The product in question is a power amplifier. When I asked how you reverse polarity with firmware you asked me in return if I have heard of relays.I never said you could. We certainly don't approach anything close to this.
Evidently the product in question is a preamp. I could see how this type of circuitry could be included.
Now I am asking again, how do you reverse polarity of a power amplifier with firmware without adding extra circuitry?