# Re: Roberts Gemini 49

"DAB sounds worse than FM" <dab.is@xxxxxxxxxx> wrote in message
news:7falvuF2k86fsU1@xxxxxxxxxxxxxxxxxxxxx

The context of the discussion is irrelevant. The claim you made was that
I'd made a mistake with my algebra, but in reality you didn't think about
the situation properly, or you simply didn't understand that it doesn't
matter whether you add or subtract a random signal.

The equations are as follows:

The signals received are: sum = L+R+n1, difference = L-R+n2

Left = sum + difference

Left = 0.5 * [(L + R + n1) + (L - R + n2)] = L + (n1 + n2)/2

Right = sum - difference

Right =0.5 * [(L + R + n1) - (L - R + n2)] = R + (n1 + n2)/2

You claimed that the + in front of n2 in the final equation was wrong, and
even after I'd explained teh maths to you you repeated that it was wrong.

You cannot now change the subject "because somethign else was being
discussed", because what was being discussed is irrelevant to whether the
equations are correct or not. This is maths, not the debating society.

Point out the error in my proof, or admit that you're wrong.

This *blatent* error in your "algebra" is *blisteringly* obvious to *anyone*
with even a basic understanding of all this.
The *error* is the final + in front of n2 in the final equation. It should
be a minus because, since L-R is subtracted to create R, then n2 - being the
noise present on L-R - is also subtracted to create R.
That's why n2 ends up being 180degrees out of phase between the two
channels, and that's why it totally cancels itself out when the L and R
channels are summed into mono.

I seem to recall saying this about a dozen times already, to a *total and
utter idiot* who still won't listen to reason, even when it hits him on the
head and then smacks him in the face.

You really are without clue, steven.

.