Re: How come, Steve? ...

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

In Reply to: How come, Steve? ... posted by andyr on October 26, 2004 at 22:32:10:

I had understood that a cable shield only acts as a shield (faraday cage) if it is connected (to earth) at one end or both ... if it floats, then it does not do any shielding? So, likewise a metal case?
I wasn't implying that there was anything "special" about an "earth ground" ... simply that if the case was not grounded, it wasn't doing a good shielding job.
I guess it's this whole use of the word "ground" that causes such confusion.
"Ground" doesn't just mean some rod stuck in the earth. It can mean that, but that's not the ground that's of relevance here. Here the relevant "gound" is the ideally singular point that the circuit in the chassis references.
And even that isn't necessarily of particular relevance with respect to a Faraday shield.
If the shield fully encloses the circuit, it needn't be connected to anything, even the circuit's reference ground as the fields within such an enclosure are ideally zero.
Of course such a perfect enclosure rarely exists in the real world and real world enclosures will have seams, holes and other discontinuities which reduce its effectiveness as a Faraday shield and in such cases connecting the shield to the circuit's reference ground (and not earth ground) helps to reduce capacitive coupling of interfering fields between the enclosure and the internal circuitry.
As far as the original poster goes, I'm sure his Marantz integrated amp is already properly grounded internally and using a three conductor power cord in order to tie its chassis to the AC safety ground won't do any good as far as shielding goes and will likely result in more noise by adding a ground loop that wasn't there to begin with.
se

This post is made possible by the generous support of people like you and our sponsors:

Schiit Audio

Follow Ups Full Thread

Topic - Add a ground wire to a two-wire amp? - Filbrik 17:05:28 10/26/04 (8)

Re: Add a ground wire to a two-wire amp? - Filbrik 13:01:29 10/27/04 (0)

Re: Add a ground wire to a two-wire amp? - andyr 18:05:05 10/26/04 (5)

Re: Add a ground wire to a two-wire amp? - cdb 19:14:57 10/27/04 (0)

Re: Add a ground wire to a two-wire amp? - Steve Eddy 20:53:10 10/26/04 (3)

How come, Steve? ... - andyr 22:32:10 10/26/04 (2)

Re: How come, Steve? ... - Steve Eddy 23:07:35 10/26/04 (1)

Thanks, Maestro! (nt) - andyr 23:34:16 10/26/04 (0)

Re: Add a ground wire to a two-wire amp? - Steve Eddy 17:44:58 10/26/04 (0)

Follow Ups

Re: How come, Steve? ... - Steve Eddy 23:07:35 10/26/04 (1)

Thanks, Maestro! (nt) - andyr 23:34:16 10/26/04 (0)

You can not post to an archived thread.