[Scott Dorsey]

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.

This is called a "powered snake" which seems like a bad description to me,
but that's what it is.

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.

It can. You don't have capacitive coupling so much to worry about because
the shielding is pretty effective against that, but you do have inductive
coupling especially at very low frequencies.

One of the tricks to dealing with this is cable twist, and having different
twist lengths on different cables (which cat5 cable does). If everything
is done just right, the inductive coupling on one twist is opposite polarity
from the coupling on the next twist and they all cancel one another out.

So I ran a test.

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.

I have seen some very crappy (and possibly damaged) powered snakes where there
was enough coupling to cause very low frequency motorboating on the amp.
Mike will know what I mean when I mention the old Adventure Theatre. But
I have also seen a lot more where everything worked just fine.

Does anyone have experience with snakes of this configuration?

Yes, they mostly work just fine. But, they are much less popular in the modern
age of powered speakers.

Also... don't use the speaker returns to run AC power to the board. I saw
someone do that once too. Interference resulted, and also the cable is not
rated for that.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."