In many cases bridging two channels of an amp requires nothing more than inverting the signal and applying at equal amplitude to the second channel, then taking the output between the two hot leads. There are limits, usually when bridging two amps rated at 4 ohms minimum you can't connect speakers lower than 8 ohms in bridged mode. Building a unity gain inverting preamp to connect between the inputs of the two channels would be the only problem. Maybe something for Outlaw to consider......