On Wed, 21 Jul 2010 18:53:58 -0700, William Sommerwerck wrote:

- snippage-

Assuming that both channels have the same output impedance, and the output
levels are closely matched,

.. and, assuming both outputs are _exactly_ in phase,

then (if the outputs are directly paralleled)
there will be /no/ current flow from one channel into the other, ....

Jonesy