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  Analog Devices' SoundMAX 3.0 with SPX 
  May 30, 2001, 09:00am EDT 

CNR Makes an Appearance

By: Dan Mepham

Intelís CNR (Communications and Networking Riser) slots are a perfect companion for SoundMAX technology. In fact, it was features such as SoundMAX for which AMR/CNR were designed for in the first place.

By adding a small, inexpensive CNR riser card, SoundMAX 3.0 with SPX is now fully capable of 4-channel, 5.1-channel, and even digital output support.

SoundMAX CNR Riser

Fig 3. A SoundMAX Multi-channel CNR Riser. Notice the two small AD1885 CODECs used on the card. Each controls two additional audio channels (SR & SL, Center & Sub)

The riser we were equipped with featured two additional stereo minijacks, and an optical S/PDIF (Sony/Philips Digital InterFace) output. The first stereo minijack is for surround channels, while the second is used for the center and LFE (Low Frequency Effects) channels. When using either, the front stereo channels are provided through the minijack connector on the motherboard.

The riser is extremely small and inexpensive. As we mentioned, each AD1885 CODEC can handle two channels, so our riser incorporated two additional AD1885 CODECs, one to handle the two additional surround channels, and one to handle the center and LFE channels. Again, the IC located on the motherboard continues to handle the front right and left channels." alt="Channel Diagram" border=0>

Fig 4. The diagram illustrates how multiple CODECs can be daisy-chained together to add support for additional channels.

The optical output can be used to connect to DVD decoders, amplifiers, or other devices. It is certainly possible to base a design around a coaxial digital output, as opposed to an optical output, however our riser was equipped with an optical output only.

It is technically possible to produce AMR SoundMAX risers, although we donít expect to see any, as AMR is currently being phased out. Further, should even a CNR riser prove too costly, a designer could simply integrate one or two additional AD1885 ICs directly onto the motherboard as necessary, and have the entire 5.1-channel system on-board.

1. Introduction
2. AC'97, Too Cheap For Its Own Good?
3. SoundMAX, Taking AC'97 a Step Further
4. The Latest SoundMAX, SoundMAX 3.0 with SPX
5. CNR Makes an Appearance
6. Test Setup & Procedure
7. Test Results
8. Sound Quality
9. Conclusions

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