Here in Ohio wrote:
On 19 Nov 2006 15:49:13 GMT, Walt wrote
wrote:
Balanced inputs on audio equipment almost never have significant
common mode rejection at radio frequencies.
This is the first time I've ever heard anyone say this. Do you have
a cite?
My guess is that RFI will not be reduced by using a balanced input.
My guess is otherwise. Of course, I'm not really guessing.
Unless the RFI signal is predominantly positive or negative
(assymetrical), I would think that it would effect the + and - signal
and conductors in a balanced cable equally.
In theory, they are induced equally in the two conductors and are
removed when you take the difference. This is true regardless of the
symetry or non-symetry of the interference.
The differential input would then eliminate most of the RFI since it
is common to both legs of the signal path.
Yes. But conventional transistors/IC's reject common mode up to a
certain level, above that level they "break down" and no longer reject
common mode interference. Perhaps that is what normanstrong is alluding to?
Anyway, stubborn interference problems can be cured with a transformer,
which does not have a breakdown voltage.
//Walt