Phantom Power +15V vs +48V for AT4040

[bgavin]

My Rane preamps provide +15v phantom power. The specs for my AT4040 are 48 volts.

Question: what is the impact of using my AT4040 with the +15v provided by my Rane preamps?

 

[Sklathill]

It's a true condenser that requires 48 volts. Some AT mics are electrets (some of the 30 series) and are fine at 15 volts. This is not one of them.

As for impact...well, I've only experienced where the phantom was a bit below spec, say, in the 30s. Depending on the mic, it might not work and just sound very crappy, or it might not work at all. I know some mic manufacturers make special high-voltage versions of their mics and the thing they promote most is extra SPL handling...

 

[bgavin]

I was doing some more digging and came up with this quote from Rane Tech Note $148:

There is a huge myth circulating that microphones sound better running from 48 volts, as opposed to, say, 12 volts, or that you can increase the dynamic range of a microphone by using higher phantom power.

For the overwhelming majority of microphones both of these beliefs are false. Most condenser microphones require phantom power in the range of 12-48 VDC, with many extending the range to 9-52 VDC, leaving only a very few that actually require just 48 VDC.

The reason is that internally most designs use some form of current source to drive a low voltage zener (usually 5 volts; sometimes higher) which determines the polarization voltage and powers the electronics.

The significance is that neither runs off the raw phantom power, they both are powered from a fixed and regulated low voltage source inside the mic. Increasing the phantom power voltage is never seen by the microphone element or electronics, it only increases the voltage across the current source.

But there are exceptions, so check the manufacturer, and don't make assumptions based on hearsay.