<<Am I correct in assuming hiss is a product of the microphone?>>
Hiss exists in all electronic circuits, and is a product of random
fluctuations of electrons in conductors. The microphone will be the
noisiest part of a recording system, but any gain stage (transistor,
tube or opamp chip,) will greatly amplify the noise originating in all
preceding parts of the circuit.
<<Do mics become more prone to hiss with age, humidity, low phantom
power or low battery power.>>
Mics can change their sonic characteristics with age. Failing
capacitors will definitely add noise to the circuit. My experience
with humidity & condenser mics is not one of added hiss, but rather a
constant random popping as the polarization voltage arcs between the
front & back plates. Some mics which can run on battery power in
addition to phantom power are noisier on the lower voltage. In my
experience with Neumann mics the noise level is constant but the
dynamic headroom is severely degraded at voltages under the specified
48 volts.
<< Can faulty cables between the mic and the recorder increase the
level of hiss.>>
Not really. Cables have a simple job. They merely need to conduct. A
faulty cable will generally simply fail to pass signal. It's possible
that a corroded or tarnished plug will create a high resistance
connection, causing signal level to drop, but still pass. The
resultant increased gain further down the path will boost the inherent
noise of the circuit, but the cable itself isn't really generating any
additional hiss.
<< Should mics be returned to the maker after some years for
maintenance.>>
Only if there is audible degradation. Microphones as much as 60 years
old are in constant use in major studios throughout the world. They
change over time, but not necessarily in a fashion which is considered
worse. Anything with capacitors in circuit degrade & need maintenance,
but this might mean at 20 or 30 year intervals. Send them in to the
manufacturer if you feel you're not getting what you formerly were
hearing with the mic.
<< I use Senheiser and Rode mics. Any suggestions or advice on how to
reduce hiss would be very welcome. I have a built in Hiss filter as my
hearing cuts off at 5KHz but the hiss degrades recordings for others.
Stuart.>>
The self noise of the mic is pretty much a given, although there are
some people who modify circuits to improve performance. In microphones
this usually results in better transparency, but it's not unlikely
that some small improvement can be made in the noise spec as well,
depending on the mic. Audioupgrades.com in Southern California is one
such service.
Scott Fraser
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