Jon, on that circuit, how do you increase the polarizing voltage? Or make it exactly the same in two different mics?
After reading more, I think it may not be such a good idea to bypass the DC up converter, because there is no regulation if the phantom power source dips. When the phantom power voltage dips, it lowers the output of that FET. I'm convinced that there is something wrong with the DC converters in one of my mics. I read about someone else who had the same problem, 4 db less output from one mic. He bypassed the DC converter, and that fixed the problem, but he said the microphones output would ride up and down with the phantom power voltage.
One more thing...
I've read that 20-30v DC is normal for the polarizing voltage in the 603 circuit. I wonder if just matching the zeners between a stereo pair would be a good way to get equal voltage going to each mic? I hope that makes sense.