Each input channel and th e three main outp u ts have an Ins ert
‘A’ gauge jack socket, which is a break point in the signal
path. It allows the signal to be taken out of the mixer,
through an external piece of equipment an d then back into the
mixer d ir ectly afte r it s or igin a l exit p o in t. Th e In ser t p o int is
normally bypassed by the ‘A’ gauge jack socket contacts, and
is only br ought int o operation when a p lug is insert ed.
Typica l uses wou ld in clude Effects Pr ocessor s, Limit ers,
additional Equalisers or Delay units. In addition, each
channel has a Direct output which may also be used to feed
external equipm ent.
The ter ms PRE and PO ST are often used in the context of
Inserts, Equalisers and A u xiliary Sends, and d escribe w hether
that facility is placed before (Pre) or after (Post) another
particular section. This is explained further in the detailed
descrip tion of facilit ies.
A mixer is often judged, amongst other factors, by the am ou nt
of Headroom available. This is a measure of the reserve
available to cope with sudden peaks in the inpu t signal,
without distortion caused by Clipping, when the signal
becomes so high tha t it wou ld exceed th e pow er su pp ly rail
voltages and is as a result limited. This commonly occurs
where gain set tings are incorrectly set or where sou rces are
improperly matched to th e m ixer inpu t. If the source signal is
too high, clipping and distortion results. If the signal is too
low it becomes masked by the background noise which is
present to some degree in all mixers. The diagram below
illustra tes this point .
If the signal levelis too low it may be masked
by the noise.
Signal
Noise
If the signallevel is too high, clipping distortion
may occur.
Clipped
Signal
Noise
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