Any recommendations for a good cheap USB oscilloscope?

[NTL2009]

Be careful with those isolation transformers. If you unplug them at an unlucky point in the sinewave they'll make a transient that could be hard on your 'scope input... remove scope probe first.
that Amazon scope seem to have max input of 100 volts peak.

old jim

Good point. Thinking back, I don't think I unplugged or switched off the transformer while it was connected to the scope, I only switched the light or fan in the power strip.

 

[Windadct]

Well worth pointing out that Dave Jones on EEVBLOG -- has a lot of reviews and input on the whole scope issue... as reviews of entry level scopes...

 

[Tom.G]

Just a note: A 10X 'scope probe has a 9MegOhm resistor in it to make a 10x divider with the 1Meg 'scope input.

Sound cards often have an input impedance around 47k making a 10x 'scope probe a 192x divider. And you could always add a resistor in parallel with the audio input to get whatever divider ratio you need.

Cheers,
Tom