Asserting Emphasis flag in S/PDIF stream - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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 13th January 2007, 02:10 AM   #1
diyAudio Member
 
Join Date: Jan 2007
Default Asserting Emphasis flag in S/PDIF stream

Hello, there! Just joined.
Are there any chips obtainable by an amateur that can assert the Emphasis flag in S/PDIF stream?

Behringer's SRC2496 has this feature but I have to control this asserting from Mac. I may electrically "push" the SRC2496's EMPH switch from Mac. But this switch seems to be a toggle switch (I only have the manual) and Mac will not know the current status of the switch.(I may tap the LED indicator for Mac by USB but it's too complicated for me.)

My main audio source is a satellite PCM radio that transmits pre-emphasized digital audio signal with 15us/50us protocol. S/PDIF output of the PCM radio tuner is emphasized and I record it in my Mac with Apple-Lossless format. When I play recorded audio files in iTunes through USB audio interface, I have to de-emphasize them. Currently I use custom equalizer for iTunes and a simple analog RC-filter for iPod in my car. A freeware "sox" can de-emphasize audio files but it needs conversion of file format and it takes too much CPU resources. I also record analog FM radio and CD in Mac and these music files do not need de-emphasis, of course.

I'm not too satisfied with iTunes custom equalizer and planning to de-emphasize by hardware. Currently, I use Pioneer DAT's DAC connected to Burr Brown USB audio chip by S/PDIF. I may use the same simple analog RC-filter for iPod but I plan to replace my analog amplifier by full-digital amp so I need digital de-emphasis. I did simulation of the RC-filter by Spice and the result indicates phase shift in some frequency range, which is also a reason I hesitate to use a simple RC-filter.

I'm not so confident in digital audio circuit design and assembling, so the best way to de-emphasize digitally is, I think, to assert Emphasis flag in S/PDIF sound stream so that DAC or digital amp de-emphasizes the audio stream. It may be accomplished by CPLD or by very fast one-chip microcomputer, but it seems to be much easier if I can obtain a dedicated audio chip.

iTunes is so useful and I'm transferring my audio sources such as CDs, DATs, cassette tapes into HDD. So I need to control de-emphasizing from Mac.

Thanks for reading.
  Reply With Quote
Old 13th January 2007, 04:12 PM   #2
diyAudio Member
 
Join Date: Oct 2001
Location: .
The '2496 has two emphasis LED's, one for the input section and one for the output section. If emphasis is asserted, the input section LED will light up but as SPDIF flags are considered unreliable the '2496 can assert or de-assert emphasis as needed in the output stage. I do not think the '2496 performs de-emphasis, merely display its presence or absence.


  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
S/PDIF Optical to S/PDIF RCA Replacement PrecisionAudio Digital Source 2 11th February 2007 09:35 PM
Defeating DVD-A copy prevention flag pooge Digital Source 4 1st April 2005 02:24 PM
Can't acess the flag JBL Forum Problems 5 6th February 2003 02:07 AM
Upsampling DAC and De-Emphasis flag? pquadrat Digital Source 3 6th December 2002 02:01 PM
Must See! -> the Flag thread turns into more booze darren Everything Else 85 12th November 2002 09:46 PM


New To Site? Need Help?

All times are GMT. The time now is 01:37 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