Channel
instruction Manual
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
professional 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
microphone connected to the rear panel and simply
insert an instrument cable in to the front panel instru-
ment input when D.I. functions are required. You will
be able to acheive 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
precision low noise 6.81K
Ω
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 switched on can sometimes be dan-
gerous. Some microphones can be damaged by
power inrush. Good practice calls for switching off
the phantom power before changing or inserting a
microphone. Wait long enough to hear 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 phan-
tom 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
polarity (phase) of a mic signal. Vocalists monitor-
ing themselves 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 exapmple, 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.
Aphex Channel
