[Phil Allison[_4_]]

wrote:


** I should point out that supersonic oscillations, while inaudible, will destroy high frequency drivers and seriously damage most power amplifiers in a few seconds.


.... Phil

Yep, thats what I was worried about, the magnetic coupling between
the balanced lines has a high pass characteristic.


For the tests I ran, yes I had a mic connected and the other end connected
to a mixer. The crosstalk was not present with the mic disconnected but
was present with the mic connected. That makes sense that it is magnetic
coupling that needs a closed circuit. The mic pairs are electrostatic
shielded with foil so that should do a good job to drastically reduce
capacitive coupling, but no so effective for magnetic coupling. But still
the coupling is more effective at the higher frequencies so I was concerned
about ultrasonic oscillations.


** A lot depends on the mic pre-amps, usually they have good common mode rejection of low and mid frequencies diminishing at high and supersonic frequencies. They deal with supply frequency hum and harmonics well - but not so well with supersonics.



I get all the theory but practice and theory don't always agree, that's
why I am asking about real world experiences with these types of snakes.


** Other folks experience may have no relevance to to yours.
You need to be sure that YOUR set up is not susceptible to supersonic oscillation - or somehow, one day it will happen.


..... Phil