# bridged mono?

Discussion in 'Amps and Cabs [BG]' started by ThatOneGuy, Feb 27, 2004.

1. ### ThatOneGuy

Jan 2, 2004
Oregon
I'm sorry if this is a dumb question, but its really been bugging me. What is bridged mono? and what kind of cabs do you need to use it? (i.e. what impendance, how many cabs).

2. ### nashvillebill

A mono amp is an amp that only has one output channel. A stereo amp has two output channels, each can be indpendant. Then somebody figured out that if you take a stereo amp, and run the same signal through both sides, but invert the signal on one of the channels...then if you hooked a speaker up between the positive terminal of channel A and the positive terminal of channel B, you'll get the combined power of both channels. One output, but "bridging" the two power amp channels. If each side can put out 400 watts into 4 ohms, bridging into 8 ohms will put out 800 watts.

Of course, there's no such thing as a free lunch. First, the amp's circuit must be designed so that the two channels signals can be inverted and the two output channels can be hooked up in this configuration. Second, the allowable impedance will now be the sum of the two channels impedance. Suppose the amp can only run a 4 ohm speaker in channel A or Channel B, and isn't capable of running a 2 ohm speaker load in either channel. If running in bridged mode, the speaker impedance can't be any lower than (4+4) which equals 8 ohms. You could use 1 speaker (at 8 ohms), or 2, or 4, or 10, as long as the total impedance of these combined speakers doesn't go below the minimum allowable of 8 ohms for the bridged mono operation. The better amps will be capable of a bridged operation into a 4 ohm load, but many amps can only bridge into 8 ohms (if they can be bridged).

3. ### ThatOneGuy

Jan 2, 2004
Oregon
Hey thanks alot Bill! That makes senes now.