On Mar 12, 9:36*pm, "Phil Allison" wrote:
"Robert Macy"
"Phil Allison"

** Co-ax works perfectly with microphones.

Every bit as good as shielded twisted pair cable.

Using physically realizable materials, the only signal carrying system
one can construct in a manner that will be the most immune to external
noise sources is a shielded balanced twisted pair system.

** *Fraid that is dead wrong.

Coax is prone to adding noise to the signal, since the
shield has impedance, carries the signal, and therefore can add noise
to the signal as the shield carries noise.

** Only true where the source has a common ground path with the receiving
device and an earth loop is created by the shield.

For a floating source, like a microphone, co-axial cable works just as well
as STP despite not being balanced.

This is not a very well known fact and derives from the inherent symmetry of
co-axial cable which rejects external magnetic field induction in a similar
way twisting a pair of wires does.

.... *Phil

Engineering's goal is to design a system until it is 'good enough' and
often, and in many applications and locations, coax can be
interchangeable with STP. Upon that premise I can agree with your
claim.

However, in general, STP will be better:
Floating mike, somewhat reasonable, except...
1 if a person holds the mike, there is a connection to 'gnd', which
creates a gnd loop.
2 if the shield is not terminated as a total and complete envelope
wrapped around ALL internals of the mike, there is unbalanced
capacitance, which allow noise sources to inject signals into
different circuit locations inside the mike. In other words, direct
pickup from those noise sources.