Nothing here has a knob that massive on display but hey, it's what you do with it that counts.
So, technically, the biggest round volume knob on any of my boxes is that found in some Hitachi thing (pictured below) and it's not all that visible as it stays inside, attached to a conventional radial volume control pot and is driven by a dial cord connected with the slider on top of the set's aluminium exo-skeleton:
I'm not removing the left speaker fret and the speaker itself to measure but when I replaced the drive cord, that wheel appeared to be about 3 & 3/4" in diameter. Does it count if we can't see it?
