The pre-tested and pre-selected power transistors are next mounted onto the cooling devices. Special washers are used for this purpose. The transistors are tension-adjusted to guarantee that no under- or over-tightening occurs.

Under-tightening would result in a higher thermal resistance while over-tightening could shorten the expected lifetime of the transistor due to potential chip cracking. The power transistors are unique in that they can deliver extremely high currents and voltages (depending on type, up to 60A / 300V / 350W) at transfer speeds far higher than anything else available.

Thanks to this only few tightly selected transistors can handle the full duty. This allows unique circuit solutions as in most other high power amplifiers a large number of often cheap semiconductors must be used to achieve a half-way acceptable drive capability - a capability which is far below that of FM ACOUSTICS power amplifiers and is often insufficient to handle the actual requirements of the more demanding modern speakers loads.