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Using the I2S bus

gamma3, gamma24 (plug-in for the γ3)

Using the I2S bus

Postby Balcmeg » May 4th, 2017, 9:46 pm

Hi, Just a thought experiment so far, dont know if I will bother trying it out.

I saw the previous thread about using a raspberry Pi to make Gamma3 as a streamer - more or less what i am doing now but i keep them in separate enclosures and run the audio through USB with the widget and it works fine. Had to upgrade from my CuBox to am RPi 3 ko keep up with times (software).

Anyway, I did harbour some thoughts of using the RPi own I2S and put that right into Gamma3s I2S but Im not really certain as of how much the sound might still get processed inside the RPi, and how much tweaking would be needed of the software, so ill probably skip that part.

This did get me remembering that my Hardware streamer does have an RJ45 port for its own I2S signal out. As I understand things, it should be "fairly easy" (famous last words) to just remove the Widget and plug in wires to test how well this works out. Before I even start considering it, I'd like to hear from you here if it is even worth contemplating, as I understand it the I2S bus is not really suited for more than maybe 10cm long conductors and I guess Id have to use around 20cm if the unites are placed side by side. The streamer is pretty good though, so I figure that depending on architecture, going straight through I2S MIGHT be a step in the right direction since it should remove a bit of extra circuitry on the way of the signal to the Gamma24.

Any thoughts? Suggestions?

/Stefan
/Stefan
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Re: Using the I2S bus

Postby amb » May 5th, 2017, 3:19 am

I2S stands for "inter-IC sound" or "integrated interchip sound", which implies that it's for connection between chips on a board, or at least over very short distances. Line impedance and reflections are concerns as well. It is not meant for use as interconnection between chassis across a long cable.

USB, on the other hand, is designed for external interconnection, and with a good asynchronous transfer mode USB-I2S bridge such as the ζ1 audio widget, you get excellent jitter rejection characteristics. You might think that the extra electronics and processing by the ζ1 might degrade the performance, but in fact the opposite is true.
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Re: Using the I2S bus

Postby Balcmeg » May 5th, 2017, 4:34 am

amb wrote:I2C stands for "inter-IC sound" or "integrated interchip sound", which implies that it's for connection between chips on a board, or at least over very short distances. Line impedance and reflections are concerns as well. It is not meant for use as interconnection between chassis across a long cable.

USB, on the other hand, is designed for external interconnection, and with a good asynchronous transfer mode USB-I2S bridge such as the ζ1 audio widget, you get excellent jitter rejection characteristics. You might think that the extra electronics and processing by the ζ1 might degrade the performance, but in fact the opposite is true.


Thanks Ti,
This is more or less what I was thinking, but not sure of since the source have been unverified pages on the net. Hiowever, I don't know if the RPi support asynchronous transfer, but that might not be the most important issue.
I will research that, and planning a listening test where I compare the RPi + USB connection to Audio Widget with the streamer and its BNC output. Im letting my wife in on this test since she has been proven to have more critical hearing than me and less invested in wish *should be best*. Actually she is uninterested in technology, but enjoy the better sound. ;)
Although she does have an issue with BIG speakers or amps..
/Stefan
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Re: Using the I2S bus

Postby SonusBonum » May 5th, 2017, 6:16 am

Hi Stefan, not a bad idea at all...! I just discussed the same thing with my friend and DAC designer Cees Ruitenberg, owner of Metrum Acoustics. While he has designed his own ladder chip and implements it in his various DAC's he is able to "take" I2S directly from a I2S source, like the RPi. The interesting thing however is, like Ti suggests: "IS IT BETTER"...? I think it can be, as long as there's a good sync between the source and the destination, which means both clocks have to be synchronised. I mean, it has worked for decades in an ordinary CD player, why shouldn't it work in a FLAC/WAV/MP3 or whatever player...? Let me assure you, if I find or hear anything from that direction I will let you know in this thread... Greetz, Ronald
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