Speco Technologies CAMMIC High-Impedance Line Level CAMMIC B&H
Variable Impedance Explained – Audient Help Desk
Simple Microphone (MIC) Amplifier Circuits
Low to High Impedance Adapter - MyPilotStore.com
Make High impedance preamplifier using a transistor | ElecCircuit.com
Piezo contact microphone hi-Z amplifier – low noise version – Richard Mudhar
Dynamic Mic Preamplifier Circuit
High-Z Input Preamps
Amazon.com: DLP Tactical Amplifier/Dynamic-to-Condenser Mic Adaptor Compatible with Low Impedance Peltor Comtac/MSA Sordin Headset to High Impedance PTT/Radio : Electronics
Make High impedance preamplifier using a transistor | ElecCircuit.com
4 Preamplifier circuits using transistors - Eleccircuit.com