Welcome, @danno266, glad you joined. Lurking - we have a lot of those too - but the participants - they are the cream of the crop, and the best - welcome, now you are one of us!
the "bunggg" noise you hear is interesting..., (if it's the same sound I hear in my amps)..., sometimes (I've heard) it can be reduced, other times, it's been suggested it's from the power inrush at turn-on, ... I have a pair of refreshed Carver Silver 9t monoblocks that makes that sound when I turn them on. The tech that did the work (member here) said not to worry...,
HOWEVER like said earlier by @Brian_at_HHH, you will be blown-away at the way your amp performs and sounds, when you get it back from @Nahash5150 at Nelion. Greg will for sure look into the "Bunggg" noise... 😉