Topic: Does phantom power 'usage' depend on the loudness of the sound source?

[su6oxone]

I'm no engineer, so please don't laugh if this is a ridiculous question.

I'm curious if the same 'amount' of phantom power (in terms of battery juice) is used when the mics are plugged in and recording ambient noise in my room versus when the same mics are recording a loud sound source.  The reason I'm asking is I'm wondering how accurately you can test battery life by just plugging in the mics at home (without any sound source) and recording until the battery dies.  I'm guessing it does not depend on the loudness of the source, so that testing battery life this way is pretty accurate (at least, until the voltage starts to drop and the mics' performance starts to drop).

[DSatz]

Not a ridiculous question at all! The phantom-powered microphones that I'm most familiar with (Schoeps and Neumann) use class-A bias in their output circuits, and thus draw the same current at all signal levels. I certainly don't know the circuit of every microphone in the world, but I've never heard of any phantom-powered microphones in which the current consumption varies with the output level. If it did, the supply voltage would vary along with it because of the resistance through which the powering is provided.

Again, that doesn't mean that it can't possibly happen--the IEC standard for phantom powering doesn't state that the voltage or current must (or in standards jargon, "shall") remain within any particular tolerance limit over time, for example. But some preamps with instrumentation-type input circuits might be upset by all the DC shifting that would occur, I would think.

--best regards

[su6oxone]

The phantom-powered microphones that I'm most familiar with (Schoeps and Neumann) use class-A bias in their output circuits, and thus draw the same current at all signal levels. I certainly don't know the circuit of every microphone in the world, but I've never heard of any phantom-powered microphones in which the current consumption varies with the output level.

As always, a privilege to get a definitive response from you Mr. Satz... many thanks!