Bridged mono, the correct way?

[theAnonymous1]

This dilemma has plagued my thoughts for some time now. What is the "correct" way to feed a signal to a stereo amplifier to end up with a bridged mono output?

1) Left channel to one half of the amp, and right channel (inverted) to the other half?

2) Sum the left and right channels, sending an inverted signal of their summed outputs to one half of the amp and non-inverted to the other?

 

[paulb]

1. (L) - (-R) = L+R
2. (L+R)-(-(L+R)) = 2L+2R
Looks like you get more gain the second way, assuming you can sum to mono without any loss. What do you mean by "correct"?

 

[theAnonymous1]

Ah, well..... I should have explained my thinking more clearly.

My thinking was (is), a stereo source doesn't always have the same information in both channels. So with option 1, if there is only information in one channel, there will only be half(?) the gain in the amp output when compared to option 2.

So unless my logic is failing me, option 1 would act more like two individual sources gain-wise, and only output the same gain as option 2 when both channels are correlated.

Am I making any sense?

 

[Xoc1]

Both will work and give the same output signal, once you have adjusted the gain.
Summing the left and right channels and then inverting one channel before the amplifier will ensure maximum power before clipping which may be important to you.

 

[theAnonymous1]

I see the flaw in my thinking now.

Option 2 will also have less gain if only one channel is playing, but it still has a higher overall gain than option 1.

I think I will go with option 1 though, as it will still allow me to use the amp in stereo by simply inverting the speaker leads on one channel (also easier on the power supply?).

Thanks!