Agree with the great customer service (and value) from HSU which is often overlooked. On two different occasions I’ve been given a straight answer - one of which saved me some serious money. Previous owner of a ULS-15 and current owner of two VTF-3s.
Great service from HSU Research
Just FYI, my old HSU sub needed servicing. I emailed HSU (Steve) and got a quick response back, agreed to sent them just the amp itself and it was fixed and back in my hands in a week or so. Very fair price too. Good job HSU!