Distinctive sound.
Yes Guppy and the Aeroproducts equipped C130A's with T56-11 power plants and no "Low Speed Ground Idle", in RAAF service, had a quite different sound to the Hamilton Standard equipped aircraft.
Pity about you not being willing to share your C130 experience, not that I would ever be in a position to hire you. I was just interested in a comparison on type between yourself and me. It is unusual to learn of someone with experience as a Pilot, FE, mechanic and inspector at depot level on the one type. Personally, after about ten years on various other types of aircraft as a Ground Engineer, I had 2 years on the C130 at Senior NCO level as a Ground Engineer before transferring to FE. I accumulated a total of 4760 flight hours on type, predominately on the C130A, but also time on the C130E and H models. See Guppy, it's not hard to share, especially when it can be verified.