I have a Herbert not a VH4
Since i got my Herbert i noticed that the gain sensitivity off the amp is like no other amp i had before.
Using higher gain resulted in a thinner and compressed sound. After alot of fiddeling i found that using a lower gain setting and using more channel volume gave me a more open sound.
It was something getting used to, it felt like something was missing, but it made me understand more about equing and made me a far better player. Using less gain makes you hear more mistakes and forces you to play cleaner.
Ive also did the lower gain thing afterwords with engl's and soldano's, i had the same results, i got a ''Fatter and more open tone'' just find the sweet spot(just before you get more compression and fizzle, if im explaining it right)