Hi Raimund,
At 05:58 PM 2/8/2011 +0000, you wrote:
>Yes, this is true for most cases in regulators for multi-purpose use. But=
>if one exactly knows the current that will be drawn (which should be the
>case in a microphone) then the shunt resistor can be optimized in such a
>way that 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
>simply be calculated by multiplying the current draw by the voltage drop
>(the power that actually operates the microphone is equal to the remaining=
>voltage multiplied by the current draw).
>
>So, in a phantom power circuit with a microphone that is internally
>operated at a voltage of 5V, at least 90% of the supplied energy is
>converted into heat along the series resistors.
But this is only half the efficiency picture, don't forget, if using 48 V
Phantom power from a recorder, this 48 V power has to be generated by
another circuit in the recorder ahead of the microphone by using an
inverter to raise the 5-6VDC recorder battery voltage to 48 VDC so in
truth, you have a double efficiency whammy, first in the recorder
generating the 48 V to send sdown the cable, and then in the microphone to=
regulate the 48 down to 5 volts or less, sometimes 3 VDC to power the mic
preamp...
Why do we endure this double whammy? Because of cable loses, by sending a
high voltage down the cable and regulating it at the mic end supposedly
overcomes long run cable loses...
Hence for the sake of efficiency, it is far better to have a battery/power=
source at the microphone as I see it and eliminate the double conversion
process which is more battery hungry that the recorder itself... And this=
proves true according to my own experience...
--
Thanks,
Mitch & Shadow...
http://www.4shared.com/dir/UTASxktL/wildlife.html
Shadow's area: http://www.4shared.com/dir/ecfWjyZb/Shadow.html
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