[Scott Dorsey]

Ludwig77 wrote:
I played a gig using my laptop to play backtrack MP3s.

The MP3s were recorded in stereo. I was running out my laptop's
headphone out jack via a cable that converts 1/8" to 1/4'. I ran that
to a direct box and then to the board.

It seemed that some instruments were missing. Would I be right to
theorize that I would have been losing one of the two speaker's in the
stereo field via this routing?

Yes. One channel is tip, and goes to your output. The other channel is
ring, and goes to ground.

If so, how would I be able to ensure that both stereo tracks would
have been routed to the mono signal?

You can make an adaptor with a TRS plug, with T and R both wired through
1K resistors to the T of your 1/4" TS plug. I make a similar adaptor with
47 ohm resistors for my wife to listen to headphones, since she has only
one working ear.

Or, you can set it all to mono in software, which seems like the easiest
solution.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."