Stating the obvious, and preaching to the choir here, but...
that's because of their overly inflated cerebral appendages.
/
ducks and
runs
But at least that prevents the cranial-rectal inversion syndrome from which some others suffer.
To the OP, were all four amps and two mixers on one
circuit and you measured the
current for that
circuit? What were the actual "full volume" conditions? I'm not real surprised that you measured less draw than you might expect, however I am surprised at the 6A "full volume" number relative to the 5A idle number.
As David noted, real world audio signals are constantly varying and audio has to be looked at in terms of both peak and average levels, which then also affects the associated
power. For many types of music it is not unusual to have a 10-20dB
crest factor, which represents a peak
level 10 to 100 times the average
level, so it is quite possible to have high
level peaks and still have a much lower average
level. People are often surprised by how much of the time their 1,000W amp is outputting double digit Watts during typical use. However, if the peak
level remains the same then as the frequency of the peaks occurring increases or as the average
level increases, the
crest factor decreases and the
power required increases.
So that often leaves the dilemma of providing
power based on a 'worst case' scenario that may rarely apply or of making some assumptions and compromises knowing that they place some potential limits on the
system.