One of the most frequent questions we get is the difference between stereo, parallel, and bridge mono modes in Amplifiers
Stereo operation mode is the normal, default mode of an amp. This means that the amplifier provides power to two independent channels. Think of it as two amps in one. Many recent amps can even run two different power/resistance ratings on the two channels at the same time. Usually we run two outputs (left and right) from a mixer, into the two amp channels (left and right), and then into two speakers set up in front of an audience, one on the left, one on the right. This enables an audience to enjoy the stereo effects of music.
Parallel operation routes an identical audio signal of one amp input into both channels. You use this to route a mono input (like a microphone, or mono output of a mixer) into both channels of an amp. It is the same as using a Y cable to split a mono input into both channels. After the input, the amp acts exactly like a stereo mode amp.
Bridge Mono Operation
Bridge mono mode combines two amp channels into one mono, much more powerful amp channel. This is most often used for subwoofers. Amplifiers have separate stereo and bridged mono power handling specifications. For instance, the Alto MACRO 1400 amp is rated at 310 W at 8 ohms STEREO, and 900 W at 8 ohms BRIDGE MONO. The advantage of bridge mono is that you have a much higher power rating; the disadvantage is that you have only one amp channel.
Connecting speakers to an amp in bridge mono mode is different from stereo mode. Usually you connect a banana plug to the middle two banana outputs. You must also flip the amp into bridge mono mode, using dip switches on the back of your amp. Consult your amp manual for specific directions on your particular model.