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R/E/P => R/E/P Archives => Dan Lavry => Topic started by: twilightsong on November 17, 2005, 08:40:53 PM

Title: One more question regarding sampling
Post by: twilightsong on November 17, 2005, 08:40:53 PM
With regard to higher SR, what about:

>the transition band's effect on on the filtering process? Won't very high SR help alleviate this

>Isn't the bias freq of a good tape machine about 400khz? Doesn't this translate in some way to higher SR?

>isn't inter-modulation distortion easier to deal with using very high SR?

Am I a COMPLETE noob?

I'd appreciate feed back on these which came to mind (some of which I've been told or read over the years)

I'd did try a search, found nothing

Title: Re: One more question regarding sampling
Post by: Jon Hodgson on November 18, 2005, 05:09:14 AM
a 48kHz 128x oversampling converter actually does the A/D conversion at a 6.144 MHz, which allows the first analogue filter to be way above the audible band, and gentle enough that it produces effectively no ripple or phase shift in the audible band.

The subsequent downsampling (which reduces sample frequency but increases word length) includes additional filters, but since these are digital they can be made linear phase. There is a cost/performance thing here, since better digital filters need more taps and so take more silicon space (therefore cost), which is why some manufacturers of high end ADC boxes will use a converter chip which allows the sample stream to be read when it is still say 16x oversampled, and do the final stages using their own DSP code.