How many here own at least one oscilloscope for DIY audio work or even just electronics in general? Here's mine, a GW Instek GDS-1062A that I originally bought for working on college projects 7 years ago. The EEVblog box is an isolated high voltage probe, which I was testing its high frequency capabilities in the picture above by streaming a TV show through a Homeplug adapter. One audio related use for isolated/differential probes is probing the output of a balanced amplifier. However, I do a lot of power electronics work and that was the main reason I got it.