In addidtion to what the article says, there is also amps that has balanced output, which would mean neither leg of the speaker connector is at ground. You get the same result from bridging an amp and running it from a balanced input.
Some pro amps have balanced outputs as well as inputs, for the purpose of sending the incoming signal to another amplifier. But I get the feeling that is not what you are talking about…
Perhaps you could clarify what you mean about the balanced outputs and speaker connectors at ground. Also, “You get the same result from bridging an amp and running it from a balanced input.” Neither make any sense.
I meant a fully balanced amp from input to output like the Krell FPB utilizing the balanced input stage would be effectively the same as bridging 2 channels of an amp and
using the balanced input again.
That is why you can't bridge a Krell FPB amp, it is bridged already.
I guess if you use the RCA input, you are not feeding the amp a balanced signal, requiring the amp to have a phase inversion stage for the other half of the balanced amplification stages.
Can't be sure if all amp utilizes fully balanced input to output when bridged, or they just get reconfigured to run a balanced output stage.
Balanced output is same as bridging, where the negative connector is not at ground. It is a hot connection with the opposite phase as the positive connector.