Icoms are notorious for this because the normal mic element is a electret (condenser).
A Heil PR40 will require a pre-amp inline. I use this for a Heil HM10 dynamic.
It has 5 bands of EQ and ample mic gain adjustments, plug and play. The front 1/8 inch phone jack is for either a electret element or a
dynamic mic with a inline DC blocking cap. I have found that with this box that no compression is needed.
