Originally Posted by danielo
So differential tells us something about the input side of things and how the resulting bridge is done. For the first time it at least makes sense to me can someone confirm this for me ?. Also that would mean that any differential amp has to be internally bridged no ? How else is it differential if the neg and pos are not amped by themselves ?
Let's divide and conquer. When talking about bridge amps, you can always think about it as two amplifiers driving one speaker. That never changes under the hood.
So all we have to consider is how those two amps get their respective input signals. They can be from:
a) two single-ended inputs (rare)
b) one single-ended input
c) one differential input
Let's take them one at a time:
a) This is the conventional stereo amp. Unless there is an external device used to invert the signal to one channel, it cannot be used in a bridge application.
b) This would include amps with "bi-amp" switches, be they home or car amps. The single-ended input feeds the positive amplifier directly. The same input signal feeds a unity-gain inverter, and that feeds the other amplifier for the negative output.
c) Differential input amps can be just like case a) except with a "differential" input jack added. More below.
single in bridged = signal is not balanced coming in and split and flipped before bridged
balanced in bridged = signal can stay differential and is bridged right away. The 2 signals never touch until the speaker(s).
Yes, it's possible. But if the balanced source carries different audio levels, which is permissible in perfectly balanced audio (it's about the impedances, not the audio), then the amplifier will not reach its full output potential. Also, if the two amplifiers are not perfect (identical) in how they handle the interference noise imposed on the input connections, it may not cancel fully across the speaker terminals--degrading common mode rejection ratio. For both reasons, it might be safer to convert the balanced input to single-ended just as the audio enters the amp, be it by transformer or proper balanced to single-ended converter. Then go about treating that signal the same as any other bridge amp.