16 Mar
2014
16 Mar
'14
9:33 p.m.
And those very good brick wall filters _will_ have a
considerable group
delay.
? The only way they'll have any group delay is if they're hybrids
using a minimum phase section to save on gates. The linear phase
section is going to do the heavy lifting in any modern design... if
there's any AA filter at all. Once all the hash has all been shaped
into the >1MHz region, many designs don't bother anymore.
Despite the Pono and Meridian press releases, minimum
phase/"apodizing" AA filters are not actually desirable.
Monty
On Sun, Mar 16, 2014 at 2:39 PM, Gene Heskett <gheskett(a)wdtv.com> wrote:
> On Sunday 16 March 2014 14:25:14 Ralf Mardorf did opine:
>
>> On Sun, 2014-03-16 at 08:58 -0700, Len Ovens wrote:
>> > I would mix the project at 48k or 96k
>>
>> Why 96 KHz? 48 KHz doesn't cause any issues, but already provides best
>> sound quality.
>>
> That I think is a personal call Ralf, primarily because at 48 Khz, your
> anti-aliasing filters had better be very very good brick walls by the time
> you get above 24Khz in input content just for the aliasing control. And
> aliasing noise, once introduced, cannot be removed by any known math
> function that does not have precise knowledge of the phasing (aka group
> delay) of the original signal.
>
And those very good brick wall filters _will_ have a
considerable group
> delay. IMO doing the sampling at 240K, then doing a
weighted sum shift (5
> stage shift) to decimate the data down to 48K, should result in dropping
> the alias caused noise floor by several db. Just bring lots of expensive
> hardware to do that.
>
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>
> Cheers, Gene
> --
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
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>
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