I have a few different tuners that I've used. And all of them seem to have issues locking on to exactly what note they are hearing from my low b string. Seems to bounce all over the place. I can't remember the make and model of my small one (I'll post it later) but Amplitube on my iPad and my Boss GT-10B multi effects board both also exhibit the same symptom. The note itself sounds good and strong on my amp and headphones, but the tuners just can't seem to lock into what note it is hearing. Is the low b just too low of a frequency for tuners to easily deal with?