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General Asylum General audio topics that don't fit into specific categories. |
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General Asylum General audio topics that don't fit into specific categories. |
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In Reply to: Re: Some thoughts on filters posted by Charles Hansen on April 22, 2004 at 09:33:43:
> The basic problem is that the sample rate chosen for CD is too low.
Amen to that Charles.
> After looking at this issue for years, I think the only way to get
> great sound from digital is to sample at least 10x the highest
> frequency of interest. In this way, *no* low pass filter is needed,
> either for recording or for playback.
Of course, this is what was originally promised for DSD. But in
practise....
> The problem is that there are many knuckleheads on the pro side of
> things that put far too much faith in specs. So they add brickwall
> filters to their high sample rate equipment in order to achieve the
> best "numbers", even though it limits the sound quality.
The dCS converters I use for the Stereophile recordings offer a choice
of antialiasing filters. Even running at 88.2kHz, with choral and
piano sources, which don't have significant energy above the
traditional audioband, I feel the "slow" filters do sound better. But
then I have to low-pass filter _again_ to produce the CD. :-(> it seems like a contradiction to me that you would accept
> out-of-band energy when done in the downsampling process before
> the CD is made, and yet decry it when it happens in the playback
> DAC.
It does seem a contradiction, yes. I did some experiments on this
some years back, by feeding a transient into an ADC, looking at the
resultant data, then feeding those data to an oversampling DAC and
examining the waveform. The _big_ change, where every transient is
replaced by a sin x/x function, happens at the ADC (see your argument
above about high-sample-rate, non-LPF systems). The DAC/OS filter
added a little more of the same when it reconstructed the analog
waveform, but the difference was minor, I thought.
> I haven't personally tried a non-OS playback system (yet), but to
> dismiss it out of hand seems unwise to me. There are as many
> rational arguments in its favor as against it. The final factor of
> merit is how it sounds. I would be very curious to see a full
> review (including measurements) in Stereophile.
As I wrote in another posting this morning, while the magazine hasn't
formally reviewed an Audio Note DAC, we did review a minimal design
from 47 Lab review that does not have _any_ filter. See
http://www.stereophile.com/digitalsourcereviews/800/index5.html
for my measurements. Now, the 47 Lab DAC has other peculiarities that
may well affect its measured performance. But if you look at its
test results, you might be able to empathize with, if not agree with,
my skepticism. :-)
John Atkinson
Editor, Stereophile
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Follow Ups
- Re: Some thoughts on filters - John Atkinson 04/22/0410:38:01 04/22/04 (1)
- Re: Some thoughts on filters - Peter Qvortrup 03:22:21 04/24/04 (0)
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