engaged can damage speakers, headphones, and ears. Since passive
ribbon microphones or other transformer-coupled microphones are
particularly sensitive to phantom power, it is always recommended to
disengage phantom power before plugging and unplugging any ribbon
microphones.
The phantom current draw for active AEA ribbon mics is 7 milliamps.
IEC specifies P48 power which should be able to deliver 10 milliamps
per input. Some USB and battery-powered audio interfaces will not
deliver this. Please check the current values available on your unit to
ensure the best performance.
Wind Gusts
A second and equally important rule is never blow directly into any
microphone to test it. Not only does this force moisture and dirt into
the microphone, strong air movement also can stretch the ribbon
and while it may not break, it nonetheless could significantly degrade
the microphone’s performance. The ribbon in the A840 is protected
by multi-layered screens and grille cloths to provide superior wind
protection. Nonetheless, using it outdoors requires special care to
avoid wind which can damage the ribbon. Indoors, however, it is
also important to avoid serious air movement from stage curtains,
open windows, doors, or air-conditioning systems. High SPL sound
sources do not usually pose a problem because AEA’s active ribbon
microphones can handle 130 dB SPL or more without difficulty. It
is only those “explosive” sources that produce a strong blast of air,
such as the bass port on an electric guitar or bass amp, a guitar being
plugged (or unplugged) while the amp level is turned fully up, an on-
axis kick-drum (particularly with a port on the head), that are potentially
damaging. If you are unsure about how much wind is hitting the
microphone, place the back of your hand where the microphone is going
to be. If you can feel significant wind blasts, angle the microphone or
use a pop screen to avoid direct hits.
Tramp Iron
Minute iron particles, sometimes known as “tramp iron,” are common
within our environment. AEA ribbon microphones contain powerful
magnets that produce strong magnetic fields. These fields can attract
any ferric metal near the microphone that, if they are small enough, can
penetrate the outer screening and work their way inside the microphone.
Over time, this “tramp iron” can build up sufficiently in the magnetic gap
12
