Hi Vasco,
PWH is suggesting that you can wire the left and right channels either in
parallel or in
series.
Do you remember any physics from school days?
Think of each channel of the cartridge as a battery if it helps. You can wire two batteries in parallel (+ to + and - to -) or in series (as in a 2-battery torch, with the + of one battery is connected to the - of the other, with the bulb connected to either end of the chain).
Here's a pic from the web (albeit with 4 batteries rather than 2); the top shows parallel connection, the lower series.
http://ctaps.yu.edu.jo/physics/Cours...s_parallel.gif
I hope that helps
Nick.
P.S. I do know that a "battery" is not the same as a "cell" but I'm trying to keep things simple here