In article , Don Pearce
wrote:
On Mon, 29 Nov 2004 13:55:30 +0000 (GMT), Jim Lesurf
wrote:

Following on from some discussions in other threads I couldn't find any
existing data on the resistance-current properties of fuses, so did a
quick measurement as a simple experiment.

The results are shown on the graph at

http://www.st-and.demon.co.uk/temp/fuseplot.gif


[snip]

Jim, for the purposes of seeing how a fuse might affect linearity, some
sort of frequency response of resistance change vs frequency would be
needed. If a fuse has a very low thermal inertia, it might change its
resistance significantly during a cycle, particularly at low
frequencies. This would cause distortion if it was in series with a
speaker.

Yes, I'd agree this may well be so, particularly for LF or LF+HF intermod
effects. Not seen measurements, etc, on this. But I avoided using o/p fuses
in the past precisely because I feared such things might occur.

At higher frequencies which it could not track, it would simply
cause amplitude compression - I've used a light bulb for this in the
past.

Yes. In fact IIRC some of our older sinewave oscillators in the teaching
labs use a small incandescent lamp to stabilise the gain of the oscillator.
(That makes me also recall that I think the old 'Sound Technology THD
analyser I used to use also did something similar.)

Slainte,

Jim

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