[star882]

I got the PCM2902 USB audio chip working (the USB interface at least), but I have some questions.
For the S/PDIF input (coax), should the receive amp invert the signal or not? Would it be possibe to use one connector for both digital and analog input, with the chip autoselecting the type? (I'm putting the circuit into the case from an old USB drive so it must be small.)
If I include an optical out, the laser diode must switch on when the output line is high, right? (Also, would a laser diode without a lens work? Again, it must be small so it will fit. It will be mounted behind the analog output connector so an adapter will be all that's needed to get digital optical out.)
For the laser, would an IR diode from an old CD-ROM drive work? I have plenty of IR diodes and they normally have the case grounded. (The red ones usually have the case connected to the power supply so if the tip of the plug touches it, it would short out the supply!)

BTW, it's for a laptop.

 

[Nisbeth]

1) The S/PDIF-signal is non-polarised, so inverting/noninverting doe not matter.

2) For optical input/output use a TORX/TOTX receiver/transmitter. If you want a combination unit with an analog plug I belive you can get these as well, they are just (much) harder to find.

If you want to play with building your own optical unit I belive the output is visible red light (somewhere between 635 and 670 nm), but you need special hi-speed LEDs to get a proper signal across

/U.

 

[rickcr42]

Quote:

If you want to play with building your own optical unit I belive the output is visible red light (somewhere between 635 and 670 nm), but you need special hi-speed LEDs to get a proper signal across

some of those DIY whack jobs at the mini disc site have done just that and even using visible light LEDs !!!

If there is a way someone somewhere will figure out how so it is just a matter of finding the "who"

here is the site

http://www.minidisc.org/whole_page.html


The DIY stuff is near the bottom 1/4 of the page but be warned a lot of the links are presently leading no where so may take some digging to find new ways to get to old pages (wayback machine

)

 

[rickcr42]

Whack job exibit A :

http://www.minidisc.org/cdrom_opticalout.htm

some of these guys are totally off the hook and i love it