Using Piezo Pickups

When using an instrument with a piezo transducer (guitar, violin, double bass etc) run it into a load impedance of at least 10 Meg ohms. (most guitar amps are about 1 Meg & many active DI boxes are only 100K) The increase in level often massive increase in lows is amazing.

Passac preamps, for example, load the living daylights out of the piezo pickup & roll off most of the bottom end due to their 1 Meg input impedance.

A long lead on a piezo pickup won't roll the highs like it does on an electric guitar, the level just drops as cable length increases. (Same principle as a pad in a condenser mic)