Default Missing channel with every miniplug adapter

Regards!

I am having a very anoying problem with the miniplug sizes. Whenever I connect a male-male adapter (using the aux input of the car), or with an RCA adapter (for my 2.1 subwoffer), I loose a channel.
I suppose that it is because the adapters and plugs that I get (I am from Argentina) are a ****ing peace of ****.

does anyone have the same problem??

thanks!