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XP-20 Owner’s Manual
DISPLAY: The default setting for the display is “bright”, pressing
the “DISPLAY” button once changes the display to it’s “dim” or
“low intensity” setting, pressing the button a second time selects
“off ” for the display. When “off ” is selected any other control
function will cause the display to indicate product operational status
for approximately 7 seconds and then the display will once again
blank.
Pressing the “DISPLAY” button a third time cycles back to a “bright
display”.
We recommend the use of the balanced output mode where possible.
Balanced input to power-amplifiers will typically retain the character
of the input mode, but offers less distortion, less noise, more gain,
and more voltage swing, without compromising the sound.
With balanced operation, the common mode rejection of the preamp
reflects the intrinsic common mode rejection of the topology, the
matching of the gain devices, and the matching of the attenuator
channels. In this case we have been able to keep the total mismatch
to about .1%, for a common mode rejection of approximately -60
dB.
The input system of the preamplifier will exhibit full common mode
noise rejection with passive balanced sources, where the negative
input is connected to ground at the source through the appropriate
source impedance. This allows adaptation of unbalanced sources to
balanced operation with passive cable connections in a manner that
achieves the superior noise rejection of active balanced sources.
The use of a micro-controller allows all of the preamplifier functions
to be repeatable and accurately controlled. The microprocessor only
controls the functions of the preamplifier. At no time does any of
the input or output signal come into contact with the digital control
signals.
The digital circuits are powered by a power supply that is isolated
from the analog supply. Should it ever be necessary to update
the software that controls the functioning of the preamp only the
socketed micro-processor need be changed.
Rugged mechanical muting relays, which delay connection during
turn-on and shut off the output when insufficient power supply is
available to maintain regulation, guard the output of the preamplifier
and offer protection to the power-amplifier and loudspeakers.
The XP-20 consists of two chassis, shipped in a single box.