November 18, 2010 Rev 1.02
13
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 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 micro processor 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.
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-10 consists of a single chassis.
