BL> you'll perhaps see that your arithmetic really has nothing to

 BL> do with what Chris has in mind.



 RM> As far as I can see, a set of simple equations explains the

 RM> problem more concisely and clearly than any amount of blather.

 RM> I still don't get you. Please elaborate.



 BL>   Ask Chris. He now understands.



 BL>   If you stand a singer between two stereo microphones onstage, the

 BL> singer-signal at each microphone is almost the same in phase and

 BL> amplitide, and if you feed both into a differential amplifier they

 BL> cancel and the singer disappears. What Chris suggested was the

 BL> reversal of this, using a common-mode amplifier rather than a

 BL> differential amplifier! ROFL!



 BL>   This is plain silly. It's a howler! It the sort of thing a raw

 BL> beginner suggests. It sort-of makes sense if you don't think about

 BL> it... and you didn't think! It sort-of seems that common-mode is the

 BL> opposite of differential. What he wants is an amplifer that cancels

 BL> everything that isn't the same! ROFL!! You compare two signals and if

 BL> they're not the same they cancel! Just invert one side? ROFL!!



Let's compare the above bag of wind with this:



"Channel 1: A+B. Channel 2: A+C. To cancel out A, just subtract:

Ch1 - Ch2 = A+B - (A+C) = B-C. Easy. Now try to find an equation

that yields only A. Having trouble? All you get is combinations of

two or three (just as you did when you subrtacted the two channels)?

You'll find there is no way to extract any one of A, B, or C.

Situation hopeless."



Cheers



--- PPoint 1.88