Post by Dori-Kin on Oct 1, 2006 13:12:08 GMT 7
When you're told a stereo power amplifier can be bridged, that means that it has a provision (by some internal or external switch or jumper) to use its two channels together to make one mono amplifier with 3 to 4 times the power of each channel. This is also called "Monoblocking" and "Mono Bridging".
Bridging typical HIFI amplifier involves connecting one side of the speaker to the output of one channel and the other side of the speaker to the output of the other channel. The channels are then configured to deliver the same output signal, but with one output the inverse of the other. The beauty of bridging is that it can apply twice the voltage to the speaker. Since power is equal to voltage squared divided by speaker impedance, combining two amplifiers into one can give four (not two) times the power.
In practice, you don't always get 4 times as much power. This is because driving bridging makes one 8-ohm speaker appearing like two 4-ohm speakers, one per channel. In other words, when you bridge, you get twice the voltage on the speaker, so the speakers draw twice the current from the amp.
Another interesting consequence of bridging is that the amplifier-damping factor is cut in half when you bridge. Generally, if you use an 8-ohm speaker, and the amplifier is a good amp for driving 4-ohm speakers, it will behave well bridging.
Also consider amplifier output protection. Amps with simple power supply rail fusing are best for bridging. Amps that rely on output current limiting circuits to limit output current are likely to activate prematurely in bridge mode, and virtually every current limit circuit adds significant distortion when it kicks in. Remember bridging makes an 8-ohm load look like 4 ohms, a 4-ohm load look like 2 ohms, etc.
If your amplifier does not have built-in bridging option built in you can use an additional stage to invert the signal for one channel but drives the other channel directly.
Bridging typical HIFI amplifier involves connecting one side of the speaker to the output of one channel and the other side of the speaker to the output of the other channel. The channels are then configured to deliver the same output signal, but with one output the inverse of the other. The beauty of bridging is that it can apply twice the voltage to the speaker. Since power is equal to voltage squared divided by speaker impedance, combining two amplifiers into one can give four (not two) times the power.
In practice, you don't always get 4 times as much power. This is because driving bridging makes one 8-ohm speaker appearing like two 4-ohm speakers, one per channel. In other words, when you bridge, you get twice the voltage on the speaker, so the speakers draw twice the current from the amp.
Another interesting consequence of bridging is that the amplifier-damping factor is cut in half when you bridge. Generally, if you use an 8-ohm speaker, and the amplifier is a good amp for driving 4-ohm speakers, it will behave well bridging.
Also consider amplifier output protection. Amps with simple power supply rail fusing are best for bridging. Amps that rely on output current limiting circuits to limit output current are likely to activate prematurely in bridge mode, and virtually every current limit circuit adds significant distortion when it kicks in. Remember bridging makes an 8-ohm load look like 4 ohms, a 4-ohm load look like 2 ohms, etc.
If your amplifier does not have built-in bridging option built in you can use an additional stage to invert the signal for one channel but drives the other channel directly.