MACKIE 1640 - Manual (Page 10)

10
ONYX 1640
ONYX 1640
Onyx 1640 Features
Channel Strips
All sixteen channels on the Onyx 1640
look alike and function identically with
the following exception: Channels 1
and 2 have high-impedance instrument
inputs in addition to the mic and line in-
puts so you can connect a guitar directly
to the mixer.
All the input and output connectors
(except for the headphone jack) are locat-
ed on the rear rotopod. We’ll take a look at
them after we explore the front panel.
1. 48V Phantom Power Switch
Most professional condenser micro-
phones require phantom power, which
is a low-current DC voltage delivered to
the microphone on pins 2 and 3 of the
XLR microphone connector. Push in the
48V button if your microphone needs
phantom power. An LED lights just
above the button to indicate that phan-
tom power is active on that channel.
Dynamic microphones, like Shure’s
SM57 and SM58, do not require phantom
power. However, phantom power will not
harm most dynamic microphones should
you accidentally plug one in while the
phantom power is turned on. Be careful
with older ribbon microphones. Check
the manual for your microphone to fi nd
out for sure whether or not phantom
power can damage it.
Note: Be sure the MAIN MIX fader
[46] is turned down when connecting
microphones to the MIC Inputs, espe-
cially when phantom power is turned on,
to prevent pops from getting through to
the speakers.
2. Low-Cut Switch
The Low-Cut switch, often referred to as a high-pass
fi lter, cuts bass frequencies below 75 Hz at a rate of 18 dB
per octave.
We recommend that you
use the Low-Cut fi lter on
every microphone appli-
cation except kick drum,
bass guitar, bassy synth
patches, or recordings of
earthquakes. These aside,
there isn’t much down
there that you want to
hear, and fi ltering it out makes the low stuff you do want
much more crisp and tasty. Not only that, but the Low-
Cut fi lter can help reduce the possibility of feedback in
live situations and it helps to conserve amplifi er power.
Another way to use the Low Cut fi lter
is in combination with the LOW EQ
on vocals during live performances.
Many times, bass shelving EQ can re-
ally benefi t voices. Trouble is, adding
LOW EQ also boosts stage rumble, mic
handling clunks, and breath pops. Low Cut removes all
those problems so you can add LOW EQ without losing a
woofer.
Here’s what the
combination of LOW EQ
and Low Cut looks like
in terms of frequency
curves.
3. MIC/HI-Z Switch (Channels 1 and 2)
Channels 1 and 2 have an extra button for switching
between the MIC and HI-Z inputs. When the button is out
(MIC), the XLR MIC input is used and the HI-Z input is
disconnected. When the button is pushed in (HI-Z), the
1/4" HI-Z input is used and the XLR MIC input is discon-
nected. The input stage of the HI-Z inputs is specially
designed for the high-impedance pickups on guitars.
Plugging a guitar into a lower-impedance
line input (like those on channels 3-16)
can result in the loss of high frequen-
cies, causing an unnatural and dull
sound. Normally, you must use a direct
box between a guitar and a mixer’s in-
put, which serves to convert the impedance of the guitar
from high to low. The HI-Z inputs on channels 1 and 2
make the need for a direct box unnecessary.
20 Hz 100 Hz 1k Hz 10k Hz 20k Hz
–15
–10
–5
0
+5
+10
+15
Low Cut
20 Hz 100 Hz 1k Hz 10k Hz 20k Hz
–15
–10
–5
0
+5
+10
+15
Low Cut with Low EQ Boosted
1
1
PAN
AUX
SEND
4
3
2
1
5
6
GAIN
FREQ
HIGH
12kHz
HIGH
MID
FREQ
LOW
MID
LOW
80Hz
EQ OUT
IN
8k 400
2k
2k 100
400
U
+15 -15
U
+15 -15
U
+15 -15
U
+15 -15
O O
O O MAX
O O MAX
O O MAX
O O MAX
O O MAX
L R
HI-Z
MIC
75Hz
18dB/OCT
+ 40dB
U
- 20dB
U
20
30
40
60
MAX
48V