Issue 3, May 1997 Model 750 User Guide
Page 24 Studio Technologies, Inc.
Model 750
Changing the on/off status of the low-cut
filter will result in little or no noise being
added to the audio signal. While it is better
to set the filters button to the desired
position prior to being live, it can cer-
tainly be used at any time.
Phase Reverse
The button associated with the circle-
with-a-slash graphic symbol is used to
select the phase reverse function. (Many
people will know this as, and is techni-
cally, a polarity invert or polarity reverse
function.) In the normal (out) position, the
mic or line input signal maintains the same
polarity from input all the way through to
the main and AUX audio buses. In the
reverse (in) position, the signal is inverted
by 180 degrees. Changing from normal to
reverse, or vice-versa, will generally result
in little or no audio clicks or pops,
being generated, allowing the function to
be used during on-air situations.
This function can be useful in situations
where multiple microphones are present,
and signal cancellation problems occur.
The cancellation can be caused by mis-
wired interconnecting cables, faulty equip-
ment, or acoustic conditions related to
microphone placement. As signal cancel-
lation is not a trivial subject, we recom-
mend that you consult one of the many
fine audio textbooks that are available.
Well leave it to you to use the function as
required.
Status LED
A bi-color LED acts as a user-confidence
indication of the overall signal level in the
mic/line input channels circuitry. The LED
will light with the color green as a signal
present indicator, showing that the input
signal, along with the gain of the input
preamplifier, is at least 18dB below the
nominal internal operating level. The LED
will light with the color red as a peak
signal indicator, showing that the input
signal, along with gain of the preamplifier,
is within 6dB of the circuitrys maximum
level.
Rotary Controls
To address space considerations, the two
rotary controls associated with each mic/
line input channel share the same front
panel space; theyre known as concentric
pots. The inner control allows adjustment
of the preamplifier gain, the outer acts as
a pan-pot.
Level Control
The inner control is labeled LEVEL, and is
used to adjust the gain of the input pream-
plifier circuit. In the fully counterclockwise
position the preamplifier gain is set to its
minimum, and full attenuation is achieved.
This means that no signal continues on to
the next stage of the mic/line input circuitry
and, if configured, to the configurable
output on the back panel. As the level
control is rotated in the clockwise direction
the gain of the preamplifier increases.
Pan Pot
The outer control is labeled PAN, and
serves as a pan pot (panorama potentiom-
eter), controlling the routing of the mic/line
signal to the left and right channels of the
main and AUX audio buses. (Of course
the bus assignment buttons must be in the
on (in) position for the signal to actually be
connected to the buses.)
When the pan pot is in the fully counter-
clockwise position, signal is sent only to
the left mix buses; fully clockwise only to
the right. A mechanical detent provides
