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Keith,
In order to bridge an amplifier the inputs must be driven out of phase. In other words, one channel must have the signal positive connected to the outer ring of an RCA plug, and the signal negative (i.e, the shield) connected to the center pin. This would normally require making custom connection cables; however, the bridging switch on an amplifier does this conversion internally.
You will notice, home theater receivers do not have such a switch. This is because they are not designed to be bridged. There is probably a very practical reason for this. After all, what good would a three-channel home theater receiver be??
If you’re adventuresome you could make the custom cables as outlined above. One channel must have the signal positive connected to the outer ring of an RCA plug, and the signal negative (i.e, the shield) connected to the center pin.
However, unless the receiver has amplifier input jacks (pretty rare on a receiver) it may not even work at all. Giving an out of polarity signal to an input on the receiver might shut the thing down. After all, you are accessing the pre-amp section here, not the amplifier’s inputs directly. Proceed at your own risk, because it is dangerous to bridge an amplifier that was not designed to be. Don’t be surprised if it goes up in smoke in short order.
Also keep in mind, the bridged channels will require speakers double the minimum factory impedance rating for single channels. Bridged amplifiers are not forgiving of improper loads. So if the receiver is only rated for 8-ohms, you will have to use speakers with a nominal 16-ohm impedance rating.
Regards,
Wayne A. Pflughaupt
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