Are you sure that the Apex tv audio input is not a combined Left/Right Input Jack?

I have in the past found that just sliding the male jack in partaily can change the output audio signal you are listening to.

Check the tv and make sure it is Mono and not stereo using a combined input jack. Usually a mono tv had just one speaker.

Apex electronics I believe can have undocumented features as they may use other manufactures chip sets which may or may not have documented features.

Don't hold me to this as I don't own a Apex unit. Just a wag here.

Cybervision and Entvideo is like that also. Consequently hitting a button could take you somewheres that the owners manual has no explanation for.

-Don B