29
The last remaining alternative would seem to be to insert the decoder
“within” a preamplifier by hooking it up in a tape loop. Unfortunately,
this set-up returns the Left and Right outputs of the decoder to the
preamplifier, where they can be inappropriately changed without
changing the Center and Surround outputs.
It is therefore
inappropriate to place surround sound decoders in a tape loop.
It would seem that there is no way to properly integrate a surround
sound processor with a preamplifier for a high quality, dual-purpose
system.
The Nº38S solves this dilemma by virtue of a specially designed
surround sound processor interface. When you select the “ssp” alias for
a particular input on the Nº38S, the output level and balance controls
are defeated and the preamplifier operates in unity gain mode,
passing through whatever signal enters that input without changing its
volume in any way. In fact, the display indicates that a line-level signal
is being “passed through” unchanged by showing “LINE” in the
display.
Thanks to this design innovation,
it is possible for the first time to
correctly integrate a surround sound processor with a preamplifier
,
sending the processor’s Left and Right outputs through the Nº38S (and
on to the power amplifier for the main front speakers). Since the
output level of these channels cannot be changed by the Nº38S while
in “ssp” mode, the preamplifier cannot corrupt the careful calibration
of the processor’s output levels. And since the video sources are fed
directly to the processor’s audio input(s) at a line level, input
calibration cannot be disturbed by the preamplifier.
Note: the Nº38S will not allow an input with an “ssp” alias to be
selected during initialization, since allowing a line level signal to
pass through unattenuated at start-up presents a potential
Surround sound
processors should not
be in a tape loop
Surround sound processors
and the Nº38S
Wiring Diagram with a
Surround Sound Processor
LF
RF
Ctr
RS
LS
Listening Room
MADRIGAL AUDIO LABORATORIES
R
display
intensity
monitor record select balance
inverted
polarity
mon
o
123456
standb
y
PREAMPLIFIER
Nº 38
mode
mute
video 1 video 2 video 3 video 4
Surround Sound Processor
Sub
Surround Power Amplifier
Center/Sub Power Amplifier
Main (Front) Power Amplifier
RFLF
RS
LS
Ctr
Sub
LF
RF
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