Re: Making snake with D-sub connectors


ap wrote:
> I'm concerned about the uninsulated ground wires on each channel
> causing ground loops or possibly even total destruction.

Don't sweat it. Snakes, even microphone snakes, have been built from
multi-pair cable for generations. They work fine.

If you're using foil-shielded cable (OK for fixed installations), the
"grounds" are insulated becuase the foil is the inside layer, and the
outside of each pair shield is non-conductive. There's a drain wire
inside the foil wrapping in addition to the conductors, and that's what
you use to connect to Pin 1 or the chassis. Braided shielded cable
almost always has insulation over the braid for each pair.

While all the "shield" pins on the D-sub connector might (and in fact
should) be connected to the same point in the chassis, by connecting
each cable pair's shield wire to its provided terminal, you maintain
the shield continuity from unit to unit.

> If I run headphones from the same mixer as the mics, do they use the
> same ground?

Usually. Some people don't like to run headphone (or other line level)
signals through the same snake as the microphones because of the risk
of crosstalk between the high level signal and the low level mic
signal, however, with properly made cable, properly balanced outputs
and inputs, and proper wiring convention, this is rarely a problem.

> Any midi devices will be plugged into the same outlet as the mixer.

Now this is something that you should not run through the mic snake.
While 20 feet of cable in addition to your MIDI cables is not likely to
be a problem, you should be aware that there's an officially specified
maximum length for MIDI cable. I can't remember what it is, either 10
meters or 50 feet, probably, but there is low capacitance cable that
can extend the limit, so it's possible that nobody worries about it any
more. But it's a noisy signal with significant high frequency content.
It's prone to putting noise on the ground, so you should try to keep it
separately shielded and with a separate ground connection from the
mics.

.

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