Klas, you wrote:
> Hmmm.. there are very few "fully balanced" microphones today. Most of
> them, even the MKH series for example, (and R=F6de NT1A) have pin 3
> just AC grounded. So oscillation occurring internally in the mic,
> will go straight into pin 2 and never get outbalanced.
Are you sure? As far as I know, all common phantom-powered microphones
provide a balanced output. I just googled for microphone circuits and
found this very interesting page that exlains the principle of the MKH
microphone series:
http://www.beis.de/Elektronik/HF-Mic/HF-Mic.html
I admit that it is quite difficult to fully understand that circuit.
Though, it is clear that pin 3 is not AC grounded!
> The only way I know that mic electronics can make an unclean phantom
> power even worse, is when something in the circuit starts to
> self-oscillate. But such an oscillation is easy to see on the scope.
> And the PRO6 handle is actually only a simple filter and source
> follower!? Quite conventional and fully established.
> And why shouldn't PRO6 work with a semi-pro machine like the Fostex,
> when it works fine with a cheap consumer machine like the Zoom H4??
Is pin 3 of the PRO6 really AC grounded? If so, this unusual
asymmetric design could be the reason for the problems with some
recorders. As I mentioned before, a microphone that provides
complementary AC output signals on both pin 2 (+) AND pin 3 (-),
should be less demanding regarding any potential phantom power noise.
If you use an asymmetric design, there should be no AC grounding on pin 3!
Regards,
Raimund
http://www.avisoft.com
|