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Onyx 1620i
18. HI-Z SWITCH (Ch. 1 and 2 only)
Engage this switch if you want to connect guitars
directly to the 1/4" line inputs of channels 1 or 2.
Without this switch, you need to use a DI box first,
before connecting guitars. If these switches are not
pressed in, guitars will not sound good, particularly the
high frequency response.
Plugging a guitar into a lower-impedance
line-level input can result in the loss of high
frequencies, causing an unnatural and dull
sound. Normally, you must use a direct box
between a guitar and a mixer’s input, 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. However: The hi-z inputs are
unbalanced (when the switch is in), so if you’re doing a
live show and running a long cord between the
instrument and the mixer (say over 25 or 30 feet), it is
best to use a direct box with a balanced output to avoid
picking up noise over the length of the cord.
19. LOW CUT (Ch. 1–8 only)
The mono channels each have a low-cut switch (often
referred to as a high-pass filter) that cuts bass
frequencies below 75 Hz at a rate of 18 dB per octave.
The low cut switch affects both the mic and line
inputs.
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.
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