loudspeaker fuse

The loudspeaker protection circuit described elsewhere in this issue can be used to protect multipath loud- speaker systems effectively from users with destructive tendencies. It can be done even more simply by using an old-fashioned glass fuse in series with the loudspeaker wiring. The melting value (in A) of the fuse is based on a compromise between a high value for the bass speaker, a less high value for the medium range and a low value for the treble speaker. To place the fuse in series with the loudspeaker wiring (figure 1) as it stands would cause considerable problems. This is because a fuse has a relatively high series resistance. It is not too good for the muting factor of the amplifier or for the bass reproduction quality for that matter. 80555 - 1 But there is more to it. When a current passes through the fuse it gets hot causing non-linear thermal behaviour — and the quality of the bass will show a negative temperature coefficient. Something can be done about this. I...