Another must try for fans of U2 and The Edge and another one of the boost pedals in his arsenal. Info from Boss about the long discontinued original:
The FA-1 is an incredibly small Field Effect Tramsistor (FET) based pre-amp. The controls are real easy. There's controls for volume, bass, treble and a low cut filter switch. The amplification is as much as 20 times (26dB) and it has an input impedance higher than any other device.