As a general rule using a battery box on the mic input is not really a good idea.. but it should not be a problem as long as the person who built the battery box has built it correctly
And plugging in a battery box backwards into a powered mic input can have really bad results for the power supply of the device your connecting it too... Yet another reason why its not a good idea. Its like Ghost busters when they crossed the streams sure they could do it but it was still not a good idea.
I think a lot of people may be getting confused. Very confused.
Let's hope the battery boxes are wired correctly, but are they REALLY sending their power to the recording device or to the microphone? My experience has been that the battery box increases the effectiveness of the microphone into "Mic In" -- more signal, depth and performance.
It is my understanding, from microphone manufacturers, that supplying voltage to their microphones is good, but not a replacement for a pre-amp.
If you think otherwise, please say so clearly. Explain the circumstances and battery boxes you think enable a microphone to become "Line In" enabled. I know of NONE.
Check out Giant Squid Audio...they make little custom mics like Church Audio. The developer has told me that supplying, for example, +48v to his mics would "fry" them. His 9v battery box does a good job of increasing the signal to "Mic In" but does nothing for "Line In."
At the same time, he doesn't assert that a battery used to increase the performance of the microphone will approach a pre-amp in any way -- meaning it's not, NOT ready for Line In.
http://www.giant-squid-audio-lab.com/gs/gs-micline1.htmlI have used the H2 with Mic In, I have used it with Line In when using the Shure FP23 pre-amp. The signal through the pre-amp is wholly superior. But for a $200 recorder to use a $400 pre-amp is not cost-effective, IMHO.