Easy TTL to S/PDIF coax converter - 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 27th January 2009, 12:54 PM   #1
diyAudio Member
 
Join Date: Jul 2005
Location: Manchester
Default Easy TTL to S/PDIF coax converter

I want to connect a cdrom drive to a DAC using the dacs coaxial input but assume I need a converter (TTL --> coax).

I've seen a few examples some using the 74HC04 and some just using a couple of resistors and a capacitor.

Can anyone recommend a circuit that they have tried and works. Any diagrams / pictures will be greatly appreciated.


Has anyone using the circuit below succesfully with a cdrom?


100nF
TTL ----||-----330ohm--+--------- coax S/PDIF signal out
in |
100ohm
|
Ground -----------------+--------- coax signal ground




Cheers
  Reply With Quote
Old 27th January 2009, 06:29 PM   #2
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
I know the circuit around a 74HCT04 well, I built it more than once.

I recently built a S/PDIF-switch which I loosely based on these schematics. In it you'll also find the TTL to coaxial S/PDIF output. Based on a design I saw a long time ago I changed the 150nF C to 3x 47nF in parallel. Works fine, very near the S/PDIF specs of 75 ohms output impedance and 0.5 Vpp signal (when terminated with 75 ohms or an input).
Attached Images
File Type: gif image7.gif (6.0 KB, 1088 views)
  Reply With Quote
Old 28th January 2009, 05:00 AM   #3
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
Come to think of it, for my Shigaclone project, I just used the 374R and 93R1 to GND to divide the TTL-signal coming straight from the digital output of the signal processing IC, no 74HCT04. Most other people did the same, so the output seems to be able to cope with the current.
If your source will be able to supply enough current then you could do the same, otherwise you'd need the 74HCT04.
  Reply With Quote
Old 8th December 2010, 02:06 AM   #4
diyAudio Member
 
Join Date: Oct 2010
ramdog12345,

Your diagram misses a 100-ohm resistor, which should connect across the two "+" sign on your diagram.

I had built it before. It works fine.
  Reply With Quote
Old 9th December 2010, 01:35 AM   #5
macboy is offline macboy  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Ottawa, Canada
I've never understood why people try to use digital logic gates to drive S/PDIF cables. A proper analog line driver is what you should want. Don't forget that a digital signal is fundamentally just special kind of analog signal. An opamp (appropriate to the task) would work nicely, or even a video line driver. Coax S/PDIF has the same basic specs as composite video (75 ohm impedance, 0.7 VRMS, >6 MHz BW, etc.) so using a video line driver makes sense.
  Reply With Quote
Old 18th February 2012, 02:33 PM   #6
diyAudio Member
 
Join Date: Nov 2011
Location: Athens, Greece
I i connect th spdif out of a cdrom to a coax in of an AV reicever and don't work. I have a multi input selector (usb, toshlink, coax) that can lock with this simple circuit but reicever don't. I think that need biger resistor. Any opinion?
  Reply With Quote
Old 20th February 2012, 01:49 PM   #7
diyAudio Member
 
Join Date: Nov 2003
Location: Near PARIS
hello
Try to connect directly the digital output signal from the CD to the DAC Spdif input .....
I do it and it's work with a CS8416 .....
It's not the best solution but if you have no oscillo !!!!!!!it's not easy to debug

Best regards
Serge
  Reply With Quote
Old 3rd March 2012, 06:53 AM   #8
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
Agreed, the output of the CDROM drive probably already conforms to SPDIF standards (i.e. no TTL-levels but SPDIF-levels) and connecting it directly to the DAC/AV-receiver should work.
  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
Optical 2 S/pdif converter? Ryssen Digital Line Level 21 29th January 2009 11:05 PM
difference in s/pdif digital coax out? Scott_fx Digital Source 2 23rd October 2006 07:38 PM
S/PDIF to analog converter Limhes Digital Source 4 29th April 2005 01:55 AM
S/Pdif coax out besides opto Thoru Digital Source 0 3rd March 2005 03:20 PM
a/d converter 24bit 96khz s/pdif recording JBL Digital Source 1 10th January 2003 11:58 PM


New To Site? Need Help?

All times are GMT. The time now is 02:06 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