Greg Hanks Design BA-660, Руководство по эксплуатации и обслуживанию

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BA660.doc 01/01/97 9 of 25
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+48 V
Switches phantom power on
and off at the Mic input
connector. Internal provision
is made for other voltages by
changing a zener diode.
Contact the manufacturer
for details. Always switch the
phantom power off when it
is not needed as it can
damage single ended signal
sources. The internal build
out resistors of 6k8 provide
for the IEC recommended
current limiting, but do not
provide adequate protection
against idiocy.
•
Input Selector
Switches between the mic
and line inputs as well as
establishing the gain
structure for the unit. The
extremely wide dynamic
range is in part made possible
by the judicious use of gain
setting relays that allow us to
manipulate the gain structure
by modification of the gain
stages and internal
attenuation.
•
Input overload LED
This LED lights when the
output of either the first or
second stage 34 dbv.
Occasional lighting still
allows an additional 6 db of
headroom!
•
Insert Bypass
Provided at the rear panel is
the output of the preamp
and the input to the gain cell.
These signals isolated from
the main signal path with
high voltage op-amps. When
the insert points are not
being used, we do not want
to degrade the purity of the
audio path with any solid
state devices so we sense the
insertion of a jack in either
the insert send or return
connector. When the system
is hard wired into an
installation, such as a rack in
a control room, we wanted
to offer the provision of
bypassing the insert silicon
from the front panel. When
there is no jack inserted in
the inserts, the signal is
automatically bypassed, and
the front panel switch
provides no function.
•
Input trim
This control provides
±
5 db
of trim for the front end
gain. Used in conjunction
with the input selector, you
set the input level to read
approximately "0" on the
Audio Meter, and then
establish your threshold
setting.
•
Phase reverse
Provides for 180
"
shift of
both the Mic and Line
Inputs. The Phase Reverse
switch point is post insertion
and Pre gain cell.
•
Meter zero
Trim pot for setting the "0"
Gain Reduction meter
position. This is done by