Dan Dugan <> wrote:
>
> > Yep, the 48 V phantom power scheme is actually a huge waste of energy. =
Assuming that the 48 V phantom power voltage provided by the recorder is re=
gulated down to 5 V inside the microphone, then only about 10 % of the prov=
ided energy is actually used to power the microphone. The other 90% is just=
converted into heat...
>
> Only if a shunt regulator is used. A series regulator will waste a lot le=
ss, won't it?
>
> -Dan
Yes, this is true for most cases in regulators for multi-purpose use. But i=
f one exactly knows the current that will be drawn (which should be the cas=
e in a microphone) then the shunt resistor can be optimized in such a way t=
hat there is no additional waste of energy.
In any case, if you need to convert a voltage from 48V down to 5V (without =
a clocked DC/DC converter), then the smallest possible wasted power can sim=
ply be calculated by multiplying the current draw by the voltage drop (the =
power that actually operates the microphone is equal to the remaining volta=
ge multiplied by the current draw).
So, in a phantom power circuit with a microphone that is internally operate=
d at a voltage of 5V, at least 90% of the supplied energy is converted into=
heat along the series resistors.
Regards,
Raimund
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