It’s only an air test did at home, I have taken advantage from the fact that wife isn’t here and my daughter doesn’t care! A low conductor below a high mineralized hematite stone to understand how and how much audio filter can improve detection on mineralized ground. Well, according to this test, audio filter works not only to amplify weaker deep signals and there is a big difference between audio filter 5 versus 1 and 2 but also 3-4 and obviously 0. Settings: prog.2 with disc 5, sensitivity 95, iron volume 5, audio response 5, 3 tones high square, square and PWM, silencer 2, no bottle cap and notch. In Pitch and with 2 only tones signal would have been stronger. 11”, 9” and 13” coils. Also big coil passed test with flying colors. I’m happy for the result . Look forward to go on the field!