After adding an MI058, readings are wrong — higher noise floor, intermodulation, or wrong gain. How do I isolate it?
Work in three layers. First isolate the amplifier: bypass the MI058 and measure direct. If the reading returns to normal, the fault is in the amplifier or its bias. Second, check supply and grounding: ripple on the +12 V rail and ground loops both raise the noise floor, and the supply current should sit in the 100–150 mA range. Third, check level and spectrum: input overload appears as gain compression and intermodulation products, so lower the input level and repeat. With 40 dB of reverse isolation, output feedback should not be the cause — if it still misbehaves, inspect connectors and cables.
Key points
- Bypass the amplifier first; it separates amplifier faults from chain faults
- Check +12 V ripple and ground loops, which raise the noise floor
- Supply current should be within 100–150 mA
- Gain compression plus intermodulation means input overload — lower the level
- With 40 dB reverse isolation, suspect connectors and cable before the amplifier
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