Summing two channels with transformers

As a strarting point I have two separate channels with output transformers on each. If I connect the secondary winding of these two transformers in series, I get the sum of the two channels. I've tried this with a passive DI-box I made and it seems to work as expected.

Combining the secondary windings in parallel would probably cause some extra effects, because one channel would be driving the other. In the series connection this unwanted situation does not happen. Is there anything wrong with this line of thought? Some phenomenon I should be concerned about?

I'm in the process of building the G9 and addung a switch that would connect the output transformers in series would essentially result into a two channels into one mixer. A nice extra feature that could be handy in some occations.

-martti-

have you looked at this?

http://www.jensentransformers.com/as/as094.pdf

I built one, it works, there is some insertion loss though. I havent yet used it on a session, but with some makeup gain, I expect it to be ok.

dave