How does a sound card set its anti-aliasing filters? After all, you can program a sound card to read at say 44.1kHz or 22,050Hz or half of that again so how do the ani-aliasing filters change? Switched cap filters are sampled filters so they would not be good and digital filters are no good either as we need analogue filters jus before sampling. Shytot
Sound Card Question
Started by ●August 23, 2005
Reply by ●August 23, 20052005-08-23
Typically, the sound card does the A/D conversion at a fixed sample rate (say 48kHz), and then the audio is re-sampled to the desired sample rate either by the sound card or by the OS. At least that is my understanding. So in effect, the anti-aliasing filters are digital. BTW, with modern oversampling ADCs, the anti-aliasing filters need not be very steep. The audio is sampled at a rate considerably higher than the eventual sample rate, so your anti-aliasing filters only have to cut-off frequencies higher than the oversampled Nyquist rate (100's of kHz often), not the "actual" Nyquist rate. Again, digital filters are used. -- Jon Harris SPAM blocker in place: Remove 99 (but leave 7) to reply "Shytot" <Shytot@yme.com> wrote in message news:orwOe.4893$iM2.495840@news.xtra.co.nz...> How does a sound card set its anti-aliasing filters? After all, you can > program a sound card to read at say 44.1kHz or 22,050Hz or half of that > again so how do the ani-aliasing filters change? Switched cap filters are > sampled filters so they would not be good and digital filters are no good > either as we need analogue filters jus before sampling. > > Shytot > >
