Well
that's the problem then! Most line outputs simply aren't intended
to drive the low impedance of headphones.
If you have something that can, then you are lucky, but you certainly
shouldn't expect it.
Agreed :)
-----
Little soldering and I have 2-mono-jacks ->
1-stereo-jack-plug cable.
Try adding series resistors in your jig above. Start with 1K ohm on each of the
channels.
Mess around adding different resistor values between the card and your headphones until it
sounds better.
A higher value of series resistor will make the phones sound better, but you will have to
boost the volume then. Optimum is earsplitting without clipping(you know the grind).
Tracey.