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 completely separate 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.
The power supply for the X2.2 consists of a toroidal power transformer delivering an unregulated +/- 45 volts which is actively regulated before feeding passive filtering and powering the constant current sources which bias the gain stages. Each channel has its own regulation. The power supply noise reaching the circuit is on the order of one microvolt, and the little of that which gets through the circuit is rejected at the output in a balanced system. The relays and control systems are regulated independently, and all digital circuitry is isolated from the power supply.
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. The preamplifier is designed to run constantly, and will exhibit optimum measured performance within about 10 hours of turn-on.
The X2.2 consists of a single chassis.
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