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Subject: Re: audio line specifications
References: <3DEE2757.EE79B063@crf.canon.fr> <3DEFD744.3A2D8C8D@gv.net>
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Date: Fri, 06 Dec 2002 10:57:23 -0500
NNTP-Posting-Date: Fri, 06 Dec 2002 10:57:23 EST
Organization: Bell Sympatico
On Fri, 6 Dec 2002 05:28:57 -0800, Watson 'Atto Parsec' Name
>In article ,
>> "Michael R. Kesti" wrote in message
>> > Vlad wrote:
>> > >Yes. The impedance of the line is NOT important.
>> > The impedance of the line is not usually important, because audio lines
>> > are usually shorter than the shortest wavelength in the audio band.
>> ** Not again!! This is non relevant. If you need a ( twisted pair)
>> balanced audio line to have a flat response over distances of 100 metres or
>> more then correct termination of the line is important. If wavelength was
>> the issue then it would not matter until 10 or 15 km.
>I have read many of the followups, and I don't think anyone has
>mentioned the subject of the cable capacitance and why it is necessary
>to have a low enough impedance to prevent the cable capacitance from
>rolling off the high end of the signal. In other words, the line driver
>has to have a low enough impedance to drive the line adequately at the
>highest frequencies, no matter what the length of the line is. It could
>be only 3 meters long, but if the driver is a crystal microphone, which
>has a high impedance, then the high end may be rolled off by the few
>hundred pFs of cable capacitance.
>> ................. Phil
Yes you have
Read it again:
One of the few ...
One of the few advantages of the low impedance source is the improved
resiliency to cross-talk from adjacent lines. In most cases shielding
is not required for better than 70 db S/N
At list you aren't advocating that the line must be terminated at both
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