SoundCraft Spirit Live 4 - Manual (Page 7)

Each inp u t channel and the three m ain ou tp u ts have an Insert
‘A’ gau ge jack socket, w hich is a break p oint in the signal
p ath. It allow s the signal to be taken ou t of the m ixer,
throu gh an external p iece of equ ip m ent and then back into the
m ixer d irectly after its original exit p oint. The Insert p oint is
norm ally byp assed by the ‘A’ gau ge jack socket contacts, and
is only brou ght into op eration w hen a p lu g is inserted .
Typ ical u ses w ou ld inclu d e Effects Processors, Lim iters,
ad d itional Equ alisers or Delay u nits. In ad d ition, each
channel has a D irect ou tp u t w hich m ay also be u sed to feed
external equ ip m ent.
The term s PRE and POST are often u sed in the context of
Inserts, Equ alisers and Au xiliary Send s, and d escribe w hether
that facility is p laced before (Pre) or after (Post) another
p articu lar section. This is exp lained fu rther in the d etailed
d escrip tion of facilities.
A m ixer is often ju d ged , am ongst other factors, by the am ou nt
of Headroom available. This is a m easu re of the reserve
available to cop e w ith su d d en p eaks in the inp u t signal,
w ithou t d istortion cau sed by Clipping, w hen the signal
becom es so high that it w ou ld exceed the p ow er su p p ly rail
voltages and is as a resu lt lim ited . This com m only occu rs
w here gain settings are incorrectly set or w here sou rces are
im p rop erly m atched to the m ixer inp u t. If the sou rce signal is
too high, clip p ing and d istortion resu lts. If the signal is too
low it becom es m asked by the backgrou nd noise w hich is
p resent to som e d egree in all m ixers. The d iagram below
illu strates this p oint.
If the signal level is too low it may be masked
by the noise.
Signal Noise
If the signal level is too high, clipping distortion
may occur.
Clipped
Signal
Noise
Pa g e 5