Co-ax SPDIF digital out
 

In article ,
Mike wrote:
Better to use a 75 ohm cable, for instance RG-59 or television cables
(better small diameter like I401). Using a normal audio cable could not
work in some circumtances. (and I pay I401 0.50 eur/m at the hardware
store).

Any normal length phono cable will work ok - you might get in problems
with very long runs with audio co-ax, though.

--
*How do you tell when you run out of invisible ink? *

Dave Plowman London SW 12
RIP Acorn

Co-ax SPDIF digital out
 

"Jim Lesurf" wrote in message
...
Strictly speaking, the cable should have a 75 Ohm characteristic
impedance,
and many phono leads intended for analog interconnects won't have this
impedance. That said, provided the cable is short (metre or so) this is
unlikely to give a problem.

Strictly speaking the connectors should be 75 Ohm as well - which is a bit
of a problem since most use phono connections and there is no such thing as
a 75 Ohm phono plug.

In fact I think that this is one case where a cheap analogue cable is likely
to be better than some of the more expensive ones. The exotic audio cables
have weird and wonderful geometries that may well introduce more capacitance
and/or inductance into the signal. That might be fine at audio frequencies
but could do nasty things to a digital signal.

For peace of mind, though, I tend to recommend using a length of 75 Ohm
co-ax of one of the types usually sold for TV and VHF antenna leads. Of
course, not all such leads *will* be 75 Ohm at frequencies below a MHz..
;- So this comes back to "probably doesn't matter much" in most domestic
situations.

Probably doesn't matter much but you are best to have a cable that is 75 Ohm
well into the MHz range, although I guess that the fundamental signal is
only in the range of about 1 MHz, a square wave consists of all the odd
harmonics of the signal (IIRC) and so goes well up the scale.

Co-ax SPDIF digital out
 

"Jim Lesurf" wrote in message
...
Strictly speaking, the cable should have a 75 Ohm characteristic
impedance,
and many phono leads intended for analog interconnects won't have this
impedance. That said, provided the cable is short (metre or so) this is
unlikely to give a problem.

Strictly speaking the connectors should be 75 Ohm as well - which is a bit
of a problem since most use phono connections and there is no such thing as
a 75 Ohm phono plug.

In fact I think that this is one case where a cheap analogue cable is likely
to be better than some of the more expensive ones. The exotic audio cables
have weird and wonderful geometries that may well introduce more capacitance
and/or inductance into the signal. That might be fine at audio frequencies
but could do nasty things to a digital signal.

For peace of mind, though, I tend to recommend using a length of 75 Ohm
co-ax of one of the types usually sold for TV and VHF antenna leads. Of
course, not all such leads *will* be 75 Ohm at frequencies below a MHz..
;- So this comes back to "probably doesn't matter much" in most domestic
situations.

Probably doesn't matter much but you are best to have a cable that is 75 Ohm
well into the MHz range, although I guess that the fundamental signal is
only in the range of about 1 MHz, a square wave consists of all the odd
harmonics of the signal (IIRC) and so goes well up the scale.

Co-ax SPDIF digital out
 

In article , "Bedouin"
bedouin@yonderblue wrote:
"Jim Lesurf" wrote in message
...
Strictly speaking, the cable should have a 75 Ohm characteristic
impedance,
and many phono leads intended for analog interconnects won't have this
impedance. That said, provided the cable is short (metre or so) this
is unlikely to give a problem.

Strictly speaking the connectors should be 75 Ohm as well - which is a
bit of a problem since most use phono connections and there is no such
thing as a 75 Ohm phono plug.

Indeed. ;-


For peace of mind, though, I tend to recommend using a length of 75
Ohm co-ax of one of the types usually sold for TV and VHF antenna
leads. Of course, not all such leads *will* be 75 Ohm at frequencies
below a MHz.. ;- So this comes back to "probably doesn't matter
much" in most domestic situations.

Probably doesn't matter much but you are best to have a cable that is 75
Ohm well into the MHz range, although I guess that the fundamental
signal is only in the range of about 1 MHz, a square wave consists of
all the odd harmonics of the signal (IIRC) and so goes well up the scale.

In principle, losing some of the 'squareness' of the edges should not
matter if the receiver can still read the data OK. Although there may be a
possible effect of 'data induced jitter' of the kind that Julian Dunn and
others have discussed in the past. In practice I have my doubts about this
being a serious problem, though, in most casts.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Co-ax SPDIF digital out
 

In article , "Bedouin"
bedouin@yonderblue wrote:
"Jim Lesurf" wrote in message
...
Strictly speaking, the cable should have a 75 Ohm characteristic
impedance,
and many phono leads intended for analog interconnects won't have this
impedance. That said, provided the cable is short (metre or so) this
is unlikely to give a problem.

Strictly speaking the connectors should be 75 Ohm as well - which is a
bit of a problem since most use phono connections and there is no such
thing as a 75 Ohm phono plug.

Indeed. ;-


For peace of mind, though, I tend to recommend using a length of 75
Ohm co-ax of one of the types usually sold for TV and VHF antenna
leads. Of course, not all such leads *will* be 75 Ohm at frequencies
below a MHz.. ;- So this comes back to "probably doesn't matter
much" in most domestic situations.

Probably doesn't matter much but you are best to have a cable that is 75
Ohm well into the MHz range, although I guess that the fundamental
signal is only in the range of about 1 MHz, a square wave consists of
all the odd harmonics of the signal (IIRC) and so goes well up the scale.

In principle, losing some of the 'squareness' of the edges should not
matter if the receiver can still read the data OK. Although there may be a
possible effect of 'data induced jitter' of the kind that Julian Dunn and
others have discussed in the past. In practice I have my doubts about this
being a serious problem, though, in most casts.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Co-ax SPDIF digital out
 

In article , Jim H
wrote:
more from the 'Jim Lesurf school' of uk.rec.audio-ism:


Strictly speaking, the cable should have a 75 Ohm characteristic
impedance, and many phono leads intended for analog interconnects
won't have this impedance. That said, provided the cable is short
(metre or so) this is unlikely to give a problem.

I've never experianced any problems using them interchangeably, possibly
because some of my 'analog' cables are 75Ohm. Could this cause problems?

Pretty unlikely to cause problems with leads only a metre or two in length.
However if mis-matched, the longer the run, the more effect this may have
upon the shapes of the data waveforms and how much the transmitter might be
upset by having to drive an incorrect load.

I've cheerfully used 50 Ohm co-ax and also 'randomly chosen' phono-coax for
short lengths, and it seemed fine. However this was for lengths of 1 metre,
and with Meridian DACs at the receiving end. These seem to be good at
rejecting various problems. Hence I suppose it is possible that some
combinations of 'odd' cable and transmitter/receiver would be problematic.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Co-ax SPDIF digital out
 

In article , Jim H
wrote:
more from the 'Jim Lesurf school' of uk.rec.audio-ism:


Strictly speaking, the cable should have a 75 Ohm characteristic
impedance, and many phono leads intended for analog interconnects
won't have this impedance. That said, provided the cable is short
(metre or so) this is unlikely to give a problem.

I've never experianced any problems using them interchangeably, possibly
because some of my 'analog' cables are 75Ohm. Could this cause problems?

Pretty unlikely to cause problems with leads only a metre or two in length.
However if mis-matched, the longer the run, the more effect this may have
upon the shapes of the data waveforms and how much the transmitter might be
upset by having to drive an incorrect load.

I've cheerfully used 50 Ohm co-ax and also 'randomly chosen' phono-coax for
short lengths, and it seemed fine. However this was for lengths of 1 metre,
and with Meridian DACs at the receiving end. These seem to be good at
rejecting various problems. Hence I suppose it is possible that some
combinations of 'odd' cable and transmitter/receiver would be problematic.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Co-ax SPDIF digital out
 

"RJH" wrote in message ...

I've used 10 metres of normal phono cable - seemed to work fine. What's
'lost' then, according to the manufacturers of these digital link cables?

Rob

The signal amplitude will degrade a little over distance as will the
sharpness of the edges of the digital signal. Any decent SPDIF
receiver in a properly designed product will sort this out. (Therein
lies the problem.)

Co-ax SPDIF digital out
 

"RJH" wrote in message ...

I've used 10 metres of normal phono cable - seemed to work fine. What's
'lost' then, according to the manufacturers of these digital link cables?

Rob

The signal amplitude will degrade a little over distance as will the
sharpness of the edges of the digital signal. Any decent SPDIF
receiver in a properly designed product will sort this out. (Therein
lies the problem.)

Co-ax SPDIF digital out
 

"Jim Lesurf" wrote in message



I've cheerfully used 50 Ohm co-ax and also 'randomly chosen'
phono-coax for short lengths, and it seemed fine. However this was
for lengths of 1 metre, and with Meridian DACs at the receiving end.
These seem to be good at rejecting various problems. Hence I suppose
it is possible that some combinations of 'odd' cable and
transmitter/receiver would be problematic.

I've used a piece of zip cord with RCA plugs soldered at each end. I've read
a report of a guy who used two wetted fingers to make the connection between
a digital source and a digital converter.