[eiouwa]

When using a soundcard as DAC and an external amplifier, which 3,5mm output (I've got 4 of them) of the soundcard does one have to use to connect the soundcard to the RCA inputs? The headphone / speaker out?

 

[Head Injury]

What soundcard do you have?

 

[eiouwa]

An X-Fi Extreme Audio, I believe. Either that or an Extreme Music

 

[obobskivich]

The "first" output - "Line Out 1"; refer to graphics:
 
Xtreme Music:
http://images10.newegg.com/NeweggImage/productimage/29-102-188-01.jpg
 
Xtreme Audio:
http://cdn1.techbargains.com/icache/2009/10/21/12561641242957.jpeg
 
Ensure the soundcard "knows" it's supposed to be outputting a stereo signal as well (Headphones or 2.0/2.1 Speakers).
 
 

 

[eiouwa]

Yes, that's the headphone output.

 

[obobskivich]

I feel as though I didn't answer your question...do you mean to ask how one would get RCA outputs from the soundcard, or were you simply meaning to confirm the use of that output?
 
If you need RCA outputs, there's a plethora of converter devices - just look for a 3.5mm TRS to RCA Stereo Adapter; pick whatever suits your fancy (cable, converter and cable, etc).
 
Quote:

Yes, that's the headphone output.

 

 

[eiouwa]

I just wanted to know the correct output for a 3,5mm to double RCA cable (soundcard 3,5mm out, amplifier RCA in), so you answered the question