Fibre optic - AT&T style (HP, Optek,...) - 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 13th March 2009, 11:29 AM   #1
TJF is offline TJF  Germany
diyAudio Member
 
Join Date: Jan 2009
Location: Munich
Default Fibre optic - AT&T style (HP, Optek,...)

I will bring a thread from the Pass Labs forum to this place, where it belongs to (now ).

Perhaps someone has an idea to bring this to an effective solution (used transmitter/receiver and not too extreme schematic). There do exist solutions with only 2-3 electronic parts...

Summing-up: Years ago there were these AT&T parts with ST-connectors (CTS 1361AAC) in some digital units like Wadia, ...
Actually there are i.e. these faster things (Optek, HP-Avago,...) on the market:

- HP with a rather wasteful schematic at figure 21 (for 1414 and 2418 - also from Optek)

- Optek OPF694-2 and OPF562

Optek recommends this more friendly schematic

Does anyone have an idea, how to go on ...
  Reply With Quote
Old 14th March 2009, 04:50 AM   #2
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
The Fig.21 schematic is a combined tx and rx with ECL logic, while the optek datasheet shows a TTL tx driver only. The HP App Bulletin has the same TTL TX driver shown as figure 8.

I've found a slightly more appropriate RX circuit in another HP datasheet designed for lower speed operation but should still be more than adequate for audio. It uses a 2416 RX module and a single LT1016 comparator. Ignore the HFBR-25x6 as that can be left out.

See Figure 4.
www.avagotech.com/docs/AV02-0723EN
  Reply With Quote
Old 14th March 2009, 12:50 PM   #3
TJF is offline TJF  Germany
diyAudio Member
 
Join Date: Jan 2009
Location: Munich
Yes Looks good - even with Gerber files...

By the way: I saw that Optek OPF 694 and 562 would be a wrong combination!
  Reply With Quote
Old 15th March 2009, 08:27 AM   #4
Zoran is offline Zoran  Serbia
diyAudio Member
 
Join Date: Jan 2004
Location: Belgrade
this is from the
EMM lab CDSD model player
aglient HFBR-1414T tx and HFBR-2416T rx
.
good link
http://www.avagotech.com/pages/en/o...ring/hfbr-1414/
Attached Images
File Type: jpg emm-lab-cdsd-fiberoptic.jpg (82.2 KB, 453 views)
__________________
###
  Reply With Quote
Old 15th March 2009, 11:16 AM   #5
TJF is offline TJF  Germany
diyAudio Member
 
Join Date: Jan 2009
Location: Munich
Yes Zoran. Thank you! That are exactly the things (Emitter and Receiver) we want to use. But please read in spzzzzkts -link (post #2) about "Arbitrary Duty Factor" and have a look at Figure 4. May be EMM is using any kind of "normal" circuit ... ?

Your link doesn't work. I think it should be this
  Reply With Quote
Old 15th March 2009, 11:41 AM   #6
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Hi Zoran,

I agree that 1414/2416 pair is the way to go and have ordered one of each to try out. The older ODL 50 series II used in the wadia, pass d1, etc would be ideal - it's easy to implement but is extremely hard to get a hold of as appears to have gone out of production by around 2000. A couple of brokers list it as stocked but they don't bother replying to enquires on "diyaudio" quantities.

The driver circuit for the 1414 given in the HBRF-0400 series datasheet is fine for our purposes. Unfortunately there is no real detail given on RX circuits.

Application Bulletin 78 (linked in TJF's first post) initally looked promising but the rx circuits contained in it are designed for 155MBd operation over long distances, and utilise ECL logic with conversion to TTL levels.

Application Note 1121 (link in my post above) seems more appropriate to audio transmission speeds and the rx circuits are designed for lower speeds - up to 32MBd - and operate at TTL levels.

An observation on the drivers for the TX - the recommend circuit uses a 74ATCQ00. It's important to make the distinction as ACT logic is widely regarded as inappropriate for audio use due to it being quite noisy - a search on the archives will turn up plenty of warnings not to use ACT chips. The ACTQ series is based on FACT Quiet logic and is apparently a significant improvement over the older ACT logic design.

cheers
Paul
  Reply With Quote
Old 15th March 2009, 11:49 AM   #7
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Looks like EMM are using the app note circuits...

I can see a LT1016 near the RX. Nice to have some confirmation that we are on the right track.

Any chance of a clearer pic of the ACT series chips near the TX?
  Reply With Quote
Old 15th March 2009, 12:09 PM   #8
TJF is offline TJF  Germany
diyAudio Member
 
Join Date: Jan 2009
Location: Munich
... near TX I see no 74ACTQ00 ...

Thomas
  Reply With Quote
Old 15th March 2009, 12:26 PM   #9
TJF is offline TJF  Germany
diyAudio Member
 
Join Date: Jan 2009
Location: Munich
Hi Paul,

Quote:
The older ODL 50 series II used in the wadia, pass d1, etc would be ideal
I don't think so meanwhile ... This 32 MBd way seems to be very promising.

By the way: Stereo 192 kHz/24 doesn't come over 10MBit/s ...

Regards
Thomas
  Reply With Quote
Old 15th March 2009, 12:27 PM   #10
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
What are you going to use it for?
Remember that you may need some channel encoding for zero DC and enough signal transitions for clock recovery to work.
I suggest you use some of cheap SFP transceivers, they are easiest to use or if you find some "1x9" transceivers.

Ps. These optek transceivers look great, this would be FAR better than any plastic fiber connection.
My note on zero DC applies only to laser transmitters, also I think if you stick to SPDIF you don't need to worry about transitions frequency, because SPDIF clock/data recovery already knows how to recover it.
  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
Fibre optic DAC? bacon665 Parts 1 29th June 2009 01:09 AM
USB to Optic (Toslink) nitropowered Solid State 2 2nd July 2002 12:57 AM


New To Site? Need Help?

All times are GMT. The time now is 07:57 PM.


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