Many power amplifiers rate their maximum power output in watts, when operating in bridged mode. When an amplifier is bridged, its two output channels are combined into one. Rather than driving two speakers, the amplifier then drives only one speaker. The benefit of bridging a power amplifier is that in bridged mode, an amplifier's maximum power output is almost always more than twice its maximum output in two channel operation. bridged mode can, in fact, bring a three- or four-fold increase in power. Four channel power amplifiers can also be bridged; when bridged, four output channels will become two.
When bridging a power amplifier, it is important to first reference the amplifier's instruction manual and confirm that it supports bridged operation. Although most power amplifiers do support bridged operation, attempting to bridge an amplifier that does not support it can permanently damage it. Also, the power amplifier's instruction manual will almost always have a diagram explaining how it should be bridged. Always be very sure of what you are doing before attempting to bridge a power amplifier, and if you are not sure, call the amplifier's manufacturer to confirm. Bridging a power amplifier can be physically hazardous, as many power amplifiers are able to produce currents that are potentially lethal.
It is vital to bear in mind that the primary purpose of bridging a power amplifier is not simply to make the sound louder, although that certainly can be a result. The purpose is to drive speakers that the amplifier would not ordinarily be able to properly drive. For example, some public address speaker enclosures containing several small speakers might ordinarily not be able to be driven by a power amplifier running in two channel mode, but may work in bridged mode.
Examining the rear side of a power amplifier, at least two sets of speaker terminals should be seen, each having one positive post and one negative post. To bridge the power amplifier, the two leads coming from the speaker should be connected to the positive post on one amplifier channel, and the negative post on the other channel. In the case of Peavey power amplifiers, this process is made simpler by the presence of red speaker terminals. To bridge the amplifier, simply connect the speaker to the two red terminals. Additionally, a switch on the back of the unit will need to be flipped in order to enable bridged operation.
Bridging a Power Amplifier:
1. Confirm that the power amplifier in use is capable of bridged operation.
2. Be absolutely sure of the method for bridging the power amplifier that is in use before beginning.
3. Use extreme care, as an amplifier in bridged mode is producing potentially hazardous currents.
4. Before bridging an amplifier to correct a volume issue, confirm that a different amplifier or speakers would not in fact be a better solution.
5. Bridge the amplifier by connecting the speaker to the positive speaker terminal on one channel, and the negative terminal on the other.