This question came in from CE Pro reader Scott Hetzel of Pro Circuit AV in California.  Can anyone help him out?

“Some techs think its OK to send analog line level audio on digital coax.  Is there signal degradation in doing so?  Will the audio signal suffer doing this?  Is this acceptable?  I was taught that it is not the right way of doing this type connection.  I would love to get some engineering feedback.”

I don’t have eng data off hand, but personal exp I have used analog audio for Coax digital and Coax digital cables for analog… at the end of teh day they are the same cable.

Jason Knott - 13 August 2012 05:14 AM

This question came in from CE Pro reader Scott Hetzel of Pro Circuit AV in California.  Can anyone help him out?

“Some techs think its OK to send analog line level audio on digital coax.  Is there signal degradation in doing so?  Will the audio signal suffer doing this?  Is this acceptable?  I was taught that it is not the right way of doing this type connection.  I would love to get some engineering feedback.”

Yes, many pre-made interconnects that you purchase are of coaxial design as well.  But, it is very important to use “digital coax” or “serial coax” for this purpose because you need a coax with a solid bare copper (BC) center conductor and a 95% tinned copper braid for proper signal.  It is a bit more expensive than Cable TV coax, but pro installers have been using this type of coax for custom interconnects for years.

Note that standard CATV coax should never be used which is made of Copper-clad steel (CCS) center conductor and a 40 or 60% aluminum braid because it offers poor resistance for the audio signal.

Best,

Carl

RG6 coax is designed to attenuate frequencies below 50 Khz to reject interference. It should never be used for analog audio, ESPECIALLY for subwoofers. There is a significant loss of frequency response and signal amplitude versus the use of high impedence cable designed for audio. Digital coax cable is fine for a digital audio connection, but should not be used for analog.

There are two types of cable used for AV interconnects; coax and twisted pair.  Coax is generally recommended for use in video and digital audio applications while twisted pair is generally used for analog audio. Coax cables can be substituted for twisted pair in analog audio but twisted pair cannot be substituted for digital audio since digital audio requires 75Ohm cable.

The performance difference between coax and twisted pair for analog audio negligible.  Any differences in audio performance is far beyond the range of the human ear.

I don’t have eng data off hand