Benchmark PRE420 Instruction Manual page 10

current low-capacitance input protection
circuits that protect the sensitive low-noise
input transistors from the worst-case
phantom-induced transients.
Large transients are produced when a
microphone is connected or disconnected
while phantom power is on. The worst
possible transients occur when a microphone
cable has an intermittent short to ground
from either pin 2 or pin 3. The PRE420 is
very well protected against both of the above.
For the protection of your microphones (and
your ears), we strongly recommend shutting
off phantom power several seconds before
connecting or disconnecting a microphone.
PRE420 Instruction Manual – rev. E Page 10