shielded cables in enclosure

[jewilson]

Billy,

You can connect both end to ground, however it has proven fact that only one end is needed for audio. If you connect one end of the shield to gnd and the other end to gnd with a cap you can introduce AC current noise currents into the shield.

All of this depend on the frequency of inside your. However realize that once your connected to a part, or the PCB you have no shielding, then your dependent on the layout.

 

[maylar]

What if you used a shielded cable with two inner conductors? The inner conductors would carry signal and signal gnd, the shield can then be connected to chassis gnd or whatever.

In single-ended circuits the 2nd conductor would be redundant, since it would be ground anyway.

 

[Christer]

In single-ended circuits the 2nd conductor would be redundant, since it would be ground anyway.

I think traderbam meant to connect the shield only at one single
point, for instance one of the ends. At least that is what I assumed
in my follow-up post.

 

[jewilson]

Connecting the shielding at one end is done for audio frequencies and normally done at the source. However, you might find that it will sound different when connected the other way. You do not want noise currents flowing through the shield.

Shielding for high frequencies RF you connect the shielding at one end.

Shielding from Magnetic interference is done differently. You would use a shielded twisted pair, however the connection methods is are not stright forward.

 

[slowhands]

Within a chassis, for low level inputs like phono or mic, I ground a shield or twisted pair ground at only one end, the amplifier input. If you ground at both ends, you have ground loops. I do connect the incoming ground to chassis, but via a small reslstor to chassis ground to break ground loops.

Balanced inputs would be far better, but they are typically not an option for consumer audio equipment. The phono cartridge or mic is already unbalanced.

 

[jewilson]

Let me correctly my self. when transmitting RF signals the shield must be connected at both ends.

You should check out the book NISE REDUCTION TECHNIQUES IN ELECTRONIC SYSTEMS by OTT. All the good stuff is in this book.