bridged amps and external crossovers

[zaphod]

read a throwaway line in another forum about how bridged amps cannot be used with external active crossovers.

anyone know about this?

 

[tsv_1]

read a throwaway line in another forum about how bridged amps cannot be used with external active crossovers.

anyone know about this?

Had to have been a special case. There's no reason why a pre-EQd audio signal can't be fed to a bridged amp (or amps). The only gotcha with bridged amps (assuming they are designed to operate properly in bridged mode) is that the "-" terminal to the speaker can't be connected to GND. That's it AFAIK.

 

[MPS]

There is no way for the active x-over feeding the signal to know whether the amp is bridged or not. Bridging only controls the output stage of the amplifier.

 

[tsv_1]

There is no way for the active x-over feeding the signal to know whether the amp is bridged or not. Bridging only controls the output stage of the amplifier.

I'm not arguing... just want to fully flesh out the concept of bridging since it actually does involve both the input stage(s) and output stage(s) of the target amp. While it's true that the input stages between the two halves are independent, the signal fed to them gets some special treatment.

Bridging is when an audio signal is phase-split to derive a zero-degree version and a 180 degree version of the same signal. The zero-degree signal is fed to one amplifier, while the inverted version is fed to the mirror amp (usually these two amps are within one chassis as part of a stereo amp, though not exclusively).

Then the "+" output of the first half of the amp (the one that amplified the zero-degree version of the signal) is connected to the "+" input of the speaker. The "+" output of the second amp is then connected to the "-" terminal of the same speaker. And Voila - one amp is essentially delivering current at a given phase, while the other is sinking that current... then vice versa as the signal drops below whatever bias point has been set up.

At least this is the classic method for bridging... but this is 2011, so maybe there are now more ways to skin this kitty.

 

[Tj Bassi]

Never heard of the crossover thing, but be careful about the load (impedance) you are running into when bridging amplifiers. Each amp sees half of the normal unbridged load, or puts out twice the current, which ever way you prefer to look at it.

Tj

 

[zaphod]

thanks guys, it didn't add up to me either, but i don't have the electronics background to know for sure. I need to chase down where i read this (any number of audio forums ) and find out what made the poster say what they did.

cheers