IPB

Welcome Guest ( Log In | Register )

A secret "known by signal processing experts" or nonsense?
adamdea
post Jan 10 2013, 17:16
Post #1





Group: Members
Posts: 24
Joined: 31-August 11
Member No.: 93396




http://www.wickeddigital.com.au/index.php/...eally-necessary
Sets out what is described as a White Paper by Marco Manunta of M2Tech. It contains the following passage (my emphasis)

"But there is something more. Itís known by signal processing experts, and absolutely not popularized amongst music lovers, that converting an analog signal into a discrete-time one (as it happens when converting from analog to digital) destroys the phase information in the two top octaves of the resulting spectrum. In a CD-standard digital recording, all phase information are lost from 5.5kHz up to 22kHz,"

Can any signal processing experts comment on whether this is true or not, and if so why. As a mere layman I am not able to understand why it even might seem be true.
Go to the top of the page
+Quote Post
 
Start new topic
Replies
adamdea
post Jan 10 2013, 23:08
Post #2





Group: Members
Posts: 24
Joined: 31-August 11
Member No.: 93396



Thanks everyone, I thought it seemed like nonsense but I wanted to check unless it referred to some little known effect. I can understand that analog brickwall filters could mess with phase, but am relieved that there does not appear to be an insurmountable problem.

I may take this up with m2tech.
Go to the top of the page
+Quote Post
Arnold B. Kruege...
post Jan 11 2013, 16:58
Post #3





Group: Members
Posts: 4286
Joined: 29-October 08
From: USA, 48236
Member No.: 61311



QUOTE (adamdea @ Jan 10 2013, 17:08) *
Thanks everyone, I thought it seemed like nonsense but I wanted to check unless it referred to some little known effect. I can understand that analog brickwall filters could mess with phase, but am relieved that there does not appear to be an insurmountable problem.

I may take this up with m2tech.


Above some frequency in what we call midrange, the ears lose their ability to discern phase. This is because our ears are built like spectrum analyzers, but only what we call the real portion or amplitude is conveyed to the brain. If you wish to obtain phase information from a spectrum analyzer you need two independent kinds of (quadrature) data for each frequency band. Our ears only pass one kind of information to the brain for each frequency band above medium frequencies.

One consequence of this loss of phase information in our ear/brain interface is that massive amounts of phase shift (e.g. 1,000 degrees or more) can be applied to critical high resolution audio signals, with no discernible change in perception. The only caveat is that the phase shift applied to both channels must be essentially the same or else the phase shift will turn into response changes that will be audible. Above 5 Khz this situation dominates with total supremacy.

So even the old CD players with analog filters did have fairly well matched channels, and while what they did to phase was not numerically pretty, there wasn't any serious effect.

Another ugly thing that old CD players sometimes did is share the same DAC between the 2 channels so that their outputs were 1/2 sample time apart. If you electrically summed the two channels this led to a minor frequency response roll-off that on a really good day might be mildly audible.

Go to the top of the page
+Quote Post
dhromed
post Jan 11 2013, 17:12
Post #4





Group: Members
Posts: 1337
Joined: 16-February 08
From: NL
Member No.: 51347



QUOTE (Arnold B. Krueger @ Jan 11 2013, 16:58) *
massive amounts of phase shift (e.g. 1,000 degrees or more)


Erm, wouldn't that just be a 1000 mod 360 = 280 degrees phase shift?

Or maybe I should get me one of those pointed caps.
Go to the top of the page
+Quote Post

Posts in this topic
- adamdea   A secret "known by signal processing experts" or nonsense?   Jan 10 2013, 17:16
- - greynol   It's complete nonsense. But hey, it's the ...   Jan 10 2013, 17:31
- - saratoga   QUOTE (adamdea @ Jan 10 2013, 11:16) Can ...   Jan 10 2013, 17:33
- - DonP   QUOTE (adamdea @ Jan 10 2013, 11:16) http...   Jan 10 2013, 17:44
- - jmvalin   QUOTE (adamdea @ Jan 10 2013, 11:16) ...   Jan 10 2013, 18:19
- - Kohlrabi   Their website is filled with various other nonsens...   Jan 10 2013, 18:33
- - eahm   Thank you adamdea, now we all need a 5.6MHz/1mbit ...   Jan 10 2013, 19:01
- - mzil   QUOTE (adamdea @ Jan 10 2013, 12:16) http...   Jan 10 2013, 19:54
|- - db1989   QUOTE (mzil @ Jan 10 2013, 18:54) However...   Jan 10 2013, 21:09
- - adamdea   Thanks everyone, I thought it seemed like nonsense...   Jan 10 2013, 23:08
|- - Arnold B. Krueger   QUOTE (adamdea @ Jan 10 2013, 17:08) Than...   Jan 11 2013, 16:58
|- - dhromed   QUOTE (Arnold B. Krueger @ Jan 11 2013, 16...   Jan 11 2013, 17:12
||- - saratoga   QUOTE (dhromed @ Jan 11 2013, 11:12) QUOT...   Jan 11 2013, 17:22
|- - mzil   QUOTE (Arnold B. Krueger @ Jan 11 2013, 11...   Jan 11 2013, 17:58
||- - Arnold B. Krueger   QUOTE (mzil @ Jan 11 2013, 11:58) QUOTE (...   Jan 11 2013, 21:31
||- - mzil   QUOTE (Arnold B. Krueger @ Jan 11 2013, 16...   Jan 11 2013, 23:33
||- - Kees de Visser   You're being mean with old men (like me)   Jan 12 2013, 10:25
|- - Ethan Winer   QUOTE (Arnold B. Krueger @ Jan 11 2013, 10...   Jan 11 2013, 21:27
||- - jmvalin   QUOTE (Ethan Winer @ Jan 11 2013, 15:27) ...   Jan 11 2013, 22:26
||- - Ethan Winer   QUOTE (jmvalin @ Jan 11 2013, 16:26) Actu...   Jan 12 2013, 19:32
||- - Woodinville   QUOTE (Ethan Winer @ Jan 12 2013, 10:32) ...   Jan 12 2013, 20:21
|||- - Ethan Winer   QUOTE (Woodinville @ Jan 12 2013, 14:21) ...   Jan 13 2013, 20:03
|||- - jmvalin   QUOTE (Ethan Winer @ Jan 13 2013, 14:03) ...   Jan 13 2013, 20:17
||- - jmvalin   QUOTE (Ethan Winer @ Jan 12 2013, 13:32) ...   Jan 13 2013, 08:46
|- - Woodinville   QUOTE (Arnold B. Krueger @ Jan 11 2013, 07...   Jan 12 2013, 20:17
- - Arnold B. Krueger   QUOTE (adamdea @ Jan 10 2013, 11:16) http...   Jan 11 2013, 03:58
- - greynol   Detection of phase differences between channels do...   Jan 11 2013, 20:32
|- - mzil   QUOTE (greynol @ Jan 11 2013, 15:32) Dete...   Jan 11 2013, 21:31
- - greynol   @Ethan: I hope this isn't, "I tried it on...   Jan 11 2013, 21:32
|- - Ethan Winer   QUOTE (greynol @ Jan 11 2013, 15:32) I ho...   Jan 11 2013, 22:00
- - greynol   I did not take the OP as meaning phase relation be...   Jan 11 2013, 21:39
- - Woodinville   QUOTE (adamdea @ Jan 10 2013, 08:16) http...   Jan 12 2013, 20:14
- - greynol   Delay by a half sample: up-convert to a higher sam...   Jan 13 2013, 20:09
- - Woodinville   QUOTE (greynol @ Jan 13 2013, 11:09) Dela...   Jan 14 2013, 03:16
- - Ethan Winer   Oh, you math guys... Though I do understand up-sa...   Jan 15 2013, 21:42


Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 26th November 2014 - 10:27