I heard many times here that we need stable threshold tone. But when I increase the sensitivity up to 30 and get unstable tone and many other sounds I merely low down thresh tone volume to 0 and with these settings still have very good depth and high sensitivity to small objects hunting in silent mode with IM-12 getting only middle-high tones. It is extremely convenient in All metal as well ( with three metal tones ). No noise at all, good sounds only! What could be wrong here? Why it could not be the best for newbies as me... What I could miss here? Many thanks for any comment!