Precision Power DCX 500.1 - Manual (Page 17)

ADVANCED INSTRUMENTATION INPUT
The Advanced Instrumentation Input has been incorporated from
the legendary
PrecisionPower TM 2500F1 . This circuit completely
isolates the chassis ground from the audio circuit of the amplifier
and reduces noise radiated into your signal cables by up to 40dB.
This is equivalent to a noise reduction of approximately one hundred
times what the noise level would be without this circuitry. It provides
all the benefits of a true balanced line without the need of any
special cables (see diagram below). This type of input works with
any conventional RCA cables.
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