X-bit labs

Contemporary Integrated Sound Solutions. Part II (page 3)

Category: Multimedia

by Sergey Samarin

[ 11/04/2003 | 09:21 PM ]

Analog Devices AD1985: Child of Honorable Parents

The world-renowned semiconductor company, Analog Devices Inc., has long been producing AC’97 codecs for mainboards and add-on sound cards. They work in close contact with such giants as Intel and Microsoft as well as with other big industry names. As soon as the 2.3 edition of the AC’97 specification came out, Analog Devices introduced a compliant codec, supported by fully functional software. So, we can already enjoy that Jack Sensing technology. But let’s be methodical and examine the codec thoroughly first.

The AD1985 codec was specially developed by Analog Devices for Intel’s ICH4 and ICH5 South Bridges. So, I venture a supposition that its lifetime will match that of mainboards with these South Bridges.

AD1985 codec from Analog Device with Jack Sensing support

The codec is an amalgamation of advanced technologies both in hardware and software departments. Analog Devices itself designs the codec, while the codec’s software comes under the SoundMAX trademark. The trademark is property of Analog Devices and was registered in the Integrated Audio Group within the framework of the strategic alliance of Intel and ADI. First, we will examine the hardware stuffing of the codec and then estimate the efficiency of the software.

The hardware part of the AD1985 codec features:

• Six-channel DAC for 5.1 Surround;
• 20-bit resolution for all internal DACs;
• Dynamic range of 90dB;
• Integrated amplifier for headphones;
• Integrated parametric equalizer;
• User-selected microphone input with stereophonic preamplifier;
• Phase-lock auto-control;
• Jack Sensing (automatic recognition of connections).

I would like to point out the new auxiliary circuit called Analog Mixing Control Jack Sense. This circuit allows the operating system to identify the attached analog audio device. If you are interested in getting more detailed info on the AD1985 codec, you can find it at the Analog Devices website in a PDF-file.

ASUS was one of the first manufacturers to use the AD1985 codec in its mainboards. Why? ASUS just wanted to roll out a mainboard series featuring the integrated “Artificial Intelligence” technology. The codec from Analog Devices is capable of auto-detecting the connected audio devices, which is an intelligent function, of course. This gave ASUS the  reason for touting the audio subsystem of its new mainboards as Artificial Intelligence Audio (AI-Audio). Every manufacturer is prone to puff up the advantages of its products (if any). The ASUS website claims the mainboards of the AI series use the world’s first intelligent audio codec. Do not let the words mislead you into thinking it’s the only one available. Besides the AD1985, there are six-channel codecs from Realtek (ALC655 and ALC658), which support Jack Sensing, too. We are not going to have them in this review, though.