In article , Brian Gaff
wrote:
Actually, having read your piece, I suppose I should mention some other
things. Some of the edgy sounding amps in the 70s were often due to
dodgy filtering from what I could tell. Pioneer seems to suffer from
this problem.
I once had a Tandberg amp that really seemed able to drive almost
anything, and sounded crisp and nice. Problem was it picked up any RF
going and amplified it.. Not very practical.
That kind of thing is an example of why I and others came to regard it as
sensible to use passive RC filters on the inputs and output networks. It
not only helps define the maximum slew rate demanded of the amp. It also
helps prevent RF entering via input or output.
Tape, as I said in another response here had problems as it was
obviously impossible to record DC to a tape, so the flat tops were not
flat.
You did not cover this aspect, but when folk decided direct coupling was
a nice way to sell amplifiers, they used to show it with square waves
of course.
Yes. IIRC People like Harmon Kardon were keen on this and a 'dc to light'
approach. Not an approach I personally have been very keen on.
However, in air, you do not get DC, unless you cont the wind
as DC, but I've yet to see any speaker capable of a sustained draft!
Well the air *pressure* will certainly show variations with a spectrum well
below, say, 1Hz. But I'd agree that has little to do with normal audio
meant for human beings. :-)
So, integration will occur, thus the square wave is an input that cannot
be output in any case.
As the page (and your earlier posting) have already said, yes, you
inevitably have an upper limit and finite response time. The situation with
dc is less clear as you then end up worring about the meaning of 1/f noise
and how any level can be true dc if the universe only has a finite duration
of existence. However I thought that would be outwith the scope of the
webpage... ;-
Slainte,
Jim
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