24. Low Pass Filter
The mono output on the Helix Board 24 Universal includes a
Low Pass Filter (LPF) for removing high frequency sounds to
make the audio more appropriate for use with subwoofers. The
switch to the left turns the LPF on and off, and the rotary control
on the right allows users to adjust the cut-off frequency between
60Hz and 160Hz.
Channel Controls
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25. Gain Control
This controls the sensitivity of the input signal of the Line/
Microphone input of mono channels. The gain should be
adjusted to a level that allows the maximum use of the audio,
while still maintaining the quality of the feed. This can be
accomplished by adjusting it to a level that will ensure the peak
indicator doesn't light up, as specified in the channel set up
section.
26. Low Cut Filter (75 Hz)
This button, located on channels 1 through to 16, will activate a
high-pass filter that reduces all frequencies below 75 Hz at 18
dB per Octave, helping to remove any unwanted ground noise
or stage rumble.
27. High Frequency Control
This control is used to give a shelving boost or cut of ±15 dB to
high frequency (12 kHz) sounds. This will adjust the amount of
treble included in the audio of the channel, adding strength and
crispness to sounds such as guitars, cymbals, and synthesizers.
28. Middle Frequency Control
This control is used to provide a peaking style of boost and
cut to the level of middle frequency sounds at a range of ±15
dB. The Helix Board 24 Universal mixer also provides a sweep
control, allowing you to select a center frequency between
100 Hz and 8 kHz. Changing middle frequencies of an audio
feed can be rather difficult when used in a professional audio
mix, as it is usually more desirable to cut middle frequency
sounds rather than boost them, soothing overly harsh vocal and
instrument sounds in the audio.
29. Low Frequency Control
This control is used to give a shelving boost or cut of ±15 dB
to low frequency (80 Hz) sounds. This will adjust the amount
of bass included in the audio of the channel, and bring more
warmth and punch to drums and bass guitars.
30. AUX Controls
These four AUX controls alters the signal level that is being
sent to the auxiliary 1 to 4 mixing buses, the signal of which is
suitable for connecting stage monitors, allowing artists to listen
Helix Board 24 Universal
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to the music that is being played, or to fed to an external effect
processors. AUX 1 and 2 feature a Pre/Post button, which
alternates the feed to the AUX mixing bus between a post and
pre-fader feed. AUX 3, on the other hand, acts as an EFX send
for the internal effect processor, or simply as an Auxiliary output.
Both the AUX 3 (EFX) and AUX 4 controls are post fader and
are sent directly to the corresponding outputs.
31. Pre/Post Switch Selector
AUX 1 and 2 feature a Pre/Post button, which alternates the
feed to the AUX mixing bus between a post and pre-fader feed.
32. 5/6 Shift Button
This button changes the routing of the AUX 3 and 4 controls,
allowing the channel's signal to be directly output through the
AUX 5 and 6 outputs respectively.
33. Pan Controls
This alternates the degree or level of audio from that particular
channel that the left and right side of the main mix should
receive.
34. On Button and Indicator
This turns the channel on, allowing
the user to use the feed from the
channel's inputs to supply the
MAIN L/R, GROUP 1/2, GROUP
3/4, AUX and EFX buses (as
specified by the user, of course).
The corresponding indicator will
be illuminated when turned on.
35. Signal Indicator
This LED indicator shows when
the input level reaches -20 dBu,
basically showing when a signal
is received by the corresponding
channel.
36. 1-2, 3-4 and L-R Buttons
These handy buttons allow you to decide the audio path of the
corresponding channel. Pushing the "1/2" or "3/4" buttons allows
the signal to be sent to the Group 1/2 or 3/4 mixes respectively,
where the "L-R" allows it to be sent to the Main L/R mix.
37. Peak Indicator
This LED indicator will illuminate when the channel hits high
peaks, 6 dB before overload occurs. It is best to adjust the
channel level control so as to allow the PEAK indicator to light
up on regular intervals only. This will ensure a greater dynamic
range of audio. This indicator also doubles as a Solo indicator,
when the SOLO button is engaged.
38. Solo Button
The Solo button is pushed to allow the signal of the
corresponding channel to be sent to the Control Room / Phones
mixing bus (pre or post fader, depending on the properties
selected by the pre / post button, located below the solo level
control), for use with either headphones or studio monitors.
This button also allows for easier isolation of individual channel
signals, ensuring setting of the input gain or tracking of audio
by sound engineers is made simpler. The Peak indicator (above
the Solo button) also doubles as a Solo Indicator, illuminating
when the signal reaches high peaks.
39. Channel Level Control (Fader)
This 60 mm fader will alter the signal level that is sent from the
corresponding channel to the corresponding mixing buses.
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