|
Digital Drive: RE: Theory vs. Real World........ by Werner Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
For Sale Ads |
217.136.59.109
In Reply to: Theory vs. Real World........ posted by Todd Krieger on July 6, 2009 at 08:52:36:
"The non-presence of pre-ringing with a linear-phase filter is impossible...."Ah, Todd, you still haven't read and understood Shannon's proof, right?
Actually I wanted to waste this evening's time on something else, but OK, here goes ...
This posting contains graphs taken from an audio editor. The dots represent actual sample values in a digital audio stream. **please disregard the continuous lines between the dots as these are generated by the editor's
display routing and are not part of the actual signal stream**.Let's start with the type of digital, linear phase, FIR filter as typically found in a commercial oversampling / reconstruction filter for CD replay. To keep the graphs manageable it is a 2 x oversampling filter, but as so many commercial silicon implementations it is half-band, i.e. any second coefficient is zero and the attenuation at Fs/2 is 6dB.
This is a particularly popular (because cheap) appromixation of the Sinc
reconstructor prescribed by Shannon and his ilk, and despised by Krieger and his followers (if any). Note the abundant pre- and post-ringing.--
The second graph is that of an analogue-origin impulse, as it would exist in a 44.1kHz sampled signal space after correct band-limiting (as per Shannon's requirement) and sampling. (This impulse was generated by making a single-sample positive impulse in a digital signal space with an obscenely high sampling rate, followed by very steep minimum-phase low-pass filtering with a very narrow transition band and subsequent decimation to 44.1kHz.)
Notice the absence of pre-ringing and the wide spectrum occupied in the
44.1kHz space.The relevance of this signal is that this is the fastest analogue-domain
band-limited event without pre-ringing that can be sampled with a 44.1kHz system. If this signal does not trigger pre-ringing upon playback and reconstruction then no signal will.--
--The third graph is what one gets when the above band-limited impulse signal is replayed at 44.1kHz but with 2 x oversampling and reconstruction with the initially presented half-band Sinc filter.
Now where has the Sinc's pre-ringing gone?
I did not invent this.
This post is made possible by the generous support of people like you and our sponsors:
Topic - What is wrong with digital-TAS Meridian CD & Speaker reviews - ruxtonvet 14:12:39 07/4/09 ( 44)
- bushinternet.com - abunke 14:05:51 07/24/09 ( 0)
Forgive my potential ignorance... - Gag Halfrunt 02:20:16 07/10/09 ( 2)
- RE: Forgive my potential ignorance... - Charles Hansen 00:03:43 07/14/09 ( 1)
- RE: Forgive my potential ignorance... - Gag Halfrunt 02:36:22 07/15/09 ( 0)
Tread carefully - Des 07:20:08 07/7/09 ( 0)
RE: What is wrong with digital-TAS Meridian CD & Speaker reviews - chris.redmond2@bushinternet.com 17:12:51 07/4/09 ( 32)
- RE: What is wrong with digital-TAS Meridian CD & Speaker reviews - Werner 01:10:24 07/5/09 ( 31)
- No, there are others. - Charles Hansen 14:49:47 07/5/09 ( 9)
- RE: No, there are others. - Spendor Harbeth 18:29:31 07/12/09 ( 8)
- RE: No, there are others. - Charles Hansen 23:59:44 07/13/09 ( 7)
- RE: No, there are others. - Spendor Harbeth 07:30:43 07/14/09 ( 6)
- RE: No, there are others. - Werner 02:53:13 07/15/09 ( 5)
- RE: No, there are others. - Spendor Harbeth 08:08:35 07/15/09 ( 4)
- RE: No, there are others. - Spendor Harbeth 19:57:21 07/16/09 ( 0)
- RE: No, there are others. - Tony Lauck 19:06:03 07/16/09 ( 2)
- RE: No, there are others. - Spendor Harbeth 20:00:23 07/16/09 ( 1)
- to put it bluntly - Werner 01:31:35 07/17/09 ( 0)
RE: What is wrong with digital-TAS Meridian CD & Speaker reviews - chris.redmond2@bushinternet.com 08:49:42 07/5/09 ( 20)
- to Messrs. Redmond and Hansen - Werner 00:31:11 07/6/09 ( 19)
- RE: to Messrs. Redmond and Hansen - Charles Hansen 23:17:52 07/6/09 ( 4)
- RE: to Messrs. Redmond and Hansen - Werner 23:36:07 07/6/09 ( 3)
- RE: to Messrs. Redmond and Hansen - Charles Hansen 18:10:33 07/7/09 ( 2)
- RE: to Messrs. Redmond and Hansen - Werner 23:40:32 07/7/09 ( 1)
- RE: to Messrs. Redmond and Hansen - Charles Hansen 22:54:16 07/8/09 ( 0)
- Theory vs. Real World........ - Todd Krieger 08:52:36 07/6/09 ( 13)
- and to end Wadia-style - Werner 11:07:13 07/7/09 ( 0)
- all linear phase now ... - Werner 10:45:00 07/7/09 ( 0)
RE: Theory vs. Real World........ - Werner 07/6/09 10:42:55 07/6/09 ( 10)
- You have hit the nail on the head - Charles Hansen 23:25:20 07/6/09 ( 0)
Nice Trick........ - Todd Krieger 21:43:57 07/6/09 ( 7)
- RE: Nice Trick........ - Werner 22:29:31 07/6/09 ( 6)
- RE: Nice Trick........ - Todd Krieger 22:54:30 07/6/09 ( 5)
- now that's a nice trick - Werner 23:42:36 07/6/09 ( 4)
- RE: now that's a nice trick - Todd Krieger 00:12:30 07/7/09 ( 3)
- RE: now that's a nice trick - Werner 00:32:03 07/7/09 ( 2)
- That's Not the Point........ - Todd Krieger 01:12:06 07/7/09 ( 1)
- RE: That's Not the Point........ - Tony Lauck 07:59:18 07/7/09 ( 0)
Thank you for saving my evening. - Tony Lauck 14:59:46 07/6/09 ( 0)
RE: What is wrong with digital-TAS Meridian CD & Speaker reviews - Adriel 17:08:03 07/4/09 ( 5)
- I more or less agree with you... - bjh 08:21:32 07/6/09 ( 0)
RE: What is wrong with digital-TAS Meridian CD & Speaker reviews - hikejohn 07:57:54 07/5/09 ( 3)
- The problem is... - mkuller 11:41:57 07/5/09 ( 2)
- RE: The problem is... - bjh 08:29:21 07/6/09 ( 1)
- RE: The problem is... - Peter H-son 09:25:16 07/10/09 ( 0)