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88 Appendix C: Application Notes
VeniceU
Operator Manual
channels will receive the same signal at the same time so, typically, when 16 channels
are summed together a gain of around 5dB to 8dB will be seen. It is important to leave
some headroom in the summing amplifiers so that they do not overload, should the
sum exceed the maximum level.
The effect of EQ
Channel equalisation should be used with care. Boosting or cutting equaliser bands can
make monitoring your actual input level very difficult. Excessive boosting of EQ (+15dB
is available on each band) will have the same effect as applying more gain to the input,
taking up valuable headroom. Consider backing off the channel gain when using large
amounts of boost (if you have to use large amounts of boost) to retain a sensible level
at the output.
Excessive EQ cut can have a similarly undesirable effect. If a large amount of signal is
cut in the equaliser section, gain may be used to ‘make up’ the level lost in the
equaliser. However, the input pre-amplifier still has the same amount of available
headroom. If gain, added to ‘make up’ the loss in the equaliser, exceeds the maximum
level into the microphone pre-amp then the channel won’t appear to be overloaded, but
the microphone pre-amp will. Turning off the equaliser will reveal the true story,
whereby the microphone pre-amp may be overloaded. It is worth considering whether
such large amounts of EQ cut is really required, or whether it is being used rather more
as a volume control (in which case the input gain could be set to a normal operating
level and the output adjusted on the channel fader).
You can monitor the level pre-EQ and post-EQ using the LED meter by switching
the EQ in and out during sound check.
Dynamic processing
When working with signals that are constantly at a high level the channel gain can
accommodate these signals with ease. When working with varying signals, such as
from a vocalist, it may be desirable to reduce the dynamic range of the signal so that
the loud parts aren’t so loud (and don’t overload your channel input) and the quiet bits
aren’t too quiet (so the signal to noise ratio would be increased).
Limiters and compressors have a similar function, which is to reduce the dynamic range
of a signal. The means by which they do this won’t be discussed here, but these
devices have the ability to reduce the level of loud signals automatically and also raise
the gain to ‘make up’ the level as desired. The channel gain can now be set with
adequate headroom to accommodate both loud and quiet signals, and the compressor
can reduce the dynamic range and ‘make up’ any reduction in level. By inserting such a
device into the channel’s insert point you have the ability to remove the guesswork
from setting your system gain.
However, there are still sources of potential problems. The VeniceU is able to operate
at levels up to +21dBu on both the insert send and return. If the maximum input level
of the compressor was less than +21dBu, it is possible to overload the input of the
compressor. The only way to resolve this situation would be to drop the channel input
gain so that the input level of the compressor was not being overloaded. However,
please note that the level returned from the compressor would also be lower
than +21dBu and excessive use of the compressor ‘make up’ gain would
overload the output of the compressor!