Twisted pair or Coax,which might be better?

[Mark7]

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Guest : A twisted shielded pair is designed for use in a balanced line with either a transformer or differential amplifier input.
Its advantage is with low level signals in a high noise environment:  the differential input cancels common mode signals. But, you cannot just change cable types and gain anything. The design of a balanced line over single ended circuitry is more exotic and costly.

Example : computer networking uses balanced lines as they link  systems connected to different power lines and usually have AC common mode voltage variations or even high level noise transients on  them. The balanced lines cancel this..........

So with single ended circuitry there is absolutely no benifit between a coax and a twisted pair?</font>

 

[Guest]

<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">So with single ended circuitry there is absolutely no benifit between a coax and a twisted pair?</td></tr></table>



Analog audio inputs normally have a high impedance and outputs very low - so they are not matched in the first place... Thus, If you are just working in the analog audio range, you can use a twisted pair - in fact, some audio cable does this to reduce cable capacitance. The 20KHz  and below is not as susceptible to impedance mismatch - large capacitance in long cable runs can be a significant cause of freq loss in this case. But,Having the center conductor less shielded by the grounded outer may cause hum  or noise pickup......


But, if you are working at video frequencies or with digital signals, you'd be better off staying with the norm to prevent reflections at the impedance discontinuities. In this case, inputs and outputs of the components are designed to have a 75 ohm Z.

Best.  

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