The pinpoint mode is very accurate on the 505. Usually when the circular lcd segments are completed, and the sound is the loudest/highest pitched the target is in the very center of the coil. If I'm not sure, I try to 'draw' a circle around the target with the coil if possible, in addition to the standard 'X' and see where the tone drops off and comes back as you circle the target. I'm sure you will get it down soon. HHAll I find are basic startup videos but none with actual videos on pinpointing.I'm getting better I'll have to admit but it would be nice to hear the tones when someone is right over a target.Im finding on my 505 the tones get slightly higher pitched.
Coily, I don't pay attention to audio when pinpointing, I just use the pinpoint mode and screen display. Once in pinpoint I move slowly in an x in til the pinpoint circle on the screen is to the farthest right. Once you get there the target will be dead center.