:wave Bridging an amplifier allows you to "short" the two channels of your amplifier together into one output channel, essentially turning a two-channel amp into a one channel amp. Not all amplifiers are capable of being bridged, and those that are will have minimum speaker impedance and connection requirements.
The goal of bridging a stereo amplifier is to have one channel with greater (usually about double) power output than the amp provides into two channels. In order to bridge an amplifier it must have at least two channels and it must be capable of being bridged. Check your amplifier's owners manual to see if you can be bridged. Also, amplifiers capable of bridging will have a switch somewhere on the rear panel labeled "bridge" or "bridge mode" or "mono" or something similar.
After doing those things, you STILL have to be careful. By bridging an amplifier you essentially halve the impedance it "sees" from a speaker. So an 8 ohm speaker behaves like a 4 ohm speaker to the bridged amp. Be sure your amplifier is capable of delivering consistent power into the lower impedance without overheating or distorting before going through with the bridging process.
Many times, its better to simply buy a more powerful amplifier, rather than operate two different ones in bridge mode. Bridged amps usually run hotter, and excessive heat is the enemy of every stereo component.
how to bridge an amp
All you gotta do is take the positive from the left channel speaker output on the amp and hook it up to the sub's positive wiring terminal, and then the negative from the right channel speaker output on the amp and hook it up to the sub's negative wiring terminal. Just leave the left negative and right positive amp speaker terminals alone as they are not needed.
if your using this for a sub....
make sure the sub is not a DVC model (two pairs of terminals on one sub), then you can bridge bridge the amp and it will still get a 4-ohm mono load because you only have one subwoofer.
hope this helps
-Motts