In Reply to: RE: The newer Wolfson DACs offer linear and minimum phase settings posted by Charles Hansen on February 10, 2009 at 00:41:13:
... about different filters for different sample rates. I was just pointing out that some of the popular DACs like the Wolfson do have different filters for different rates, in this case there are 3 bands with 5 filter selections for each (though only 3 filters are available for each in hardware control mode). Not meant to imply it's a replacement for a well implemented approach such as yours, but a sign that for the last few years the digital audio world maybe hasn't been quite as dire as some believe :)
Like you say, in the 2005 AES paper they do talk some about the available filter options and some of the reasoning behind the choices ...
AES 119th Convention, New York, New York, 2005 October 7–10, Page 4 of 10
2.7. Interpolation filters for 44.1kHz and 48kHz audio
Since there is no definitive indication that minimum
phase filters sound better than linear phase filters,
particularly given the phase distortion over the audio
band it was decided to implement a series of filters and
allow the end user to decide which filters to use. The
reduced latency of the minimum phase filters may be
ideal for studio situations where a low latency is needed.
Conversely some users may prefer the standard linear
phase filters.
The filters we chose to implement are:
1. linear phase
2. minimum phase with tailored response
3. minimum phase
4. no-alias linear phase
5. no-alias minimum phase
3.1.1. Interpolation filters for high sample rate audio
For the higher sample rates we settled on 5 filters
1. linear phase ‘soft knee filter’
2. minimum phase ‘soft knee filter’
3. linear phase brickwall filter
4. minimum phase apodising filter
5. linear phase apodising filter
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Follow Ups
- Sure, but it was mainly to John's comment ... - Slider 10:10:09 02/10/09 (14)
- RE: Sure, but it was mainly to John's comment ... - Charles Hansen 11:00:27 02/10/09 (13)
- Cambridge and Onkyo are using them - Slider 11:25:59 02/10/09 (12)
- RE: Cambridge and Onkyo are using them - Charles Hansen 14:05:28 02/10/09 (11)
- you may be right about the 8740 - Slider 20:46:14 02/10/09 (0)
- RE: Cambridge and Onkyo are using them - andy_c 16:17:00 02/10/09 (9)
- Thanks for the link - Charles Hansen 22:51:44 02/10/09 (8)
- Guys the filters are bypassed in the Wolfson - Gordon Rankin 07:45:23 02/11/09 (0)
- RE: Thanks for the link - andy_c 04:48:06 02/11/09 (0)
- RE: Thanks for the link - Todd Krieger 00:32:25 02/11/09 (5)
- Not What I Thought...... - Todd Krieger 01:35:51 02/11/09 (4)
- Like we said above, the Wolfson digital filter isn't used with the DacMagic - Slider 09:26:23 02/11/09 (3)
- Well, That Makes Sense...... - Todd Krieger 11:31:54 02/11/09 (2)
- Upsampling would be part of the DSP code - Slider 11:51:53 02/11/09 (1)
- RE: Upsampling would be part of the DSP code - Charles Hansen 12:38:47 02/11/09 (0)