most probably filter capacitors need check/replacement
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if this is a "mechanical" sound that comes from the amp itself and not through the speakers, it's not likely to be filter caps. Rather, it sounds like some screws may need tightening on the case or something similar. I think the DNA-1 likes to run at hi temps, which will cause heat sinks and possibly the transformer to generate heat . . . which cause expansion.
I second that you may have something loose. Check all screws, nuts and bolts, including the transformer mounting bolt(s). I once had an amp that made 2-3 rapid metallic clicks at every cold power-up. I traced the problem to an overtightened top cover screw. I had removed the top cover to re-bias the amp not long before the clicking started, which provided a clue that the noise was the result of something I had done.
The noise is caused by different rates of thermal expansion & contraction between the steel chassis and aluminum heat sinks. It is actually caused by the hardware being too tight, so if you carefully check the hardware to see that it is snug but not over-tight you should be able to eliminate the sound.