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In Reply to: Re: SCD-1: Don't forget those filters! [long] posted by JCS on December 28, 2004 at 02:59:29:
Could you tell us what the differences (technically speaking) between these two interpolation filters are?
Normally the standard red book filtering is AFAK symmetrical with a sharp cut-off ("brickwall") to prevent Nyquist imaging, but with long energy smear. Does your Sony manual say anthing about these parameters?
Follow Ups:
If you want to know more about the red book filters on the SCD-1 (& the SCD-777ES of course) have a look at the Stereophile web site (http://www.stereophile.com/). In the Archives section under Digital Sources there is a review of the Sony SCD-1. It includes a detailed description of the different filters plus some frequency response plots.
Not sure how technical this will be, but I can relate what the manual says.
Sony uses what it calls a Variable Coefficient filter which alters the frequency roll-off from sharp to slow. The Standard setting uses the sharp roll-off and filters 1 through 4 use different implementations of the slow-roll off." Sharp roll-off filters quickly cut off noise over 22.05 kHz generated during sampling. On the other hand, slow roll-off filters cut off noise generated during sampling, and are able to hold pre-ringing and post-ringing (a kind of sound smearing) in the impulse response signal to a minimum."
As you can see they (Sony) have not really provided any technical info as to their algorithm construction.
Thanks, JCS. This confirms my presumption these Sony filters look very much like the first 4 in my dCS Delius DAC. These are symmetrical filters. For more information of the significance of filter characteristics on sound quality dCS has published some interesting Technical Papers on their website: http://www.dcsltd.co.uk/
BTW: I fully agree you better listen for longer periods of time to assess the impact of different filter settings. In my set I prefer the assymentrical filter 6 since my transport has been modified (increasing transparancy in a dramatic way). Before that I mostly used 2 or 3.
(nt)
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