I thought there was a sticky for ear crop care but there are a handful of vets in the country who do a good job on crops and their names are well known in dog world and on this forum. No shortage of "good vet for crops" threads here.
I think it wise to seek out the best vets available for crops in the doberman community than what "gizmo" is used, sort of goes w/the territory.
Having said that you'll read time & again that well bred dobermans already have had their ears done before you get them because most American breeders of any repute don't let their dogs go out in the world without cropped ears.