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Old 17th Nov 2019, 5:04 pm   #1
Sparks
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Default Racal-Amplivox magnetic microphone screens

Quite often, used Astrolite headsets would arrive with screens installed in the boom, around the microphone. The product literature from decades ago described these screens as Mu-metal, whatever that means. Did they have any useful or actual purpose ? Thankyou.
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Old 17th Nov 2019, 5:45 pm   #2
Andrew2
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Default Re: Racal-Amplivox magnetic microphone screens

Possibly to reduce 'buzz' levels if the mic was to be used near something like a TV/computer monitor?
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Old 17th Nov 2019, 5:54 pm   #3
G6Tanuki
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Default Re: Racal-Amplivox magnetic microphone screens

Yes, the big CRT displays once used for military/ATC RADAR could deliver quite a nasty amount of magnetic 'buzz' from their scan-coils.
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Old 17th Nov 2019, 6:55 pm   #4
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Default Re: Racal-Amplivox magnetic microphone screens

Yes, Mu Metal is the stuff that was used as magentic screening for CRTs in scopes etc, as well as around small-signal audio transformers.

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Old 17th Nov 2019, 10:05 pm   #5
Sparks
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Default Re: Racal-Amplivox magnetic microphone screens

Thanks all. These headsets were used extensively by British Airways many years ago in the TriStar, Trident and Concorde fleets. Perhaps there were some cockpit instruments that didn't care for magnetic microphones.
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