The grounding on cheap DSO's and USB scopes can be risky (though the grounding on line powered scopes can be a problem also unless it is a differential scope, s

The grounding on cheap DSO's and USB scopes can be risky (though the grounding on line powered scopes can be a problem also unless it is a differential scope, sometimes it is a bad idea to clip an earth ground onto a circuit ground). With a USB scope you are counting on a inexpensive device to protect your valuable laptop computer and it can be inconvenient to use the computer for other purposes (you would have to stop a video render to use it as a scope for example). If you can afford it a low end Owon or Rigol is a much better investment. If it's just for fun with audio signals a software scope that uses a computers mic/line input may be good enough. If you want to view lissajous curves get a two channel analog scope (used on eBay or new starting around $200), most cheap digital scopes don't have a fast enough graphics capability to draw smooth lissajous curves. The frequency range of signals is often a deciding factor in scope choice, if what you want to view is 100MHz signals (or signals that include 100Mhz components/artifacts such as short spikes) then you need a scope that can handle that, if you just want to view audio signals any scope is probably good enough. The ability to capture and store signals can be useful to capturing one time events for analysis. The ability to store screenshots can be useful if you need to publish images of signals.