JPH0385008A - Audio equipment - Google Patents

Abstract

PURPOSE:To reduce the cost and to save the space by forming a digital volume or an A/D converter with a D/A converter, an amplitude data output section and a multiplier type D/A converter so as to utilize the performance of a CD without any degrading. CONSTITUTION:A DSP(digital signal processor) 11 applies a prescribed processing to an inputted digital audio data. A 16-20 bit data of the output is converted into an analog audio signal ADS by a D/A converter 12 and inputted to a Vref terminal of the multiplier type A/D converter 15. On the other hand, a CPU 14 inputs a volume data VDT to a digital data input terminal of the converter 15 in response to the manipulation quantity of a sound volume adjustment operation key 13 and the converter 15 multiplies the inputs to output an analog audio signal ADS'. Thus, the amplitude of the signal ADS is controlled based on the volume data VDT.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an audio device, and particularly to an audio device having a digital volume and a digital-to-analog converter with good performance.

<Prior art> In order to adjust the signal level in an audio device into which digital audio signals are input, there are two methods: (1) attenuating or increasing the signal level while keeping it digital; and (2)
There is a method of converting to an analog signal and then adjusting the level.

<Problem to be solved by the invention> In the digital level adjustment method, digital data is calculated and the number of bits is apparently compressed or expanded, but this may cause problems in sound quality such as increase in quantization noise and disappearance of low-level sounds. The problem of deterioration arises.

On the other hand, in the method of converting to an analog signal and then adjusting the level, an analog volume (including a motorized volume) or an electronic volume is used. However, when using an analog volume, there are problems in that it requires space, is expensive, has design limitations, and is not compatible with remote control.

On the other hand, when using an electronic volume, the performance of the electronic volume in terms of dynamic range, S/N ratio, distortion rate, etc. is currently poor compared to the performance of a CD, so it is said that the performance of the CD will be degraded. There's a problem.

From the foregoing, it is an object of the present invention to provide an audio device equipped with a novel signal level control means that can solve the conventional problems.

Another object of the present invention is to provide a digital-to-analog converter that converts a digital volume or floating point data into an analog signal as a circuit embodying the signal level control means.

<Means for Solving the Problems> In the present invention, the above problems are solved by an AD converter that converts digital data into an analog signal, and an amplitude that outputs digital amplitude data related to the amplitude of the analog signal that is the AD conversion output. It is distantly related to the data output section and the multiplication type DA converter.

<Operation> A DA converter converts digital data into an analog signal, outputs digital amplitude data related to the amplitude of the analog signal, and multiplies the analog signal and digital amplitude data by a multiplication type DA converter. It also outputs an analog audio signal.

<Embodiment> FIG. 1 is a block diagram of a digital volume which is an embodiment of the signal level tM adjusting means according to the present invention, and 11 is a DSP (digital signal processor).
Then, predetermined processing (left and right channel separation processing, high cut processing, equalization processing, pass/treble processing, loudness processing, etc.) is applied to the input digital audio data.The output is 16 to 20 bit data. 12 is a DA converter that converts the output audio data of the DSP into an analog audio signal ADS.

13 is an operation key for volume up/down; 14 is a system controller that controls the entire device; for example, 8-bit volume data VD according to the amount of operation of key 13;
Generate T. 15 is an 8-bit multiplication type DA converter, which receives the analog audio signal ADS at the Vraf terminal, and the volume data VDT at the digital data input terminal, and multiplies these to output the analog audio signal ADS'. do.

That is, the DA converter 12 converts digital audio data into an analog signal ADS, and the system controller 14 generates a numerical value corresponding to the amount of operation of the volume adjustment operation key 14 as volume data (amplitude data) VDT, and these analog signals ADS and volume data VDT are multiplied by a multiplication type DA converter 15 to output an analog audio signal ADS'. Thereby, the amplitude of the audio signal ADS' is controlled based on the volume data VDT.

According to this method, unlike conventional digital processing, the bit length is not apparently compressed or expanded, so quantization noise does not increase or small levels disappear.
It also eliminates the problems of conventional analog volume and electronic volume.

FIG. 2 is a block diagram showing an embodiment of a digital-to-analog converter as a signal level tAa means according to the present invention, and 21 is a DSP (DSP) that performs predetermined floating-point processing on input digital audio data. Floating point DSP), 22 receives floating point data which is the processing result of the floating point DSP bit serially, and 16 to 2
This is a mantissa/exponent pre-circuit that separates a 0-bit mantissa part MAN and an 8-bit exponent part EXP and outputs them as parallel data.

23 is D for converting the mantissa part MAN into an analog signal ADS
The A converter 24 is an 8-bit multiplication type DA converter, which inputs the analog signal ADS to the V ref terminal, and inputs the exponent part EXP to the digital data input terminal, and multiplies these to generate analog audio. Signal ADS'
Output.

That is, digital audio data processed by DSP using floating point arithmetic is separated into a mantissa part MAN and an exponent part EXP by a separation circuit 22, and then the mantissa part MAN is converted into an analog signal ADS, and these analog signals ADS and exponent part EXP are separated. are multiplied by the multiplication type DA converter 24 to output an analog audio signal ADS'. This allows digital data in floating point format to be converted into analog signals with a simple configuration and with good accuracy. In this case, the exponent part EXP is the amplitude control data.

<Effects of the Invention> According to the present invention, there is provided an AD converter that converts digital data into an analog signal, an amplitude data output section that outputs digital amplitude data related to the amplitude of the analog signal, and an amplitude data output section that outputs digital amplitude data related to the amplitude of the analog signal. Since the digital volume or analog-to-digital converter is configured with a multiplication-type DA converter that multiplies the amplitude data and outputs an analog audio signal, the conventional problems can be solved.

Furthermore, the performance of the CD can be brought out as is, and the DA converter and the multiplication type DA converter can be configured in one chip, which reduces costs and space, and furthermore, makes it possible to support remote control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital volume according to the present invention, and FIG. 2 is a block diagram showing an embodiment of a digital-to-analog converter according to the present invention. 11... DSP 12... DA converter 13... Volume adjustment operation key 14... System controller 15... Multiplying type DA converter 21... Floating point DSP 22... Mantissa/exponent separation circuit 23... DA converter 24... Multiplying DA converter

Claims (3)

[Claims] (1) An AD converter that converts digital audio data into an analog signal, an amplitude data output section that outputs digital amplitude data related to the amplitude of the analog signal, and a multiplier that multiplies the analog signal and digital amplitude data. An audio device characterized by having a multiplication type DA converter that outputs an analog audio signal. (2) The amplitude data output section includes a volume adjustment operation means;
2. The audio device according to claim 1, further comprising means for outputting a numerical value corresponding to the amount of operation of said operating means as amplitude data. (3) A digital signal processor that performs predetermined processing on digital audio data using floating-point arithmetic, and a digital signal processor that separates the floating-point format digital audio data output from the digital signal processor into a mantissa and an exponent. an AD converter that converts the mantissa part into an analog signal; and a multiplication type DA converter that multiplies the analog signal and a digital exponent part to output an analog audio signal. audio equipment.