Recorder with analog recording of a digital audio signal

Abstract: 1. Audio recorder with analog recording 2.1 If an analog audio signal coming from a source of digital signals is fed to an audio recorder with analog recording deterioration of the AF audio signal can appear, caused by the characteristics of the cable. The object is to reduce this deterioration. 2.2 The audio recorder is equipped with an entry hub (B1) for a digital audio signal and a digital-to-analog converter (5) connected thereto. 2.3 Particularly for an audio compact cassette recorder for rerecording of the audio signal from a CD player. 3. Figure.

Description: Usual so-called audio compact cassette recorders operate with analog recording of the audio signal. Hereby, the AF audio signal comes, e.g. via an entry hub, from another audio device or a microphone or, in a so-called radio recorder, from the tuner intergrated in the audio recorder. It is also known fran JP-61-26908 to connect the AF entry of the audio recorder via a cable to an AF audio signal which as such originates from a source of digital audio signal, e.g. a CD player. In this case deterioration of the AF audio signal can occur, caused by the characteristics of the cable, particularly by its resistance, line inductivity and line capacity. For instance, the bandwidth of the audio signal transmitted can be reduced. Hereby the high quality, as such, of the audio signal originating from the digital source is reduced. It is the object of the invention to create a rerecording facility which causes no or only slight impairment of the quality of the audio signal to be recorded by the audio recorder. This task is solved by the invention described in claim 1. Advantageous developments of the invention are decribed in the subclaims. The invention is based on the following idea. If the audio signal primarily originates from a source of a digital audio signal it is of advantage to conduct the transmission up to the recording stage digitally as far and long as possible. The parameters of a cable indicated above have a smaller effect on a digital audio signal than on an analog AF audio signal as long as they do not introduce bit errors into the digital audio signal. For this reason the audio signal is transmitted digitally as far as possible, namely up to the input terminal of the audio recorder, and only inside the audio recorder converted into the analog audio signal necessary for recording by means of a digital-to-analog converter. Preferably, the audio recorder also has an output for a digital audio signal. This output supplies either the digital audio signal fed to the recorder after having been processed accordingly or the audio signal retrieved by reproduction in the recorder, accordingly, after analog-to-digital conversion. The recorder preferably has further inputs and outputs for an analog audio signal, whereby means of switching-over between the processing of a digital signal and an analog signal are provided. The invention is subsequently illustrated in an example by means of the drawing. The figure shows the block schematic diagram of an analog audio recorder together with a source of a digital audio signal. The audio recorder 1 with analog recording by means of a usual compact cassette represented in the figure contains on the whole the following hubs for incoming or outgoing analog or digital signals. B1 Input terminal for a digital audio signal to be recorded by the recorder 1 B2 Output terminal for an analog audio signal coming either from the reproduction route of the recorder or derived from the input digital audio signal B3 Input terminal for an analog audio signal for the recording or an analog-to-digital conversion B4 Output terminal for a digital audio signal retrieved from the incoming digital audio signal by processing B5 Output terminal for a digital audio signal retrieved from the analog reproduction route or from the incoming analog audio signal B6 Output terminal of a CD player with a digital audio signal. Several different operating modes of the audio recorder 1 represented in the figure are described below. Recording With an Incoming Digital Signal The CD player 2 at its output terminal B6 supplies a digital audio signal which is fed to the input terminal B1 of the audio recorder 1 via a rerecording cable. The digital audio signal arrives at the PLL demodulator 4 through the memory 3. The output signal of the demodulator 4 is fed to the digital-to-analog converter 5 which, via a low pass 6, generates the two analog audio signals L, R of a stereo audio signal. These signals through the change-over switch S1, which is in its left position, arrive at the AF preemphasis circuit 7 which preferably generates a signal preemphasis according to the Dolby or Highcom method. From here the processed AF audio signals L, R are fed to the analog recording unit 8 as such which comprises a recording amplifier and the recording heads for the audio tape. The change-over switch S1 is switched to the left position by the manually operated control button 9. Recording of an Analog Signal The analog AF audio signal is fed to the input terminal B3 and arrives at the circuit 7 via the amplifier 10 and the change-over switch S1 switched to its right position and is then fed to the recording unit 8. Reproduction with Analog Signal Output The AF audio signals, coming from the unit 8 via the circuit 7 and the change-over switch S1 being in its right position and the change-over switch S2 being in its right position, arrive at the output terminal B2 and can there be retrieved as analog AF audio signals L, R. Reproduction with Digital Audio Signal Output The AF audio signals L, R from the change-over switch S1 are fed to the analog-to-digital converter 11 and converted into a digital audio signal therein. This is present at the output terminal B5 and can be fed to e.g. a recording or reproduction device with digital signal processing. Switching-Over Between Analog and Digital Operation The switching-over, as described, between digital operation and analog operation by means of the change-over switches S1 and S2 can, instead of by the control button 9, also be conducted automatically. For this purpose on presence of a digital signal in the demodulator 4 a correcting variable Us is generated which operates the change-over switch S1 and other change-over switches if necessary. A manual switching-over by means of the button 9 is then no longer required. Operation as Digital-To-Analog Converter If a digital audio signal is fed to the input terminal B1 this can, instead of the recording or in addition to the recording, be fed to the output terminal B2 for an analog audio signal by means of the switch S2, e.g. for the reproduction or recording with an analog audio signal. This way the recorder 1 additionally serves as a digital-to-analog converter. Operation as Analog-To-Digital Converter If an analog audio signal is fed to the input terminal B3 this arrives, via the amplifier 10 and the change-over switch S2 being switched to the right position, at the inputs of the analog-to-digital converter 11, which supplies a corresponding digital audio signal at the output terminal B5, e.g. for a DAT recorder or another device with digital audio signal processing. This way the audio recorder 1 serves as an analog-to-digital converter for an audio signal independent of the recording. Processing of the Digital Audio Signal The digital audio signal fed in via the input terminal B1 arrives at the processing circuit 12. Therein the digital signal is processed. For example, the clock pulse or the signal are generated anew, bit errors are recognized and removed or time errors are compensated. This signal is present at the output terminal B4 as a processed signal. Particularly, the signal at the output terminal B4 is processed with respect to amplitude in such a way that the hub B4 can also be connected to a device with digital signal processing, e.g. another DAT recorder, a receiver or an active loud-speaker unit, located farther away, by means of a longer cable of e.g. 5 to 10 meters.

Claims: Audio recorder with analog recording of an audio signal and with input terminals for audio signals to be recorded, characterized in that the recorder (1) is equipped with an input terminal (B1) for a digital audio signal and a digital-to-analog converter (5) connected thereto. Recorder according to claim 1, characterized in that a change-over switch (S1) is used by which the analog route of recording (7, 8) can be switched to the output of the digital-to-analog converter (5) and to an entry hub (B3) for an analog AF audio signal as desired. Recorder according to claim 1, characterized in that a change-over switch (S2) is used by which the analog output signal of the digital-to-analog converter (5) can be switched to an output terminal (B2) for an analog AF audio signal. Recorder according to claim 2 or 3, characterized in that the change-over switch (S1, S2) is operated automatically by an identification signal derived from the signal which denotes the presence of a digital signal. Recording according to claim 1, characterized in that a PLL demodulator (4) lies between the input terminal (B1) for the digital audio signal and the digital-to-analog converter (5). Recorder according to claim 1, characterized in that an output terminal (B4) for a digital audio signal is used to which the input terminal (B1) for the digital audio signal is connected via a signal processing circuit (12). Recorder according to claim 1, characterized in that an output terminal (B5) for a digital audio signal is used to which the analog reproduction route or the input terminal (B3) for the analog audio signal is connected via an analog-to-digital converter (11).

Inventors: ISHIBASHI HIROAKI, ISHIBASHI, HIROAKI
Applicants: THOMSON BRANDT GMBH, DEUTSCHE THOMSON-BRANDT GMBH
Application year: 1989
Main classification: G11B20
IPC codes: G11B5, G11B15, G11B27, G11B20, G11B31