JPH0358349A - Recording level adjusting device in recorder - Google Patents

Abstract

PURPOSE:To always perform recording at the optimum level by providing a means to adjust an attenuation quantity so as to set the optimum recording level corresponding to the kind of a recording medium when an analog signal corresponding to the full bit of digital audio data is inputted. CONSTITUTION:The analog signal corresponding to the full bit from a D/A input terminal 1 is supplied to a recording adjusting device 4. Meanwhile, information representing the kind of a tape detected with a tape selector switch 23 is outputted to the control circuit 5 of the recording adjusting device 4. The control circuit 5 selects the optimum recording level based on the information representing the kind of the tape, and outputs a control signal to the attenuator circuit 6 of the recording adjusting device 4. The attenuator circuit 6 attenuates the analog signal to the optimum recording level according to the control signal. Therefore, a voice signal adjusted to the optimum recording level can be outputted to a recording amplifier 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording level 7A adjustment device for a recording device that inputs and records an analog signal obtained by converting digital audio data from a digital audio source.

[Summary of the invention]

This invention allows digital audio data output from digital audio equipment such as a CD player or DAT to be
In a recording device that records an A-converted analog signal,
When an analog signal (2 Vrms) corresponding to a full bit of digital audio data is input, the amount of attenuation is set to the optimum recording level depending on the type of medium to be recorded, or the type of medium and the state of the noise reduction circuit. By providing a means for adjusting the level, the user can always record at the optimum level without having to worry about complicated optimum level conditions.

[Conventional technology]

The program source for a recording device such as a tape recorder is a high-level output such as a record player's phono equalizer, tuner, microphone amplifier, preamp output of another tape recorder, or standard-compliant 600Ω line output. For example, there are a wide variety of sources, such as phono pickups that do not pass through a preamplifier, microphones, telephone pickups, and low-level outputs such as DIN terminal outputs, and their levels vary.

Therefore, some devices had a separate microphone input terminal for extremely low levels, and others had separate input terminals for high and low levels, but in both cases, the recording level attenuator, or so-called recording volume The level variable width was set to be large.

On the other hand, with the aim of improving sound quality, the performance of magnetic tape, which is a recording medium, has also improved. Various tapes such as metal tape are commercially available.

Also, by suppressing perceptual tape noise using a dynamic noise reduction circuit, such as the Dolby system, it is possible to set the recording level low without impairing the S/N ratio and record with less distortion. There is also.

Furthermore, with the recent development of digital audio technology, CD (compact disc) players and
Digital audio equipment with excellent sound quality, such as DAT (digital audio tape recorder) and satellite broadcasting tuners, has become widespread, and audio signals from these digital audio sources are increasingly being recorded.

[Problem to be solved by the invention]

However, the better the sound quality of these sources is, the more conspicuous the deterioration of the sound quality of the reproduced sound will be if distortion occurs due to excessive recording level or decrease in S/N ratio due to insufficient recording level. Adjustment becomes important.

Even though the operability of recording equipment has become convenient and even amateurs can easily handle it, it is still difficult to monitor the level meter while recording and operate the volume, which has a large level variable range and requires fine adjustment. The point of adjusting to the optimal level has not changed since the early days.

Conventionally, there have been automatic recording level adjustment devices and excessive input level suppression devices, but they pick up noise (surrounding sounds) when there is no sound, or when there is a momentary high-level input, the sound immediately after it disappears, making it difficult to talk. Although it is effective for recording such as music, it is not suitable for recording where sound quality is important, such as music.

Furthermore, it is extremely difficult for amateurs to adjust the optimum level because they have to take into account changes in the optimum level depending on the type of tape and changes in the optimum level due to turning on and off the noise reduction circuit.

Also, even for experienced players who can master these conditions and make maximum use of the characteristics of tapes and circuits, it is important to record in advance the optimal level of recording of orchestral music that changes from pianissimo to fortitussimo, apart from rock music that continues fortitussimo. This is impossible unless tested.

However, in the case of analog audio technology, excessive level input can be avoided by only increasing distortion (excluding overmodulation of AM broadcasts and needle skipping of disk records), but in the case of digital audio technology, full bit ( Absolute maximum levels) must never be exceeded.

Therefore, the analog signal output of commercially available digital audio equipment such as CD players and DATs does not exceed the output level (standardized to 2Vrms) corresponding to full bits.

The present invention has been made in view of the above points, and allows the user to record the output from a digital audio source without having to worry about complex optimum level conditions, and to adjust the output according to the state of the recording medium or noise reduction circuit. To provide a recording level adjustment device that can always record at an optimum level.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a recording device that inputs and records an analog signal obtained by converting digital audio data from a digital audio source. Sometimes, means is provided to adjust the amount of attenuation so that the optimum recording level is achieved depending on the type of medium to be recorded.

Furthermore, when an analog signal corresponding to a full bit of digital audio data is input, a means is provided to adjust the amount of attenuation so that the optimum recording level is achieved depending on the type of recording medium and the state of the noise reduction circuit. You can.

[For production]

According to the recording level adjustment device constructed in this way, the analog input signal corresponding to full bits is adjusted to the optimal recording level that is preset according to the type of recording medium that is set.

Furthermore, when the noise reduction circuit is turned on or off, it is also possible to adjust the recording level to the optimum level according to its state and the type of recording medium.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a specific example of the recording system of a cassette tape recorder embodying the present invention, and the reproduction system will be omitted.

The input section includes a DA input terminal 1 into which an analog signal from a digital audio (rDAJ) device is input, a line input terminal 2 into which a high level signal is input, and a microphone input terminal 3 into which a low level signal is input. Become.

The signals input from the DA input terminal 1 pass through an attenuator circuit 6 for optimal level adjustment, the amount of attenuation of which is controlled by a control circuit 5 that constitutes a recording level adjustment device 4, and the output level corresponding to the full bit is input. When this happens, the level is adjusted to, for example, 6 dB higher than the optimum recording level and output to the next stage.

The attenuator 7 for fine level adjustment in the next stage is a variable resistor V
It is constructed by a series circuit of R and a resistor Ra, and a variable resistor V
The other end of the resistor Ra is connected to an input terminal 7a, into which the output of the recording level adjustment device 4 in the previous stage is input, the other end of the resistor Ra is grounded, and its output terminal 7b is connected to one input terminal of the input selector switch 8. .

The fine adjustment range of this attenuator is, for example, ±6 dB, and the adjustment knob (not shown) has a 1 dB adjustment range from -6 to +6.
A dB scale is provided for each B, so that the adjustment range is not wide and accurate reproducibility of recording level settings can be ensured.

Therefore, when the output level corresponding to full bits is input and the scale is set to OdB, the output of the attenuator is correctly at the optimal recording level.

The low-level signal input from the microphone input terminal 3 is amplified by one preamplifier, and then combined with the high-level signal input from the line input terminal 2.The low-level signal input from the microphone input terminal 3 is then combined with the high-level signal input from the line input terminal 2. The recording level is adjusted by the level volume 11 and output to the other input terminal of the input selector switch 8.

A D/A converted analog signal input from a digital audio device to DA input terminal 1, and a line input terminal 2,
An input changeover switch 8 that selects an analog signal input from an analog audio device input to the microphone input terminal 3 inputs a signal selected by an operator's instruction, for example, manually or by remote control, to the recording amplifier 12.

A level meter 13 is connected to the recording amplifier 12 and displays the recording level of the signal being recorded.

This level meter 13 has a specified indication delay.
It can be a U meter type or a peak level type that indicates the peak level of the recording signal, and high-end recording equipment has a level that displays both the average level and peak level of the L and R signals of the stereo signal. Meters are also used.

In addition, the recording amplifier 12 is equipped with a noise reduction circuit (hereinafter referred to as r) such as a Dolby C system.
If a noise reduction selector switch (hereinafter referred to as "rNR switch") 14 is built-in, the noise reduction selector switch (hereinafter referred to as "rNR switch") 15 is connected to turn on (activate) and off (deactivate) this NR circuit 14.

In this embodiment, when the NR switch 15 is off and the ungrounded terminal 15a is at ``H'', the NR circuit 14 is also turned off, and when the NR switch 15 is on and the terminal 15a is at ``L'', the NR circuit 14 is also on. become.

The voltage level of the terminal 15a of this NR switch 15 is N
It is output to the control circuit 5 of the recording level adjustment device 4 as an on/off detection signal of the R circuit 14.

The tape mechanism section 20 includes a magnetic tape 30 which is a recording medium.
A cassette half 31 containing the magnetic tape 30 is mounted, and the magnetic tape 30 runs at a constant speed (4.76 nn/see) in the direction of the arrow by a tape active system (not shown).

The magnetic tape 30 running at a constant speed is pressed against an erasing head 21 and a recording (and reproducing) head 22, which are respectively fixed, with a weak force.

In the recording mode, an AC erasing current supplied from a power supply (not shown) flows through the erasing head 21, and an audio signal current superimposed on the AC bias current output from the recording amplifier 12 flows through the recording (playback) head 22. ing.

The magnetic tape 30 is first erased by the erasing head 21 to erase the previously recorded signals, and then the recording head 22 erases the signals from the input terminals 1, 2, . The audio signal input from 3 is recorded.

Back section 31 of the cassette half 31 of the tape mechanism section 20
A tape selector switch 23 is provided at the portion corresponding to a, while a notch claw or the like for preventing erroneous erasure is provided on the back surface portion 51a of the cassette half 31.

FIG. 2 is an explanatory diagram showing the back surface portion 31a of the cassette half 31. FIG.

The same figure (A) shows a cassette half 31 for iron oxide-based normal position tape (type I) called normal tape, and its back side 31a has two cuttable accidental erasure prevention claws 32A and ES2B. It is provided.

After recording on side A of the cassette tape, the accidental erasure prevention claw 32
If you cut out A, you will no longer be able to record on side A again, and there is no risk that the recorded information will be erased by mistake.

Similarly, by cutting out the accidental erasure prevention claw 32B, the B side is protected.

FIG. 2(B) shows a cassette half 31 for chromium dioxide or cobalt iron-based high position tape (type ■) called chrome tape, and its back surface 31a
A recess 33 is provided near the two accidental erasure prevention claws 32A and 52B, respectively, to indicate that the tape is of type (2).

FIG. 2(C) shows a cassette half 31 for pure iron tape (type ■) called metal tape, and its back surface 31a is provided with two further recesses 34 near the center. The four recesses 33 and 34 indicate that the tape is of type (2).

The pairs of accidental erasure prevention claws 32A, 2B and recesses 33 and 34 shown in FIGS. Therefore, even if the cassette halves 31 are set upside down, they will be in the same position.

The tape selector switch 23 of the tape mechanism section 20 shown in FIG. 1 determines whether or not the set tape is recordable by detecting the presence or absence of these accidental erasure prevention claws 32A, 32B and recesses 33, 34. , or to detect the type of tape. When closing a cassette force bar (not shown) that covers the set cassette half 31, a pin or lever (not shown) is activated by a spring in conjunction with the cassette force bar. The back surface 31a of the half 31 is pressed into contact with the cassette 1 through the cassette 1.

If the accidental erasure prevention claws 32A and 32B are not cut out, the tip of the bottle will hit the back part 31a and stop, and each A
It is determined that the side and B side are recordable, and if they are notched, the tip of the pin advances further and it is determined that recording is prohibited.

A mechanism for detecting the presence or absence of this accidental erasure prevention claw is provided in all cassette recorders and is already known.

The mechanism for determining the type of tape by detecting the presence or absence of the recessed portion 55.34 is exactly the same.

Therefore, if the recesses 33 and 54 are not aligned, the set recording tape will be a normal position tape (type I).
If there is a concave portion 33 but no concave portion 34, it is a high position tape (type ■), and if both of the concave portions 3"5.34 are present, it is a metal tape (type ■).

The information indicating the type of tape detected by the tape selector switch 23 in this way is output to the recording amplifier 12 in order to match the performance of each tape and give the recording signal a pre-emphasis characteristic (frequency characteristic for recording). is,
At the same time, the signal is output to the control circuit 5 of the recording level adjustment device 4 so that the optimum recording level is selected according to the type of tape.

A control circuit 5 consisting of a microcomputer, a simple diode matrix, etc. that performs system control of the entire recording apparatus receives information indicating the type of tape input from a tape selector switch 23 and information input from an NR switch 15 indicating the ON state of the NR circuit 14. - Select the optimum recording level in combination with the off signal, and output the control signal to the attenuator circuit 6.

When recording an audio signal on a recording tape,
As the recording level increases, distortion increases, and as the recording level decreases, the S/N ratio deteriorates. In addition, a standard recording level is necessary to maintain compatibility with other recording devices, but this recording level also changes depending on the frequency, so
In the case of cassette tapes, the magnetic flux per 1 m++ of a tape recorded with 333 mm is tentatively specified as 250 pWb (picowave).

However, in order to improve the performance of later tapes, in reality, methods are used to determine the difference from the saturated recording level (MOL), and the amount of distortion when played back, for example, the recording level (SQL) at which distortion is 3%. Methods such as determining from

For example, while referring to the dynamic range, which is the ratio of MOL or SQL to the tape hiss noise level, saturation at the Takagi frequency at the maximum signal level is determined by the limitations imposed by the MOL value at the Takagi frequency and the SQL value at the Nakagusuku frequency. In order to widen the dynamic range, the optimal recording level is set to a level where there is little level drop due to noise and the distortion rate at the Nakagusuku frequency is small, and the dynamic range is wide.

Based on the characteristics of commercially available cassette tapes, when a normal position tape (type I) is taken as a standard, a high position tape (type ■) has a higher level by +2 dB, and a metal tape (type ■) has a higher level by about +4 dB.

In addition, when an NR system such as a Dolby C system is turned on, the dynamic range becomes wider because the hiss noise in the mid-high range that is audible to the listener during playback is reduced, so if you set the level to be about -3 dB lower than when it is off, The level drop due to saturation of the Takagi frequency and the distortion rate at the Nakagusuku frequency are smaller, making it possible to record with flat frequency characteristics, resulting in better sound quality.

The control circuit 5 of the recording level adjustment device M4 according to the present invention includes:
The attenuator circuit 6 sends a control signal instructing the optimum recording level corresponding to each case determined in this way.
Output to.

FIG. 3 is a circuit diagram showing an example of this attenuator circuit 6 together with an attenuator 7 for fine level adjustment.

The digital audio signal converted into an analog signal inputted from the DA input terminal 1 is unified at 2 Vrms at full bits (absolute maximum level).

The attenuator circuit 6 is composed of an L-type 4-terminal circuit in which an attenuation element consisting of a series circuit of transistors Q1 to Q5 and resistors R1 to R5, each of which is a switching element, is connected in parallel and then connected in series to a resistor RO. , an attenuator 7 is connected to its output side.

Let R7 be the equivalent input resistance seen from the input terminal 7a of the attenuator, which is a series circuit of the variable resistor VR and the resistor Ra.

A control signal from the control circuit 5 is inputted to each base of the transistors Q1 to Qs via a resistor, and if the control signal is at °H°, the transistors are turned on.

If all control signals are “L”, transistors Q1 to Q
5 is off, and the input terminal 7a of the attenuator 7 has a level divided by a voltage divider consisting of resistors RQ and R7, that is, a level 6 dB higher than the optimum recording level when the metal tape has the highest recording level and NR is off. .

Therefore, when the attenuator 7 for fine adjustment is set to the scale ○dB, the audio signal at the optimum recording level when metal tape (type IV) and NR is off is output from the output terminal 7b to the recording amplifier 12, and the attenuator 7 Adjustment allows level correction of ±6 dB.

For example, if the transistor Q1 is turned on when the normal position tape (type I) and NR are turned on, a divided voltage level is generated at the input terminal 7a due to the parallel resistance of resistors R1 and R7 and the resistor Ro, and the output Type I tape from terminal 7b. An audio signal at the optimum recording level when NR is off is output.

Similarly, tape types 1, Il [, ■
When the attenuator 7 is set to the OdB scale according to the on/off status of the NR circuit and the on/off status of the NR circuit, the audio signal adjusted to the optimum recording level is output to the recording amplifier 12.・You can always record at the optimal recording level that takes full advantage of the tape's performance without having to worry about turning it off.

Furthermore, the operator can freely modify the optimum level within a range of ±6 dB according to his/her favorite program source and the performance of the commonly used tape.

In this embodiment, the adjustment range of the adjustment adjustment for fine adjustment is ±6 db, but it is not limited to this range.

Furthermore, although the program source has been described above as the output of a digital audio device with a unified output level, the present invention can also be applied to cases where AM broadcasting or FM broadcasting is used as the program source.

In other words, when these program sources are used to modulate radio waves, overmodulation can cause a sudden increase in distortion and crosstalk with other channels, so the maximum level has already been regulated by the broadcasting station. Therefore, the maximum output of the combined tuner is also constant.

Therefore, once the amount of correction by Attenuator Tough has been determined, recording can always be made at the optimal recording level depending on the type of tape and whether the NR circuit is on or off, and at that time, the adjustment range can be limited using this recording level adjustment device. Therefore, the attenuator 7 with fine dB scale and good reproducibility can be used effectively.

As described above, this invention has been described as a second recording device having a built-in NR@ channel.
Although the embodiment according to the first invention has been described, it goes without saying that similar effects can be obtained by the first invention in the case of a recording device that does not have a built-in NR circuit.

〔Effect of the invention〕

As explained above, according to the present invention, when recording the output from a digital audio source, the user does not have to worry about complex optimum level conditions, and the optimum level is always set according to the state of the recording medium or the noise reduction circuit. It is possible to provide a recording level adjustment device that can record at.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a specific configuration example of the recording system of a cassette tape recorder embodying the present invention, Fig. 2 is an explanatory diagram showing the back side of a cassette half, and Fig. 3 is an attenuator circuit of this embodiment. It is a circuit diagram showing an example. 4... Recording level U8 adjustment device 5... Control circuit 6... Attenuator times 3i! (Attenuation adjustment means) 14
... Noise reduction circuit (NR circuit, noise reduction circuit) 1 5 ... Noise reduction selector switch (NR switch) 23 ... Tape selector switch

Claims (1)

[Scope of Claims] 1. In a recording device that inputs and records an analog signal obtained by converting digital audio data from a digital audio source, when an analog signal corresponding to full bits of the digital audio data is input, an attempt to record is made. 1. A recording level adjustment device comprising means for adjusting an amount of attenuation so as to obtain an optimum recording level depending on the type of medium to be recorded. 2. In a recording device that inputs and records an analog signal obtained by converting digital audio data from a digital audio source, when an analog signal corresponding to full bits of the digital audio data is input, the type of medium to be recorded and the noise 1. A recording level adjustment device comprising means for adjusting an amount of attenuation so that an optimum recording level is obtained depending on a state of a reduction circuit.