wrote in message
...
On Fri, 6 Feb 2004 21:07:45 +0100, "Meindert Sprang"
wrote:

wrote in message
.. .
On Fri, 6 Feb 2004 17:21:14 +0100, "Meindert Sprang"
wrote:
Based on what? Running a high powered amp without a proper load on it
can cause rapid failure.

Give me one reason why.... (audio amp, that is. HF/VHF is a different
story)


Heat

Please note that although a speaker is a dynamic load, it still has a
range of impedanve values as the voice coil moves. There are many high
powered amplifiers that MUST be used with speakers with a specific
nominal impedance or the amplifier will cook itself to an early grave.
This is particularly true of amplifiers that utilize fewer stages with
higher gain to achieve "good specs" at low cost. The typical
amplifiers used in mobile stereo systems fall into this category.

If an audio amplifier is not loaded with a speaker, it will simply not draw
more current than the quiscent current. It is a myth that an amplifier
should somehow overheat or whatever when it is not loaded. An amplifier act
like a servo system, due to it's feedback. This servo system tries to keep
the output voltage the same as the input * gain. This same system makes sure
that when the amplifier is loaded, more current is 'pumped' into the load to
keep the output voltage at the desired level. When the load is small, less
current is needed to achive that. When no load is present, no extra current
is needed that the quiescent current that flows through the output
transistors when in rest. When the load is too high, *then* you have a
problem when currents get higher that the transistors can cope with. That's
all there is to it.

Meindert