noise problem with digital line and s/i ss stage

[then_dude]

hello people,

i have an tda1545 non oversampling dac, it is a monica.
i supply 12v from an external lm317 (it has 2.2mv ripple).

anyway: i feed monica from the pc digital out, and a lot of distortion is coming along the coax line. when i plug the cable in an old dcc with digital in and headphone out, i don't hear any dirty pc noises. i even run the signal through the dcc and out of the machine straight into monica, and gone was the contamination.

so my first question is: can i put some components along the spdif coax cable so that the noises are eliminated ?

secondly i have also an i/v stage that i have build, but there is noise in it. i feed it with a 21v lm317 with also 2.2mv ripple. i use 5.6k and 220pf and a 4.7uf output cap. i replaced two out of 4 diodes with leds. (it is RB stage) i don't know how noisy it may be, but i'm listing at it with a headphone amp. (the headphone amp is rather quieted so i don't think that is the problem, well quite shure).

so can anybody help me out on this one.
thanx a lot
(ps the headphone amp is the ck2III)

greetings

[analog_sa]

Originally posted by then_dude

so my first question is: can i put some components along the spdif coax cable so that the noises are eliminated ?

Quite possibly it's ground noise from the PC. An spdif transformer at the input of your dac will sort this out. Diyaudio member Spencer has some very cheap Midcom spdif transformers you may want to try.

[then_dude]

thank you so much, i have emaild mr spencer.
do you have a sheme or something how to import this transformer into the dac ?

thanx a lot