Date: Tue, 13 May 2014 20:31:18 +0200 From: Hans Petter Selasky <hps@selasky.org> To: freebsd-multimedia@FreeBSD.org Subject: OSS mains HUM filtering 50Hz / 60Hz ? Message-ID: <537264F6.5060808@selasky.org>
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Hi, Some of my USB audio headsets seems to be picking up mains HUM even if powered from battery. At first I thought the mains HUM came from the computer, but then I did some work and I verified my findings by sampling the AC network using a non-switching power supply. Maybe it does not belong in the FreeBSD audio stack, but I think it would be very clever to have a configurable band-reject filter in the FreeBSD DSP framework for 50 and 60Hz? Do we have such a filter mechanism already? Not sure if this is a so-called "feature" or not ... :-) http://en.wikipedia.org/wiki/Mains_hum http://www.selasky.org/hans_petter/hum.png --HPS
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