Analyzer Input Circuit
Figure 6-3 is a simplified diagram of one channel of the analyzer input.
The circuit is a true instrument-grade differential (balanced) input.
Both sides (pins 2 and 3) are loaded with 100 kΩ to ground, high
enough to bridge most audio circuits. The net gain from the input
connector to the analyzer proper is set by a combination of
compensated resistive attenuators (zero, 20 dB, or 40 dB attenuation)
and switchable-gain amplifiers (zero, +10 dB, +20 dB or +30 dB
gain). Both the attenuator setting and the amplifier gain are
microprocessor-controlled as part of the automatic ranging circuit, to
maintain the signal level fed to the remainder of the analyzer at an
optimum level for low noise and distortion.
6 Diagrams
Detailed Technical Diagrams Analyzer Input Circuit
6-6 Portable One Plus Access User's Manual
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