Although cable capacitance is not an issue with low-Z mikes, Pro-Co Sound
claims that series inductance is an issue. Quoting from
http://www.procosound.com/downloads/mic_guide.pdf


"While parallel capacitance, the enemy of highfrequency
response in high-impedance instrument cable, is largely insignificant in
low-impedance applications,
series inductance (expressed in microHenries, or uH) is not. The inductance
of a round conductor is largely
independent of its diameter or gauge, and is not directly proportional to
its length, either. Parallel inductors
behave like parallel resistors: paralleling two inductors of equal value
doesn't double the inductance, it halves it.
In cable construction, using two 25 AWG conductors connected in parallel to
replace each of the conductors of
a 22 AWG twisted pair will result in the same DC resistance, but
approximately half the series inductance. This
will result in improved high-frequency performance: better clarity without
the need for equalization to boost
the high end."

I cannot dismiss this, which is why I seek your opinions. I do note,
however, that the article does not appear to distinguish between
self-inductance and mutual inductance. As far as I can see, the only valid
way to measure inductance of a mike cable is to shortk a signal pair at one
end, and measure the mutual inductance from the other end. Has anyone done
this, or performed any quantitative measurement?

The article continues to discuss skin effect, which has been generally
rejected in previous discussions as irrelevant to audio quality. I would
appreciate an analyis of the below statement:

"The phase lag caused by skin effect is one radian (about 57.3 degrees) per
skin depth, and the effective skin
depth of a conductor at a particular frequency is the same whether the
conductor is very large or very small in
diameter. For instance, the skin depth of a copper wire at 20 kHz is about
..020 inches, while an 18 AWG conductor
has a diameter of about .040 inches. This means that at frequencies from DC
to 20 kHz, the full cross-sectional
area of the conductor is utilized. Because the skin depth (.020") is never
less than half the diameter of the
conductor (.040"), there is never more than one radian of phase shift
present.
In short, star-quad cables seem to offer lower inductance and lower phase
shift, both of which are parameters
that directly affect the clarity and coherence of high-frequency complex
waveforms. Their inherently superior
noise-rejection also reduces intermodulation distortion, a type which is
particularly offensive because it produces
"side-tones" not harmonically related to the fundamental. While the
improvement may not be as dramatic as
changing the microphone, an increasing number of audio professionals seem to
be embracing the sonic benefits
of star-quad construction."

The article also dismisses the construction of the "premium line"
Audio-Technica mike cable,
http://www.audio-technica.com/cms/ca...f2c/index.html , which
consists of separate spiral-wrap shields for each conductor. Each conductor
is additionally coated with conductive carbon impregnated vinyl. Although
A-T claims this is to reduce handling noise (which Pro-Co dismisses), it
appears that it may also serve as a high frequency shield, supplementing the
spiral wrap.

It would seem that the separate shielding of each conductor in the A-T cable
somewhat increases the spacing between the two conductors, which might
harmfully increase the mutual inductance. Opinions?

Manufacturers claim star-quad is an unqualified improvement. Rec.audio.pro
opinions tend more to the pov that star-quad is a problem solver for
difficult EMI situations, which are largely peculiar to television studios
and secondarily, public performance spaces. Does anyone have any
quantitative measurement that would help resolve this?

"Robert Morein" wrote in message
...
Although cable capacitance is not an issue with low-Z mikes, Pro-Co Sound
claims that series inductance is an issue. Quoting from
http://www.procosound.com/downloads/mic_guide.pdf


"While parallel capacitance, the enemy of highfrequency
response in high-impedance instrument cable, is largely insignificant in
low-impedance applications,
series inductance (expressed in microHenries, or uH) is not. The
inductance of a round conductor is largely
independent of its diameter or gauge, and is not directly proportional to
its length, either. Parallel inductors
behave like parallel resistors: paralleling two inductors of equal value
doesn't double the inductance, it halves it.
In cable construction, using two 25 AWG conductors connected in parallel
to replace each of the conductors of
a 22 AWG twisted pair will result in the same DC resistance, but
approximately half the series inductance. This
will result in improved high-frequency performance: better clarity without
the need for equalization to boost
the high end."

I cannot dismiss this,

By now, you should.

I think that several have already pointed out that moderately long mic
cables (100s of feet) just aren't a problem, and that in use, mic cables
tend to perform about the same.

The most obvious performance characteristic of mic cables is simple
integrity. Mic cable is fairly well standardized, as are the connectors. The
major controlling factor is quality of assembly and soldering.