Wolfson's Elastic Buffer SPDIF receiver ? - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 3rd February 2009, 11:03 PM   #1
percy is offline percy  United States
diyAudio Member
 
Join Date: Apr 2004
Location: MN
Default Wolfson's Elastic Buffer SPDIF receiver ?

Found this AES paper from Wolfson's website - http://www.wolfsonmicro.com/uploads/...Oct%202006.pdf

But I couldn't find any of their spdif receiver products that have this architecture ? Did wolfson ever start production of this kind of receiver ?

Does anyone else make an spdif receiver that works on the same principal ?
  Reply With Quote
Old 4th February 2009, 01:37 AM   #2
diyAudio Moderator Emeritus
 
Iain McNeill's Avatar
 
Join Date: Oct 2007
Location: Santa Cruz, California
Call me a naysayer but I think all these schemes are flawed. This one appears to have a small buffer and then they continually speed up or slow down the data out clock to stop the buffer over/under-flowing. Not particularly original.

By keeping the output clock fixed for short periods of time and occasionally making incremental changes, the instantaneous jitter is reduced by an order of magnitude - Bravo! But there are still going to be small temporal distortions over the time frame of a song/album/movie.

I'm still not convinced that the ASRC method which is currently in vogue is any better. Here, the incoming data, which we assume has been recorded with a jitter free clock is arriving at a non-constant data rate. The idea of upsampling to a massively oversampled clock and then phase interpolating the samples to the output clock points in time is equally disruptive.

Ideally, you'd just output those precisely recorded samples at a constant rate.

I still think the best way is to have a HUGE buffer, I'm talking like a GB or so and just play everything back at 0.1% slow to a rock solid clock. OK by the end of the movie you'd have accumulated a couple hundred meg of buffered data, the movie would go on for a few minutes after the DVD stopped spinning. No biggie, small price for perfect playback.
  Reply With Quote
Old 4th February 2009, 03:39 AM   #3
Wodgy is offline Wodgy  United States
diyAudio Member
 
Join Date: Jul 2003
Send a message via AIM to Wodgy
For what it's worth, the eye diagrams in the AES paper you link to are reproduced in this white paper analyzing the performance of the WM8804/5:
http://www.wolfsonmicro.com/uploads/...May%202007.pdf
So it's probable that the WM8804/5 do include "elastic buffers" even though this isn't specifically mentioned in their datasheet.
  Reply With Quote
Old 4th February 2009, 02:53 PM   #4
percy is offline percy  United States
diyAudio Member
 
Join Date: Apr 2004
Location: MN
Wodgy, yes I saw that paper too, but I was hoping to find a more definite confirmation. Even the functional block diagram of the chips in both their datasheets as well as this paper don't reveal anything specific in that matter.
  Reply With Quote
Old 4th February 2009, 04:14 PM   #5
percy is offline percy  United States
diyAudio Member
 
Join Date: Apr 2004
Location: MN
The only other unofficial reference I found to this is - http://www.electronicsweekly.com/Art...chitecture.htm

It does say that "The firmís WM8804 and WM8805 chips include the new scheme"
  Reply With Quote
Old 7th February 2009, 04:22 PM   #6
percy is offline percy  United States
diyAudio Member
 
Join Date: Apr 2004
Location: MN
this becomes interesting - contacted Wolfson directly, I was told their current spdif receivers (wm8804/5) do NOT have the elastic buffer technology. I wonder how in the world then are they able to acheive that feat ?? As shown in a chart (pg 5, fig 2) jitter rejection in the wm8805 starts as early as 100hz and increases dramatically by 1-2Khz.
  Reply With Quote
Old 8th February 2009, 02:46 AM   #7
diyAudio Member
 
Join Date: Aug 2008
haha , good to know, thanks percy , maybe they should discontinue their dac and put that receiver into production
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Multiformat SPDIF receiver quantran Digital Source 3 2nd April 2007 11:29 AM
WTB: CS8413 spdif receiver Alexandre Swap Meet 3 19th August 2006 11:11 PM
DAC design | First step: SPDIF receiver webzeb Digital Source 9 6th February 2006 10:11 PM
SPDIF receiver Darth freudius Digital Source 1 25th August 2005 01:33 PM
SPDIF Input Receiver & MUX JHertz Digital Source 4 29th May 2003 03:22 PM


New To Site? Need Help?

All times are GMT. The time now is 05:17 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2