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Correct connection of cable shields within an amp chassis?
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Author:  FenderBender [ 30 Jan 2013, 15:54 ]
Post subject:  Correct connection of cable shields within an amp chassis?

Hello everyone,

My chipamp (LM3886 x 2 + LM4780 (sub)) has been going strong for about a year now. I've always had a few quirks with it though. I ran out of wire when I did the initial build so I used some really old cheap and nasty unshielded twisted pair wire for the signal. Probably not the best of ideas. I've also been getting a little buzzing on high frequencies on one of the channels.

So I bought some wire from Markertek. I got some good quality Mogami stuff and I am going to rewire the parts I skimped on.

My question is: For each wire run between different components do you attach the wires shield to ground on just the "input" side. For example, my signal comes from 2 RCA jacks to a 4PDT switch (to headphone amp and to power amp), then to subwoofer crossover board. I run wire from the crossover's INPUT terminals(where I just inserted the wire, not on the crossover's output) to the Left and Right channel amp.

So the main wire runs are RCA --> Switch --> Subwoofer crossover --> Left and Right channel.

If you didn't get what I meant with the input terminals and subwoofer thing, I'm essentially just using the input terminals to splice the wire so that I can have the signal go to the subwoofer board AND to the left and right channel.

Here's a partial drawing. Where do the cable shield grounds get attached?

Author:  duncan2 [ 01 May 2013, 16:34 ]
Post subject:  Re: Correct connection of cable shields within an amp chassi

I take it that the 2 RCA sockets are insulated from the chassis?[NOT earthed to chassis] Then if there is an incoming earth from them then yes as you have shown the shields would be attached to the earth side of the RCA sockets this is to keep-radiated interference reaching the earth side of the cable
In all cases there should be no earth loops-therefore only ONE piece of equipment should have a mains earth. and that should be used for all the rest of the equipment. If possible star earthing should be used for ALL connections to the chassis .

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