Overview
Bridged or paralleled modes of working, normally involving audio power amplifiers, are methods of combining the output of two identical amplifiers to provide, what is in effect, a mono amplifier. Combining more than two amplifiers can be effected using the basic principles described, including the possibility of bridge and parallel modes in combination.
Two identical amplifiers are most often encountered in a common case, with a common power supply, and would normally be regarded as a stereo amplifier. Any conventional stereo amplifier can be operated in bridge or parallel mode provided that the common loudspeaker terminal (normally black) are connected and common to the ground rail within the amplifier.
Some two channel amplifiers, or stereo amplifiers, have the built in facility to operate in bridge mode by operating a switch and observing the input and output connections detailed on the back panel or in the manual. This option is most often found in high power PA equipment or amplifiers designed for car audio applications Operation in parallel mode requires no special facility and is implemented merely by the appropriate external connection.
Stereo amplifiers usually have a common control for gain and frequently bass/treble and when switched to bridge mode will automaticlly track each channel identically. Where two channel amplifiers have separate controls, and are switchable to bridge mode, only the controls on one channel will be operational.
Where the user implements his own connections for either bridge or parallel mode, and the amplifiers have individual controls, great care must be taken to ensure that both sets of controls are set identically.
Read more about this topic: Bridged And Paralleled Amplifiers