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Digital Interconnect to DAC, but once inside...
On 21 Oct 2005 05:45:38 GMT, wrote:
I have been surfing the 'net reading all kinds of info about digital
interconnects, and the general drift is that a digital interconnect
ideally needs to be constructed so as to maintain a nice, constant 75
ohm characteristic impedance, including the connectors (the connections
and connectors theoretically being the source of any transmission
problems).
That's correct in a qualitative sense, although seldom a quantitative
problem.
I understand that it is difficult to properly manufacture an RCA
connector for this application. Some sources (proponents of expensive
cables mainly) warn of dire consequenses if there are tiny
irregularities in the insulation/shield diameter, quality of the solder
joints, etc.
There will certainly be an impedance discontinuity, which will
introduce reflections. Whether that will disturb the datastream enough
to cause reading problems is much more arguable.
NOW... I reallize that there is controversy as to the real importance
and audiblity of all this stuff, but my question has to do with what
happens to the signal once the signal physically enters the DAC!
The Tri-Vista 21 uses the usual RCA coaxial connection at the input,
but the connection between the connector and the circuit board is a 5
inch long twisted pair of 22-gauge wires.
What effect (theoretically) does the change to the twisted pair have on
the characteristic impedance?
That depends on the impedance of that twisted pair - it may readily be
made to be 75 ohms by choosing wire with insulation of suitable
thickness.
Wouldn't the change from coaxial cable to twisted pair have more of an
effect on signal quality than the short length of "improper" shield
diameter going through an RCA connector?
Not necessarily, for the reason given.
--
Stewart Pinkerton | Music is Art - Audio is Engineering
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