Oscilloscopes - what specs to look for?


Hi,

I'm gonna get me an oscilloscope. I'm going to use it to mainly fiddle with home audio equipment, like hifi amps, and perhaps try to fix this and that other electrical appliance. 

What should I make sure I've got covered?

Some say 50Mhz is good, others 100Mhz. I've also realized memory depth is important, but what is enough? I see oscilloscopes can easily top the overall price of my hifi system if I'd really want to. 
128x128eyrepm
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If you have a computer, just get the software and a set of USB or Bluetooth oscilloscope probes and you’re all set. Way cheaper than a real electronic ‘scope. 
Ground on a scope is normally chassis ground (on all except fully isolated). Careful when you connect ground both for potential for a short and noise you didn't expect.
Even when scope is fully isolated there will be always some very small capacitance between BNC connector ground and the earth ground.  Because of that, probing any circuit that is not battery powered can deliver nonexistent noise, even if probe is shorted on the probed circuit ground.   It happens because there will be small current between probed circuit ground and scope's ground causing voltage drop on the probe's return.  Scope will "see" this voltage drop as a signal (since input is related to BNC connector GND and not the end of the probe GND).  It is just in case you wonder why scope shows anything (very small HF noise) when you touch circuit with shorted probe.