Aphex Channel - Manual (Page 8)

Page 8
3.1 USING THE MICROPHONE INPUT
The Channel is perfect for all types of microphones,
either powered or not. We encourage you to try every
mic you own with the Channel.
Many features of the Channel are standard with all pro-
fessional preamps - polarity - pad - etc. Some features
are unique and we hope you will fully exploit them.
3.2 USING THE INSTRUMENT INPUT
The Channel can also be used as a high quality direct
box. When an instrument cable is plugged in to the
Instrument input on the front panel, the rear panel XLR
input is bypassed. This allows the user to keep a micro-
phone connected to the rear panel and simply insert
an instrument cable in to the front panel instrument
input when D.I. functions are required. You will be able
to achieve proper input levels no matter what kind of
pickups are used. Single coil passive pickups will work
just as well as active humbuckers.
3.3 USING PHANTOM POWER
Active microphones that take power through the stan-
dard mic cable fall into a class called “phantom pow-
ered” mics. The power is called “phantom” because it
rides the mic cable invisibly, without interfering with
the audio signal carried on the same wires.
The industry standard phantom power source is posi-
tive 48 volts d.c. supplied to pins 2 and 3 through pre-
cision low noise 6.81KΩ resistors. You may note from
spec sheets that many mics rated for phantom power
actually run at something less than 48 volts. Don’t let
these specifications confuse you. They all run perfectly
well off the standard 48V phantom power source.
Plugging and Unplugging a microphone when phan-
tom power is on can sometimes be dangerous. Some
microphones can be damaged by power inrush. Switch
off the phantom power first. Wait for the mic go silent
before unplugging.
3.0 USING THE CHANNEL
FRONT PANEL VIEW
You should be aware of the shock hazard with the
phantom power system. Long, open mic cables that
are disconnected from the preamp while phantom is
on can hold a d.c. charge for long periods of time,
sometimes days, weeks or months. They will act as a
storage capacitor and you can get shocked most rudely
by holding the XLR plug and touching the pins inside.
Also beware of microphone patch bays that may carry
phantom voltage. Don’t hold the patch cord by the
metal parts, only the plastic shell.
CAUTION: Some ribbon mics will be damaged by
phantom power. Some ribbon mics require phantom
power and some just ignore it. Please consult your
manual before connecting a ribbon mic to the Channel.
3.4 USING THE POLARITY SWITCH
There will be times when you need to reverse the polar-
ity (phase) of a mic signal. Vocalists monitoring them-
selves on headphones will hear a different sound when
the phase is reversed. The reversed phase may sound
fuller and more truthful or hollow and far away. That is
because there is a cancellation of frequencies within the
ear when the external sound from the headphone mixes
with the sound directly conducted to the ear. “Flipping
the phase” can make the problem either more or less
noticeable.
Another time when phase reversing can be helpful is
when using multiple microphones on the same source.
For example, using two microphones on a guitar
speaker cabinet. You may get a “nasal” or hollow
effect when both mics are on. Changing the polarity
of one mic will often clear up the problem. It is always
worth the time to experiment with mic polarity.