Might just be general interference. Are you near a router, or monitor? Presumably you have a bass in that clip - what happens if you walk away from the head? Face away from it, like you would at the gig? Or rotate on the spot?
Not saying it's relevant in this case, but one thing Class D heads has done is made people forget how noisy environments can be. Class D heads - for all their sins (IMO) - don't really suffer from it.
I always cringe when I crank my stuff up to gig volume in the house, with loads of stuff in close proximity, but it's never a problem at the actual gig.