There might be a whole other problem that goes along with preamps that invert phase: Does it mean that your cable to the amp is sending the negative signal through the positive conductor and visa-versa?!! Think about it... most cables are designed to handle both these polarities in very different ways and if the preamp inverts them, you have just tossed out all the cable's design .I have only seen one cable that is offered specially configured for inverted phase signals, and that was the Mapleshade.
