Hi!
I'll need to transmit 8 ch of audio to a DAC, I'll be using a DICE to interface everything.
I can put SPDIF receivers inside the DAC box and run coax or optical cables.
Or I can run i2s, with a buffer chip (or symetrical line drivers?) for each signal. I'd like to run these lines in a sub-d.
Which one will lead to less jitter? What buffer to use for the i2s clock, a clock buffer? But won't there be too much time differences between data and clock? Do you know low jitter chips?
Thank you,
Nicolas
I'll need to transmit 8 ch of audio to a DAC, I'll be using a DICE to interface everything.
I can put SPDIF receivers inside the DAC box and run coax or optical cables.
Or I can run i2s, with a buffer chip (or symetrical line drivers?) for each signal. I'd like to run these lines in a sub-d.
Which one will lead to less jitter? What buffer to use for the i2s clock, a clock buffer? But won't there be too much time differences between data and clock? Do you know low jitter chips?
Thank you,
Nicolas
I'd use something like National's LVDS differential line driver family to send I2S, and you would use the same device across the board for data and all clocks. You need to choose a device with guaranteed device to device skew specifications. (A few nS would probably be ok)
Not really sure about your choice of connector. Something designed for a controlled impedance environment and high speeds would seem like a better choice. What that would be I have no idea. (yet..)
Not really sure about your choice of connector. Something designed for a controlled impedance environment and high speeds would seem like a better choice. What that would be I have no idea. (yet..)
phofman said:
Seems like a reasonable choice to me, cross-talk between the pairs could be a concern, but LVDS signaling should take care of that issue.
Thank you for your answers 🙂
Ethernet won't do the trick running balanced: I need to transmit 8 ch, so 4 i2s DATA + Frame clock + Bit clock.
Cables will be short, should not exceed 50cm.
I could use Ethernet unbalanced (there's only shielding), or use balanced connection on a hd sub-d 15...
I wish I would use some impedance specified cable/plugs, but I need to transmit 6 lines, and here lays the problem...
Ethernet won't do the trick running balanced: I need to transmit 8 ch, so 4 i2s DATA + Frame clock + Bit clock.
Cables will be short, should not exceed 50cm.
I could use Ethernet unbalanced (there's only shielding), or use balanced connection on a hd sub-d 15...
I wish I would use some impedance specified cable/plugs, but I need to transmit 6 lines, and here lays the problem...
NeoY2k said:
What's to prevent you from using several ethernet connectors? Balanced LVDS is really preferable to unbalanced, and standard I2S is not designed to be shipped long distances. (I'd say anything over about 5 cm without buffering.)
Thank you all 🙂
SCSI twisted pair and balanced LVDS should do the trick.
What about the jitter?
Thank you,
Nicolas
SCSI twisted pair and balanced LVDS should do the trick.
What about the jitter?
Thank you,
Nicolas
I use an RS423 driver and receiver for my I2S link and it works fine. I use cat 5 twisted pairs and 9 pin d type connectors over a metre or so and it works fine.
I believe balanced I2S is lower in jitter than SPDIF because of the difficulties caused in making SPDIF self-clocking, and (more importantly) the extraction of the clock at the receiver end.
I2S has none of that problem.
I suspect LVDS would be a better option, but it might be overkill. I recall professionally using LVDS to transmit DVB transport streams in parallel. So, that's 8 data lines and several clock signals in a bundle of twisted pairs running at about 8-10MHz quite happilly, over 10 metres or so (we didn't need to try any further).
I believe balanced I2S is lower in jitter than SPDIF because of the difficulties caused in making SPDIF self-clocking, and (more importantly) the extraction of the clock at the receiver end.
I2S has none of that problem.
I suspect LVDS would be a better option, but it might be overkill. I recall professionally using LVDS to transmit DVB transport streams in parallel. So, that's 8 data lines and several clock signals in a bundle of twisted pairs running at about 8-10MHz quite happilly, over 10 metres or so (we didn't need to try any further).
peufeu said:
Only possible issue with doing it that way would be skew between the clock, word clock and the data. (L/R clock is pretty slow so probably no problem here.) I haven't found I2S to be robust over any significant distance - admittedly my experience is limited.
I guess just try it and see what happens.. You can always fix it later if it does not quite live up to expectations.
Thank you peufeu 🙂
I'll have to check the cost of both solutions.
I don't think line drivers are expensive. I'll check.
SCSI connectors are just so expensive 🙁 but well...
I think I'll go with line drivers because these units will be used on stage - and who knows, if the lights guy puts his triacs near your sound rack...
Thanks
Nicolas
I'll have to check the cost of both solutions.
I don't think line drivers are expensive. I'll check.
SCSI connectors are just so expensive 🙁 but well...
I think I'll go with line drivers because these units will be used on stage - and who knows, if the lights guy puts his triacs near your sound rack...
Thanks
Nicolas
There are 8ch versions from Texas of LVDS line drivers, 150ps skew.
5$ the chip.
Let's take one driver, one receiver, small board to connect everything - really not a problem.
Unfortunately connectors and twisted pair SCSI is not the same price xD
5$ the chip.
Let's take one driver, one receiver, small board to connect everything - really not a problem.
Unfortunately connectors and twisted pair SCSI is not the same price xD
Use HDMI connectors then. Twisted pair, good for LVDS, and cheap...
Why don't you just put everything in the same box btw ?
Why don't you just put everything in the same box btw ?
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