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8 décembre 2010 3 08 /12 /décembre /2010 16:27

This serie of 4 articles will cover in deep sound in a PC.

Part One : The basics and theory of sound

Part Two : Implementation of the Sound Processing at the Hardware level

Part Three : The various standards in Sound ( Cables, Standards, Hi Definition )

Part Four : Various topics and issues about PC Sound ( EAX, HDCP, PAP, Software issues )

Part Two : Implementation of the Sound Processing at the Hardware level

The different hardware sound architectures :

Sound is implemented at a hardware level using different hardware architectures : codec, soundcard, hdmi audio bridging, hdmi with discrete audio codec.

1. Audio using a codec

The codec implementation is by far the cheapest and most widespread implementation of audio in a PC these days. Codec implementation has reached a high enough quality to be fully satisfying to most users.

Here is the basic design ( click to enlarge ) :


Chipset Codec


The Audio Controller, located in thhe southbridge, performs most of the tasks : mixing channels, setting levels, special effects. It should be notted that the Audio Controller is just a controller. The actual computing is done by the CPU.

The Audio Codec is a separate chip, located on the motherboard. These days it is merely a ADC / DAC converter, not even mixing channels anymore, the mixing duty being done by the Audio Controller. This Codec chip is also named an AUDIO PHY.

Let's look at some detailed technical diagrams now. Here is an Intel southbridge Audio Codec implementation ( click to enlarge ) :


Notice the two Serial Datas links between the southbridge and the codec, and the digital and analog lines from the codec to the back panel IOs.



Let's look at the implementation on an AMD 785G chipset board ( for an example : ASUS ASUS M4A785TD-V EVO. 785G Northbridge, SB710 Southbridge, VIA VT1708S Audio Codec ). This is a pretty good multimedia / HTPC motherboard,  so we'll look at its specs all along this ' Travelling with sound ' serie ( click to enlarge ) .



( source : AMD official documentation )


Here is the internal diagram of a part of an Intel Southbridge. Notice the Intel High Definition Audio block in the diagram ( click to enlarge ) :



( source : Hardware secrets )



and last, here are the internal diagrams of the AD1888 and AD1988 A/B Audio Codecs ( click to enlarge ).

AD1888 :



the AD1988 A/B ( click to enlarge ) :


AD1988A 1988B






( To Be Continued ... )


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