This is a project I used to assign to my Audio Electronics I students. I showed them how to use this probe along with an oscillator app on their phone and the RackAFX analyzer in line-in mode to setup their own little audio test systems in their dorm rooms – with the ability to probe and debug their analog audio projects at home – no need to run to the audio lab!
You can download the project document here: App Note Scope Probe
There are optional (but simple) modifications for added protection against over-voltage or over-current scenarios at the end of the document, though we never had any issues working on our low voltage audio devices. If you want to try to probe a tube amp (which is also dangerous!) you might want to add those protection circuits.
As with any hardware project posted here, design and use at your own risk!