"Don Pearce" wrote in message

On Wed, 16 Jul 2003 06:57:55 -0400, "Arny Krueger"
wrote:

And of course everything, including the speakers themselves, is
inside the feedback loop.

Say what? To put speakers inside a feedback loop you have to
accurately sense their acoustical output in a timely fashion, and
that has always been a problem.

I'm talking about the speakers as electronic components. I don't mean
that the feedback includes the acoustic output - although to a limited
extent it does. The speaker terminals of an amplifier are within the
feedback loop, and anything connected there is within that loop.

I guess I was taught a narrow view of what is inside the loop. Clearly the
source and load impedance affect the operation of the loop, but the way I
was taught, they are not inside the loop.

That is why some designs are capable (hah!) of bursting into
oscillation if an inappropriate impedance is connected there.

The way I was taught, those would be called influences outside the loop that
affect how the loop operates. Other influences include EMI and the power
source.