I’m looking at doing differential measurements of +/-15VDC power supplies to characterize ripple, noise, etc. I already have a QA472, QA403, and a Siglent scope. I see that the QA472 datasheet says that 15VDC can be sustained indefinitely, does that also apply to a -15VDC bias? Other options I have are some of the large caps that I have around already on the front end or using the XLR input with a dual BNC to XLR cable that I made for measuring rack equipment. That should already be AC-coupled because of the phantom power supply, right?