Before asking about digital audio: READ this Digital Audio Primer
Feb 21, 2009 at 2:50 AM Post #17 of 77
So I got to ask. If I2S protocol was designed for register and timing information transfer, why aren't manufacturers making it available on the ethernet bus for use with other digital devices (ie dacs/printers/cameras)?
 
Feb 21, 2009 at 2:59 AM Post #18 of 77
Quote:

Originally Posted by Happy Camper /img/forum/go_quote.gif
So I got to ask. If I2S protocol was designed for register and timing information transfer, why aren't manufacturers making it available on the ethernet bus for use with other digital devices (ie dacs/printers/cameras)?


because theres enough wrong with what you just said to make me cringe

ethernet isn't a bus, its a protocol standard that specifies not only a connection standard (physical layer) but a software/transmission layer as well

using I2S over 8P8C (the first person that "corrects" me saying RJ-45 is going to get slapped so hard their grandchildren will be born dizzy) is "non-standard" compliant, and EIA/IEEE/Intel/ASA/ISO/etc are pretty clear in terms of what their standards mean/do, and don't like non-standards crap happening when they can avoid it (in other words, yes, the law does matter quite a bit here)

then theres the bit that I2S doesn't do particularly well over long runs, which goes back to non-standard complaint, as ethernet over 8P8C is spec'd for roughly 100 meters transmission, I2S couldn't really do that same run, and so begins the standards issue (using the same connector for two standards often causes issues, for example cinch connectors)

the I2S standard is specified for audio, only, as an "inter-chip" connection, in other words its a bus protocol for "on board" communication

now, there are a few manufacturers and inventive modders who run I2S via 8P8C over Cat5E or Cat6 between devices, theres nothing inherently wrong with this, but they aren't running 100 meters+, and it can't be plugged into switching routers or similar equipment, and theres various other limitations, in other words, its kind of a hacked solution (and it works oh so well, and I mean this)
 
Feb 21, 2009 at 3:36 AM Post #19 of 77
An excellent thread. Thanks to the OP and to those adding to the discussion.
 
Feb 21, 2009 at 5:14 AM Post #20 of 77
Thank you for taking the time to give such an answer.

I am wondering why this bus communication protocol hasn't been used more since it's inception for external dac use.
 
Feb 21, 2009 at 5:55 AM Post #21 of 77
nick_charles
I'll be digging up the reason for the minimum length restrictions on S/PDIF this weekend.

obobskivich
Thanks, 10m for coax S/PDIF seems to be the max length.

elrod-tom
Thanks, want to sticky it?
smily_headphones1.gif


Happy Camper
Source to DAC using I2S really is a hacked solution using a protocol that wasn't designed for it. It's also not a perfect hack at that since DACs generally don't expect to deal with long wires.

The question of why more consumer products don't use it is similar to asking why use USB when you can hard-wire your CPU to interact with a certain device - there are consumer standards for interoperability, availability and usability and that's S/PDIF which is installed on most audio equipment.
 
Feb 21, 2009 at 6:03 AM Post #22 of 77
10 meters or 25 feet
wink.gif


haha

Happy Camper

its been around for a while, and its used A LOT, its inception was for internal use though, the example wiki gives is connecting a CD transport to a DAC inside of the enclosure (and likely on the same board), the example I'd give is Audigy 2 ZS connecting to its ADC and DAC, there are a ton of places where I2S is used, but its always short little board traces, or sometimes a ribbon cable
 
Feb 21, 2009 at 6:25 PM Post #25 of 77
The AES/EBU format is identical as far as I'm aware to SPDIF except for the higher voltage and obviously CMR.

It still seems crazy to me that some consumers want to spend a hundred times more than the top studios in the world, on largely irrelevant digital cable but don't seem to know or care about the most significant aspect of listening/monitoring, the listening environment. Can anyone explain this logic to me please?

FaleenAngel - "With analog, I still have no problems with driving a 10m long interconnect with a proper buffer". Not advised though and no professional would go longer than 5m as there is every likelyhood of interference. Bare in mind professionally we use mostly balanced, when we use unbalanced it is most commonly with a high Z output from say an electric guitar.

obobskivich - thanks.

G
 
Feb 22, 2009 at 12:08 AM Post #26 of 77
Quote:

Originally Posted by gregorio /img/forum/go_quote.gif
The AES/EBU format is identical as far as I'm aware to SPDIF except for the higher voltage and obviously CMR.


There is a slight difference in control bits sent, but otherwise identical, yes.

Quote:

Originally Posted by gregorio /img/forum/go_quote.gif
It still seems crazy to me that some consumers want to spend a hundred times more than the top studios in the world, on largely irrelevant digital cable but don't seem to know or care about the most significant aspect of listening/monitoring, the listening environment. Can anyone explain this logic to me please?


WAY off topic and scope, lets not go in this direction at all please.

Quote:

Originally Posted by gregorio /img/forum/go_quote.gif
FaleenAngel - "With analog, I still have no problems with driving a 10m long interconnect with a proper buffer". Not advised though and no professional would go longer than 5m as there is every likelyhood of interference. Bare in mind professionally we use mostly balanced, when we use unbalanced it is most commonly with a high Z output from say an electric guitar.


Makes sense, but this is getting into common practices vs design principles. Analog interconnects are also slightly out of scope of the article. Good to know for reference though, thanks.
 
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