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-   -   Source for 3.5 mm (1/8 in) optical S/PDIF transmitter (http://www.diyaudio.com/forums/parts/165914-source-3-5-mm-1-8-optical-s-pdif-transmitter.html)

wachuku 28th April 2010 06:24 AM

Source for 3.5 mm (1/8 in) optical S/PDIF transmitter
 
Mods (if you see): I posted this earlier today in a less appropriate section (Digital line out); could you delete my post from that section since nobody replied at time of submission of this post?

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Recently I used a laptop PC (not mine) where the 3.5 mm audio headphone jack doubled as an optical S/PDIF audio transmitter. I have also seen the dual purpose headphone-S/PDIF 3.5 mm jacks on other PCs. Does anyone know if these types of jacks can be purchased somewhere?

For example the parts supplier digikey lists Toshiba part number TOTX147L(F,T) which is a 3.3V 96kHz optical S/PDIF transmitter with the "standard" optical S/PDIF cable connecter. I cannot however find optical S/PDIF transmitters in a 3.5 mm TRS jack configuration. (Nor can I find what I'm really looking for: a 3.5 mm jack serving as a "dual" output with the possibility of either an electrical headphone output or an S/PDIF optical output).

Anyone aware of any sources?

theAnonymous1 28th April 2010 04:46 PM

I tried looking for the same thing about 2 years ago with no luck and eventually gave up my search. :(

If you ever find one, please do tell.

wachuku 28th April 2010 06:50 PM

That's strange. I wonder where do the PC manufacture's get them?

macboy 28th April 2010 07:06 PM

Digi-key: search for "tx audio mini"
Results are non-stock but some have minimum order qty of 1.

wachuku 29th April 2010 02:20 AM

macboy -- NICE!!! That's exactly what I was looking for. Thanks.

Now I'm also looking for similar receivers (1/8 in dual electrical/optical) -- any ideas with those?

star882 29th April 2010 02:52 PM

Use a 3.5mm connector with an open back and add a laser diode behind it. No lens is needed since the tip of the cable is the lens. I once used the laser diode from a cheap laser pointer to add optical output to my Sound Blaster Live! 24-bit. To get optimum alignment, plug a fiber cable into the connector, point the other end at a wall, power the diode and move it until the spot is the brightest. Then glue the diode in place.

For a receiver, use a photodiode instead of a laser diode.

macboy 30th April 2010 01:48 PM

You don't need even a laser diode, just an LED. The big standard T5 won't work well, but if you use a nice bright SMD one right up against the cable like you said, it will work.

For the Rx, I'd use a module for that. It's not as simple as "use a photodiode" - you need to bias the thing, filter the output, apply automatic gain control, etc. Not easy (doable but not easy). But one could dissect a standard TOSLINK receiver and place the guts behind the 3.5 mm jack. Since the light just kind of spews from the cable end (quite in contrast to "real" fiber optics where the cable is a fraction of a mm wide) you just need to get it close, and block out external light.

wachuku 30th April 2010 05:38 PM

Quote:

Originally Posted by macboy (Post 2171054)
...But one could dissect a standard TOSLINK receiver and place the guts behind the 3.5 mm jack. Since the light just kind of spews from the cable end (quite in contrast to "real" fiber optics where the cable is a fraction of a mm wide) you just need to get it close, and block out external light.

I was wondering about that for the Rx. Would there be any problems with different paths to the receiver and light "bouncing around" to cause bit errors?

And apparently nobody is yet aware of a 1/8 in dual electrical-analog / optical-S/PDIF receiver?

wachuku 30th April 2010 05:39 PM

Also is star882 a robot or a person?

star882 30th April 2010 10:31 PM

Quote:

Originally Posted by wachuku (Post 2171306)
I was wondering about that for the Rx. Would there be any problems with different paths to the receiver and light "bouncing around" to cause bit errors?

And apparently nobody is yet aware of a 1/8 in dual electrical-analog / optical-S/PDIF receiver?

If you have some way of accessing the photodiode signal before the comparator, you can use an oscilloscope to check the signal level. Or loosen the connector and if it doesn't drop out until it is very loose, it's good.


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