[Richard Crowley]

"Asorka" wrote ...
Simple question.
Typical line-out/phones output on digital devices (mp3 players/
computers) is stereo, istruments amplifier (eg: guitars, basses) is
mono.

If I make the link one chanell is lost. How should I do avoiding the
use of a proper mixer?
I'd like the right/left chanells to fuse together to one/mono chanell:
is that possible

I guess:
- if it's a computer I should obtain by the software interface... but
I'm using a Mac and VLC and don't know how (it will probably let me
choose just one channel)
- if it's not a computer (something with a basic UI) I should find a
cable which fisically fuse the two chanells together

Well, I hope to find some help and that you'll forgive my english :P

The simple and inexpensive method is to just use a "Y-cable"
which connects the Left and Right outputs together to form a
monaural signal combined from both. This is effective most of
the time, and with reasonable quality.

The prefered method is to use "build-out" or "mixing" resistors
in series with each of the outputs (Left and Right). This prevents
the Left output from affecting the Right output and vice-versa.

But this scheme is not generally available pre-assembled.
Because it somewhat depends on the output impedance
of the source and the input impedance of the destination,
the value of the resistors must be selected for optimal
performance.

For casual use, using a simply "Y-adapter" is likely OK.