Shielding a passive audio switchbox

oldschool · 2018-02-13T21:45:38+00:00

I picked up a passive audio switchbox. I intended to use it to switch the computer outputs going to a small stereo amplifier. In other words, I have this small bookshelf stereo, and I have three computers that I want to amplify the audio signal. One is my desktop computer which is intended to only be used for storage and playing music and videos. It is not connected to the internet. The second computer is the desktop that I use on the internet. The third is my laptop computer. For years I have been swapping plugs from computer to computer. And while that is not the biggest task, the cables always get tangled up and it's a small hassle. I thought I solved it when I bought this 4 button switchbox. It sas intended for audio and video. (Has the two RCA audio plugs Red/White, and the Yellow video plug). In this case I just do not use the yellow ones. This switchbox is nothing but a plastic box with four push button switches and corresponding inputs that go to one set of stereo outputs (RCA jacks) and the unused video ins and outs. There are no active electronics in the box. No power supply or semiconductors. The problem is that it picks up hum. The reason is obvious. The box is plastic and is not shielded. So while all the input and output cables are shielded, this box is not. Aside from buying another switchbox, or transferring all the components from this one into a metal box, I was wondering if I could simply coat the entire insides of this box with aluminum foil. Glue it to the box, and make sure it's bonded to the grounds (shielded part of the cable connectors). Will this work?

Feb 13, 2018 101 Replies

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jurb6006 8 years ago

previously. "

To my recollection you started it. Can you find the instance where I did ? Someone called me vulgar when I had no intention to be, so maybe you took something wrong.

If I did it, it is in there in the archived posts. If you show me and it is not something really stupidly thin skinned I will actually apologize. And I admit when I am proven wrong.

Or we could have a nice fun flame war until the coming of the Christ. (and I ain't religious at all)

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Phil Allison 8 years ago

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** No, it's not a ground lift switch at all.

Known either as "ground" or "polarity" switches, they were fitted to many guitar amps made in the USA until the end of the 1960s - plus a few even later on in case owners had to use a two pin outlet with an adaptor.

The switch was a changeover type with the two non moving contacts connected to active and neutral. The moving contact had a film cap strung between itself and chassis.

When the cap was switched to be between chassis and neutral, it reduced 60Hz noise quite a lot.

.... Phil

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