MACKIE PROFESSIONAL MIC/LINE MIXERS WITH FX AND USB I/O PROFX16 - Manual (Page 13)

Owner's Manual 13
8. INSERT
These unbalanced 1/4" jacks are for connecting
serial effects processors such as compressors,
equalizers, de-essers, or filters. The insert point is
after the gain control [9] and low cut filter [10],
but before the channel’s EQ [11-15] and level [23].
The channel signal can go out of the insert jack to
an external device, be processed and come back in
on the same insert jack.
To do this requires a standard insert cable that must be
wired thusly:
Tip = send (output to effects device)
Ring = return (input from effects device)
Sleeve = common ground
Insert jacks may be used as channel direct outputs;
post-gain, and pre-EQ. See the connector section on
page 27 (figure G) showing three ways to use insert
cables.
“U” like Unity gain
Mackie mixers have a “U” symbol on almost every level
control. It stands for “unity gain,” meaning no change in
signal level. The labels on the controls are measured in
decibels (dB), so you’ll know what you’re doing
level-wise if you choose to change a control’s settings.
9. GAIN
If you haven’t already, please read the level-setting
procedure on page 3.
The gain knobs adjust the input sensitivity of the mic
and line inputs. This allows signals from the outside
world to be adjusted to run through each channel at
optimal internal operating levels.
If the signal originates through the mic XLR jack,
there will be 0 dB of gain with the knob fully down,
ramping to 50 dB of gain fully up.
Through the 1⁄4" line input of channels 1-8 (ProFX16)
and channels 1-14 (ProFX22), there is 20 dB of
attenuation fully down and 30 dB of gain fully up, with
unity gain “U” at 12:00.
Through the 1⁄4" line input of channels 13/14 and
15/16 (ProFX16) and 19/20 and 21/22 (ProFX22), there
is 20 dB of attenuation fully down and 20 dB of gain fully
up, with unity gain “U” at 12:00.
This 20 dB of attenuation can be very handy when you
are inserting a hot signal, or when you want to add EQ
gain, or both. Without this “virtual pad,” there is more
chance of channel clipping.
10. LOW CUT Switch
All mono channels have a low-cut switch (often
referred to as a high-pass filter) that cuts bass
frequencies below 100 Hz at a rate of 18 dB per octave.
We recommend that you use low-cut on every
microphone application except kick drum, bass guitar,
or bassy synth patches. These aside, there isn’t much
down there that you want to hear, and filtering it out
makes the low stuff you do want much more crisp and
tasty. Not only that, but low-cut can help reduce the
possibility of feedback in live situations, and it helps to
conserve amplifier power.
Another way to consider low-cut’s function is
that it actually adds flexibility during live
performances. With the addition of low-cut,
you can safely use low equalization on vocals.
Many times, bass shelving EQ can really benefit voices.
Trouble is, adding low EQ also boosts stage rumble, mic
handling clunks and breath pops from way-down low.
Applying low-cut removes all those problems, so you can
add low EQ without blowing your subwoofers.
CHANNEL EQUALIZATION (EQ)
All ProFX mono channels have 3-band EQ with
shelving hi, peaking mid with adjustable mid
frequency and shelving low. The stereo channels have
a peaking mid EQ control in addition to the shelving hi
and shelving low EQ controls.
Shelving means that the circuitry boosts or cuts all
frequencies past the specified frequency. For example,
the low EQ boosts bass frequencies below 80 Hz and
continuing down to the lowest note you never heard.
Peaking means that certain frequencies form a “hill”
around the center frequency.
With too much EQ, you can really upset things.
We’ve designed a lot of boost and cut into
each equalizer circuit because we know that
everyone will occasionally need that. But if you max
the EQ on every channel, you’ll get mix mush. Equalize
subtly and use the left sides of the knobs (cut), as well
as the right (boost). If you find yourself repeatedly using
a lot of boost or cut, consider altering the sound source,
such as placing a mic differently, trying a different kind
of mic, a different vocalist, changing the strings, or
gargling.
“tip”
This plug connects to one of the
mixer’s Channel Insert jacks.
“ring”
tip
ring
sleeve
SEND to processor
RETURN from processor
(TRS plug)