I've got a customer that has tried implementing a PZM10LL to make class audio recordings, driving a long shielded pair audio line back to a central control room (could be 200'-400' long). They are powering the mic locally at the source end. They have used conventional PZM 10's or 11's before and are hoping to streamline the installation. They found that the oscillation changed in strength when they switched from 12V to 24V power. If they place a transformer at each end the oscillation goes away. Is there a max capacitance spec for the cable that the LL version of the PZM's can drive, or a cable length limit?