T23 SPDIF

[UnixNut]

Heya!

I've been using my T23 for playing music (as I now use my X41 as my main laptop), and while digging round the sound cards capabilities, I found that is has a SPDIF output (apparently it also supports surround sound):

front:CARD=I82801CAICH3,DEV=0
Intel 82801CA-ICH3, Intel 82801CA-ICH3
Front speakers
surround40:CARD=I82801CAICH3,DEV=0
Intel 82801CA-ICH3, Intel 82801CA-ICH3
4.0 Surround output to Front and Rear speakers
surround41:CARD=I82801CAICH3,DEV=0
Intel 82801CA-ICH3, Intel 82801CA-ICH3
4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=I82801CAICH3,DEV=0
Intel 82801CA-ICH3, Intel 82801CA-ICH3
5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=I82801CAICH3,DEV=0
Intel 82801CA-ICH3, Intel 82801CA-ICH3
5.1 Surround output to Front, Center, Rear and Subwoofer speakers
iec958:CARD=I82801CAICH3,DEV=0
Intel 82801CA-ICH3, Intel 82801CA-ICH3
IEC958 (S/PDIF) Digital Audio Output
null
Discard all samples (playback) or generate zero samples (capture)

If this is correct and the card supports it, how can I make use of the SPDIF? Is it wired to the headphone jack of the machine or this is a case of the chip supporting it, but not having it physically connected to anything inside? Anyone got SPDIF output working on their thinkpads? Does it need some expansion dock or something?

Thanks!


Edit: Corrected typo

[RealBlackStuff]

(apparently it also supports sound sound) ??
I've had (and still have) many T23s but never heard of SPDIF on them.
It's certainly not hardwired in a T23.
You can buy a PCMCIA sound card with S/PDIF, such as
http://www.pcmag.com/article2/0,2817,1746178,00.asp
Cheap on eBay as well... http://cgi.ebay.com/SB-AUDIGY2-ZS-NOTEB ... 0369782971

[UnixNut]

(apparently it also supports sound sound) ??

Hahaha sorry! typo. I meant surround sound

I've had (and still have) many T23s but never heard of SPDIF on them.
It's certainly not hardwired in a T23.
You can buy a PCMCIA sound card with S/PDIF, such as
http://www.pcmag.com/article2/0,2817,1746178,00.asp
Cheap on eBay as well... http://cgi.ebay.com/SB-AUDIGY2-ZS-NOTEB ... 0369782971

Indeed I can buy one (although they are rare where I am, I'm not in the US), but apart from being cheaper and recycling existing parts, this is fun for me. It's one thing to just buy a addon, it's another to mod what you have to provide a feature that wasn't originally provided, or a feature that was hidden but available, using parts that I already have.

I've spent a couple hours today hunting down the datasheets for the ICH Chipset and sound card, and it actually looks promising.

The T23 has an onboard Cirrus Logic CS4624-CQ sound chip. This is a low power version of the CS4622 desktop sound chip, usually used in mid-range PCI sound cards.

Now the CS4624-CQ sacrifices surround sound decoding for lower power consumption, so the T23 does not support surround sound, but it does support SPDIF Input and Output. Not only that, but it supports AC3 passthrough in addition to PCM data, so your Thinkpad can send surround sound data to a surround sound processor for decoding. Quite cool IMO.

From what I've gathered so far, the card will take SPDIF input for recording and will happily output either SPDIF AC3 or PCM from 48KHz samplerate downwards. This is provided from pins 83 and 84 on the sound chip.

I will have a go at getting this actually working, as this is all in theory, and I have no way of testing until I actually build a circuit interface and attach it to my DAC (as I lack a logic probe, or any kind of oscilloscope for that matter). Until I get some time to do this, I will put up some schematics of the interface circuit and a copy of the datasheet, for anyone else that might actually be interested in having a go themselves.

I can select SPDIF output on my machine, and it seems to open the card and play ok (I just can't hear anything), so it seems to work on the software side of things.


P.S Based on what I've studied so far, I suspect that other (IBM built?) Thinkpads also have SPDIF I/O (such as my X41) as they all seem to use similar Cirrus Logic chips, but this is just a suspicion for now.