Instruction manual

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7
Voltage Selector A mains voltage selector switch is located beneath the top cover of the
unit, adjacent to the AC mains connector on the circuit board. With
primary AC power disconnected, slide the red actuator with a small
screwdriver so that the proper mains voltage (115 or 230) is visible.
You must always install an appropriate fuse, and should mark the rear-
panel voltage/fuse designation. It is factory practice to cross-out the
inappropriate marking with an indelible black marking pen. You can
remove this strikethrough with solvent to redesignate.
BE SURE that the mains voltage selector setting and pri-
mary fuse value are appropriate for the mains supply before
plugging the DAVID-II into the wall outlet.
Power Cord The detachable power cord supplied with the DAVID-II is fitted with a
North-American-standard male plug. The individual cord conductors
are supposed to be color-coded in accordance with CEE standards:
BROWN = AC “HOT” BLUE = AC NEUTRAL GRN/YEL = GROUND
If this turns out not to be the case, we offer our apologies (cord vendors
vary) and advise that U.S. color coding applies:
BLACK = AC “HOT” WHITE = AC NEUTRAL GREEN = GROUND
RADIO FREQUENCY INTERFERENCE ( R F I )
Location Although we have anticipated that the DAVID-II may be operated
adjacent to high-power transmitters, you should exercise care in
locating the unit away from abnormally high RF fields.
Ground Loops In some installations a mains frequency or RF ground loop may be
formed between the input or output cable shield grounds and the AC
power cord ground. Use of a “ground-lifting” AC adapter should
remedy the situation, though the chassis ultimately must be returned
to earth ground for safety. Generally, being screwed-down in the
equipment rack will satisfy this requirement.
LINE INPUT AND INPUT RANGE SELECTION
Input
Connections
The DAVID-II has electronically-balanced (transformerless) left and
right channel PROGRAM LINE INPUTS. These are brought out to a
screw-terminal barrier strip on the rear panel and include chassis
ground connections for cable shields. Please note that the screw-
terminal barrier block can be unplugged from the chassis! This makes
connection a bit easier and permits quicker removal of the DAVID-II
from the rack should maintenance ever be required.
Balanced Inputs
A balanced program audio feed to the DAVID-II will use both the +
and the – terminals, plus the associated G, for each of the two stereo
channels. Since these are “bridging” (high impedance) inputs, they