The newly improved ST9 Personal Studio is has been reduced to a size and weight approximately 1/4th that of the previous model. It is a tiny amplifier, small enough to fit into a shirt pocket, which offers a choice of clean or echo enhanced sound. It lets you hear your own playing at the volume you are accustomed to, to prevent any over-blowing. An Aux In is a direct line-in for playing along with CDs or other recordings. The ST9 Personal Studio may also be purchased separately for players who already own a Pickup Mute.