Studio Technologies 750 - Manual (Page 37)

Model 750 User Guide Issue 3, May 1997
Studio Technologies, Inc. Page 37
Model 750
Faux VU Meters
In the spirit of George Washington (and
to make our mother proud of us) we have
to “tell the truth” and admit that while the
meters selected for the Model 750 are of
very good quality, they don’t meet the
specifications of a “true” VU meter. So
why was a less-than-perfect meter se-
lected for the Model 750? The answer is
easy and not surprising. While the Model
750’s existing meter is already quite ex-
pensive, being built in England by a top-
notch meter manufacturer, the cost for
a “true” VU meter is about five times as
much!
The technical difference between the
meter used on the Model 750 and a “true”
VU meter lies in the ballistic characteris-
tics, i.e. how the pointer accelerates and
decelerates in response to audio signals.
The Model 750’s meter pointer moves very
close to, but not exactly in the manner
required to be “perfect.”
For the Model 750 operator, the selected
meter provides a completely acceptable
indication of level. But as a technically-
oriented company, we wanted to “come
clean” about our actions. Too bad so
many other audio companies don’t tell
you that their “VU meters” are fakes—
many don’t even come close to meeting
the specs!
VU Meter Calibration
From the factory the VU meters are cali-
brated so that a +4dBu signal level, as
measured on main output 1, results in a
reading of 0 VU on the meters. (The meter
source button is set to the monitor (in)
position and the source is selected to
be main stereo.) However, it may be
observed that the meters may no longer
be precisely calibrated when the meter
source button is set to the main (out)
position. (In this position the main audio
bus is directly connected to the meters.)
A difference of up to 0.5dB from the cali-
brated value could be expected. This is
due to tolerance variations in the compo-
nents of the monitor circuitry. In reality,
only when a steady tone is present on the
main audio bus will this variation become
apparent. During actual operation it un-
likely to become a factor.