external frequency is connected to the operational amplifier 6 to set the upper limit transmission frequency of the operational amplifier in relation to a predetermined amplification factor of the operational amplifier. 2. The circuit device according to claim 1, wherein the amplification factor and upper limit transmission frequency of the operational amplifier 6 are adjusted by changing the resistance value of the adjustable resistor RBL. 4. The adjustable resistance RBL is formed by the internal resistance of the semiconductor element T, and the control signal of the semiconductor element can also be used to adjust the amplitude of the bias magnetization signal. circuit device.