Re: Boxing the compass....

In article <46rpvtFcob3jU1@xxxxxxxxxxxxxx>, Eiron wrote:
Negative feedback flattens the frequency response and reduces distortion, which
is usually regarded as a Good Thing. It also makes the whole design much more
controllable, as the gain of an amplifier with NFB will be determined only by
the feedback components and not the amplifying devices themselves. In fact, the
open loop gain of most amplifying devices is such that without feedback they
wouldn't be amplifiers at all, but oscillators.

Most amplifying devices can't oscillate without feedback.
Without feedback they would have very high gain, limited bandwidth, and probably
be stuck at one or other of the supply rails.

Point taken. I meant to say that without *negative* feedback most of them would
oscillate. Perhaps I should have made this clearer.

Have you ever tried removing the negative feedback from an audio amplifier? It isn't
always possible to isolate the feedback path from DC bias, depending on circuit
design, but sometimes it is. Some valve designs used a small winding on the output
transformer for example. If you do feel like trying this, I'd suggest you connect
the amplifier to a dummy load consisting of a big resistor on a heatsink, rather
than your best loudspeakers.

Rod.

.

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