JPS6126908A - Analog recorder - Google Patents

Abstract

PURPOSE:To perform the analog recording of the reproduced signal given from a digital source with high quality by recording the D/A converted analog signal to a recording medium by means of an AC bias signal having a frequency corresponding to the D/A converted frequency. CONSTITUTION:A digital signal D10 obtained from a digital source CD10 of a CD player 15 is converted into an analog signal E12 by a D/A converter 12 to obtain a synchronizing signal S12 having a frequency corresponding to the D/A converting action. The signal E12 is supplied to a tape recorder 21 via an LPF 14; while the signal S12 is supplied to a synchronizing oscillator 26. The signal 14 obtained via a recording amplifier 16 is added with the output of an oscillator 26 by a mixer 18 for the recorder 21. Thus a bias current IR having an envelope corresponding to the output of the amplifier 16 is applied to a sound recording head 20. In case the signal S12 is not obtained, a bias signal is obtained from a PLL oscillation circuit 40 using a crystal oscillator 30. Thus the digital reproduced signal can be recorded in an analog form with high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field] The present invention relates to an analog recorder that records analog signals obtained through a digital transmission system with high quality. In particular, the present invention relates to an improvement in the method of applying an AC bias to an analog chip recorder for recording high-quality sound reproduced from digital equipment such as a compact disc (CD).

〔background〕

As a typical example of a system that uses digital technology to perform high-quality signal transmission, in addition to the CDs mentioned above, PCs that use VTRs
There are M recorders and PCM satellite communication systems. In these systems, analog information to be transmitted is divided at regular intervals along the time axis, and the analog level (amplitude component) within each divided section is converted. The digital signal thus obtained is later converted by a CD player or the like and reproduced as an analog music signal.

〔problem〕

When attempting to record a converted analog signal as described above on a car set tape or the like in high quality, the following problems arise with the conventional AC bias method.

The operation of converting a digital signal and returning it to an analog signal is
Usually, this is performed using the same sampling frequency as during ψ conversion. Taking a CD as an example, the sampling frequency is 44
．． At 1 kHz, conversions occur at a rate of 44,100 times per second. Then, the nine analog signal levels (LH) obtained by side conversion at a certain point (N) and the D at the next (N+1)
/Analog signal level obtained by A conversion (5w+1)
The signal level (L)l-LN+1) between the two is approximately linearly approximated by a low-pass filter or the like.

Approximate analog data obtained within the interval between the N-th conversion and the N+1-th conversion is susceptible to the effects of low-pass filters and the like, and has relatively low accuracy with respect to the original signal information.

In an AC bias type analog recorder, amplitude information corresponding to the envelope of an AC bias signal is recorded on a magnetic tape or the like. Therefore, unless the bead point of the AC bias signal wave forming the recording envelope corresponds accurately to the amplitude of the analog signal to be recorded, highly accurate (high quality) recording cannot be performed. However, in conventional AC bias type recorders, there is no clear synchronization relationship between the bias frequency and the sampling frequency of the side-converted analog signal to be recorded. For this reason, when a playback signal from a CD or the like is recorded using a conventional analog tape recorder or the like, the peak point of the AC bias wave does not always correspond correctly to the analog level that occurs at a certain timing after a desired continuous conversion operation. Rather, between the linear approximation levels (LN"""N+
1) The peak point of the AC bias wave often moves irregularly or unstablely. This is one of the causes of degrading the quality (sound quality) when an analog signal that has passed through a digital system is recorded by an analog recorder.

〔the purpose〕

An analog recorder that prevents the peak point of an AC bias wave from moving irregularly or unstablely on the level between the N-th analog level after 1st conversion and the N-)-1st analog level after conversion. It is an object of this invention to provide.

〔overview〕

To achieve the above object, the analog recorder of the present invention utilizes an AC bias signal that corresponds to (synchronizes with) the frequency of conversion. For example, if we take an analog tape recorder that records the playback sound of a CD player, we can convert the AC bias frequency to the integer ratio of the conversion frequency of 44.1 kHz (
44.1kHz, 88.2kHz, 132.
3 kHz, etc.) to prevent the peak point of the bias wave from moving irregularly or unstablely between the N-th and N+1-th D/A conversion converter bells.

〔Example〕

FIG. 1 shows the configuration of an analog recorder according to an embodiment of the present invention, together with a CD grayer 15 as a program source. Further, FIG. 2 illustrates the main waveforms of the configuration of FIG. 1.

The digital signal D10 (FIG. 2b) obtained from the digital source (CD) IO is converted by the D/A converter 12 into an analog signal E12 (FIG. 2C). A synchronization signal 812 (FIG. 2a) having a frequency (eg, 44.1 kHz) corresponding to this high conversion operation is obtained from the jet transducer 12.

The step analog signal E12 immediately after D/A conversion is converted by a low-pass filter (LPF) z4 into a reproduced signal rgt4 (FIG. 2C) having a smooth amplitude change.

The converted analog signal E14 is input to a recording amplifier 16 within the tape recorder 2.

The output of the amplifier 16 is superimposed on an AC bias signal F, 24 or E2B, which will be described later, in the mixer 18. Then, a bias current IR (FIG. 2 f) having an envelope corresponding to the output of the amplifier 16 is applied from the mixer 18 to the recording head 20.

The synchronous signal S 12 (44,1 kHz) is input to the synchronous oscillator 26. Then, a bias signal E26 (FIG. 2e) synchronized with the signal 812 is obtained from the oscillator 26. The frequency of signal F, 26 is, for example, 44.1
kHz or 88.2 kHz. Signal E26
The phase of is input to a phase shifter 24 whose phase shift amount is variable. From the phase shifter 24, a signal E24 (FIG. 2 d) whose waveform peak point timing corresponds to a predetermined position of the D/A converter signal E12 (FIG. 2 C) is obtained. Note that it is preferable to determine which position of the signal E12 the waveform peak of the bias signal E24 corresponds to by adjusting the phase shifter 24 mainly through hearing. Bias signal E24 synchronized with signal 8.12 is sent to mixer 18 via contact a of bias selection switch 22.

The above is a case where the synchronization signal 812 can be obtained from the CD 7' layer 15, but if the synchronization signal 812 cannot be obtained, the following may be done. That is, the PLL oscillation circuit 40 ensures stability of the oscillation frequency by the crystal oscillator 30.
A bias signal E40 (FIG. 2e) is obtained. The frequency of this signal E40 is an integer ratio (44, 1
kHz, 88.2 kHz, etc.). Signal E
The signal E400 phase adjustment relative to 12 is controlled by variable phase shifter 28
This is done by Bias signal E obtained from phase shifter 28
28 (FIG. 2d) is sent to mixer 18 via the contacts of switch 22.

〔effect〕

Since the frequency of the AC bias signal (E24.Ezs) corresponds to the frequency at the time of conversion (synchronization in a broad sense), the bias wave peak is the same as the Nth analog level of the digital signal (010,) and the N111th analog level. Do not move irregularly or erratically between levels. Therefore, the reproduced signal (EJ4) from the digital source can be recorded in analog form with high quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an analog recorder according to an embodiment of the present invention, and FIG. 2 is a diagram explaining the operation of the analog recorder shown in FIG. 10...Digital source, 12...I converter, 14
...Low pass filter, 15...CD7' layer,
16...Recording amplifier, 18...Mixer, 20...
Recording head, 2... Tape recorder, 22...
Bias selection switch, 24.28...phase shifter, 26
...Synchronous oscillator, 30...Crystal oscillator, 40...
PLL oscillation circuit.

Claims (1)

[Claims] An analog recorder records a D/A converted analog signal onto a recording medium using an AC bias signal having a frequency corresponding to the D/A conversion frequency.