FIG. 4 MULTIPATH DISPLAY
LEVEL
The audio LEVEL of stereo signals is displayed as two
vertical columns on the screen ( Fig. 5). The height of
each column is determined by the power or amplitude of
the input signal. The calibration scale between the two
columns and the position of the POWER LEVEL knob
indicate the actual power of the signal. The nomenclature
on the recticle is shown in decibels (dB).
FIG. 5 LEVEL DISPLAY OF L & R CHANNEL
DUAL TRACE
When the DUAL TRACE buttons are pressed, the L
(Left) program and the R (Right) programs are seen as
separate traces on the screen. The left channel is the
upper trace; the right channel is the lower.
If only one button under DUAL TRACE is pressed (L
or R), the screen displays only the signal selected.
SWEEP and SWEEP FREQUENCY
Musical program material has many frequencies and it
may be displayed as a complex jumble of waves that are
difficult to view. By changing the timing, or sweep, of the
trace, the MPI 4 can lock onto any portion of the audio
spectrum. The result is a clear, easy-to-view wave that
remains stable on the screen. Use the SWEEP FREQUENCY
pushbuttons to provide a choice of low range frequencies
(20-200 Hz), mid-range frequencies (200-2000 Hz) and
high-range frequencies (2000-20,000 Hz). Use the SWEEP
control for fine tuning of the sweep within any range.
GAIN
The GAIN control operates only when preamplifier
signals are being displayed. The GAIN control varies the
vertical size of the image in all audio modes of operation.
When a signal of unknown strength is to be viewed, start
with the GAIN fully counterclockwise, then turn the con-
trol until the display reaches comfortable viewing size.
When the GAIN control is set to OFF, AC power is removed
from the MPI 4.
POWER LEVEL
The POWER LEVEL switch determines the full-scale
calibration in watts of signals displayed on the screen.
When the switch is turned, a red indicator illuminates
the selected power range of the WATTS column along
the right side of the screen ( Fig. 6). These ranges meas-
ure the actual power level of the power amplifier. (How
to use these ranges will be described in the next section.)
When the red indicator is opposite the topmost marking,
PREAMP, the screen displays the amplitude of the pre-
amplifier signal.
FIG.
6
INTENSITY
The INTENSITY control adjusts brightness of the trace
on the screen. For longest screen life, use the minimum,
comfortable viewing level.
The trace will disappear when there is no input signal
present. For extended cathode ray tube life a built-in auto-
matic intensity control extinguishes the trace during
non-signal periods to prevent a stationary spot from
burning a permanent mark in the screen surface.
VERTICAL
The VERTICAL control adjusts the up and down location
of the trace on the screen.
HORIZONTAL
The HORIZONTAL control adjusts the left to right loca-
tion of the trace on the screen.
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