"direct connection" for spdif

[Graz]

apologies in advance for my noobness.

i presently use an external usb sound card (m-audio transit) with my laptop. the output of this soundcard runs to an external dac (ciaudio vda-1).

i want to bust open the usb sound card & add it directly into my dac.

my entire question is really all about directly connecting the spdif output of the sound card to the dac. i'm talking about a connection length of no more than a few inches.

i've read a lot about jitter and termination & lots of statements about how long spdif cables are better. what about very short connections? is this bad?

also, what about termination? what's the best way to ensure proper 75 ohm termination? should there be 75 ohm impedance between signal & ground at the source or at the destination? what about galvanic isolation...is this a must?

as you can see, i don't understand squat about spdif. but, i'm determined to perform this mod...i just wanna do it right.

thanks in advance for any advice.

peace,

graz

[tubesguy]

I think that you really want to do away with SPDIF entirely. I believe that one of the commercial modders (Empirical) installs the Transit inside the target DAC or home theater receiver, using, if I understand it correctly, an I2S connection from the Transit chip to the target's digital receiver chip.

More knowledgable folks may join in and correct me - Pat

[MWP]

It depends on how the sound card works.
If there is a big IC that just pumps out SPDIF (no I2S), then thats what youll have to use.
Use it at TTL level though, dont use the coax/optical reciever/transmitter level changers, amps, etc.

If there is a separate SPDIF transmitter IC (turns I2S into SPDIF), itll be best to use the I2S signal.