I want to get unamplified sound between my computer & DAB radio (in
the kitchen) and my amplifier (in the sitting room). The cable route
is about 10-15m and goes through the cellar, so it would be nice to
have a socket there as well.

I have bought a couple of double phono sockets from nexxia
(http://www.nexxia.co.uk/) and linked them up with telephone wire
(which was what I had to hand). Not good. There's a hum, and
although reasonably loud music is worth listening to, speech is very
distorted.

Now I'm sure there are many things I have done wrong: using telephone
wire; maybe using solder (though the sockets have solder tags); I
should also mention that the cables connect through a telephone
junction box. But I can't find any cable anywhere specified for this
purpose (as opposed to speaker cable). What should I use (looking for
something cheap, that I can buy by the metre, or in a 10 or 25m reel,
either over the net or on the UK high street)? Also advice about a
junction box if that's likely to make a difference.

Many thanks in advance,

James