[Phil Allison[_4_]]

wrote:

I just bought a used 100 foot snake.

I was surprised at the configuration.
It has 2 pair of heavy wires designated as speaker 1 and 2.

I had always though that running amps of current through a cable parallel
to mic cables would magnetically induce unacceptable amounts of crosstalk
into the mic cables.

So I ran a test.


** Can you detail how you did that?

Were mics connected to the balanced lines ?


There was some measurable crosstalk but is was surprisingly low. Low
enough that if the mic and speaker are in the same room, acoustic
feedback by far dominates the electrical feedback caused by the crosstalk..

So it seems this is a usable configuration.

Does anyone have experience with snakes of this configuration?


** In a portable PA system, this can be risky when you allow for simple mistakes made during set up. The risk is supersonic oscillation, induced by crosstalk.

Running balanced and speaker lines tied together is commonly done with amp racks. It works fine until someone powers the rack up without connections being made at the far end of the cables and advances the amp gain controls. The unterminated balanced line couples capacitively to the hot speaker wire and oscillation is possible. Usually at a frequency like 50 or 100kHz.

The risk is higher if you are using a powered desk since so much more gain is available.



..... Phil