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46
APPENDIX C: BALANCED LINES,
PHANTOM POWERING, GROUNDING
AND OTHER ARCANE MYSTERIES
What is it, exactly?
The obvious external power source for any
modern microphone is a battery. About the only
electronic advantage that a battery has is that
its output is pure DC. The only other advantage
is to the battery company — you have to keep
on buying them.
Tube microphones require several different
voltages for operation. This invariably means a
multi-conductor cable and non-standard (not
XLR) connectors. A tube microphone will always
have an associated external power supply.
In the late 1960’s, Neumann (you know, the
folks that brought you the U47 and U87
microphones) converted its microphones to solid-
state, adopting a system of remote powering that
they called, and trademarked, Phantom Powering.
Because of the trademark, some manufacturers
use terms like Simplex Powering, etc. Over the
years, the trademark has become genericized and
now refers to any device that is powered accord-
ing to DIN standard 45 596 (or maybe it’s DIN
standard 45 595, we’re not exactly sure…).
So, why “Phantom” Powering? Because (like
the Phantom in the old comic strip) it’s there
when you need it, and invisible when you don’t.
This technology is not new; it actually predates
rocket science. Like many other things in au-
dio, it was brought to you by the telephone
company, who used it to get an extra circuit
from a pair of wires. In effect, so does your
phantom powered microphone.
What is important is: phantom powering is
a compatible system. Your dynamic/ribbon
microphones as well as your condenser
microphones work side-by-side, from the
same microphone inputs, without further
thought on your part.
Technically speaking, phantom powering refers
to a system where the audio signal is applied
to the balanced line in differential-mode, and
Balanced Lines
Balanced lines offer increased immunity to ex-
ternal noise (specifically, hum and buzz). Because
a balanced system is able to minimize noise, it is
the preferred interconnect method, especially in
cases where very long lengths of cable are being
used. A long unbalanced cable carries with it more
opportunity for noise to get into a system —
having balanced inputs means very little noise
will enter the system via snakes and other cables
that typically must run a long length. But regard-
less of length, balanced lines are best.
Phantom Powering and Microphones
History
Condenser (capacitor) microphones differ
from dynamic and ribbon microphones because
they are not self-generating. That is, they cannot
generate electricity in response to an impinging
sound wave. A condenser microphone modifies
an external source of electricity to reflect the
effects of a sound wave striking its diaphragm.
Dynamic and ribbon microphones use magnetism
to generate electricity in response to a sound wave:
they are self-generating. Furthermore, both of these
types of microphones are inherently low-impedance
devices. It is possible to connect a dynamic micro-
phone element directly to a balanced, low-
impedance mixer input. Many commercially
made dynamic microphones do just that.
On the other hand, a condenser microphone
is an inherently high-impedance device. How
high? Verrrrrrry high. On the order of a billion
ohms (1 Gigaohm). This is high enough that
the inherent capacitance of a foot of shielded
cable would audibly reduce the output of the
microphone. All condenser microphones have
an impedance converter, in the form of a
vacuum tube or field-effect transistor (FET),
built into the microphone and located ex-
tremely close to the microphone element. The
impedance converter and the microphone ele-
ment itself require an external power source.
1
1
To be strictly correct, electret condenser microphones are
a bit different, as the microphone element does not require a
power source for operation (it is more or less permanently self-po-
larized). Regardless, the impedance converter still requires an
external source of power.