SRS Labs SR445A, Руководство пользователя

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Power Supplies
The unit operates from a universal input/single floating output power supply. The power
supply can operate from AC mains with 90-132Vac or 175-264Vac between 47 & 63Hz
and outputs 18Vdc. An “active ground” is generated by the op amp U501 together with
Q500 & Q501 to generate ±9V. The op amp amplifies the midpoint voltage of the dc
power supply, which is at its non-inverting input, and either sources current (via Q501)
into the negative rail or draws current (via Q500) from the positive rail so that the
midpoint is at ground.
The ±9Vdc is regulated to ±5Vdc by U502 and U503. The ±5Vdc power supplies are
passively filtered by capacitors on the outputs of the regulators and by L/C filters for each
amplifier channel. Careful power supply filtering is important to reduce channel
crosstalk. The crosstalk from the output of channel 1 to the input of channel 2 is less than
-60dB (1:1000 of the amplitude) and peaks around 300MHz. The crosstalk from the
output of channel 2 to the input of channel 1 is less than -80dB (1:10,000 of the
amplitude) and occurs in a broad band between 180MHz and 360MHz.