Subject: Re: [linux-audio-user] External DAC for mastering use?
From: Anahata (anahata_AT_treewind.co.uk)
Date: Tue Mar 23 2004 - 13:39:00 EET
On Tue, Mar 23, 2004 at 10:27:02AM +0000, Daniel James wrote:
> Currently its about 18 miles away, but I might convert a building in
> the garden for recording purposes. Do you know what the limitations
> on the length of S/PDIF cables are?
http://www.epanorama.net/documents/audio/spdif.html :
S/PDIF (IEC-958) uses 75 ohm coaxial cable and RCA connectors. 75 ohm
coaxial cable is inexpensive, because it is the same cable as used in
video transmission (you can buy a video cable with RCA connectors to
connect you S/PDIF equipments together). Coaxial S/PDIF connections work
typically at least to 10-15 meter distances with good 75 ohm coaxial
cable.
[Optical TOSLink]
Because high light signal attenuation in the Toslink fiberoptic cable,
the transmission distance available using this technique is less than 10
meters (with some equipments only few meters).
I wouldn't normally do your Googling for you, but I was quite interested
in the answer myself :-)
That link also mentions the AES/EBU standard, which uses the same
signal timing but higher levels and will therefore travel greater
distances: "AES/EBU signal transmission work for few tens of meters with a
good cable." - The cable has to have 110 ohm characteristic impedance.
I'm also interested in the possibility of feeding S/PDIF over structured
cabling using CAT 5 cable. Has any one tried this? I wonder how far it
would go with suitable impedance conversion. 50/75 ohm transformers
would also give electrical isolation.
-- Anahata anahata_AT_treewind.co.uk Tel: 01638 720444 http://www.treewind.co.uk Mob: 07976 263827
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