I have an audio interface called an m-audio profire 2626 (made sometime in the late 2000's) that's just a solid metal box that takes inputs form mics and 1/4 jacks - it only has a two prong plug-in which is currently plugged into a surge protector that has three prongs. Firstly, is this device safe without the three prong? Furthermore, I have other things plugged into the surge protector that are grounded. If I were to turn on one of the guitar amps (three prong) while I have earphones on my head connected to the audio interface (two prong) would this cause a difference in potential and possibly be a shock hazard?
The reason I ask is because last night I was recording something with the interface and I had my foot propped on the amp (classical style guitar) and I accidentally switched it on the bass amp (three prong) with my foot - the pop startled me and I did notice that the headphones sounded like static for a moment - to be honest not sure if I was just listening to the pop from the amp or if there was a little tiny shock. The fact that I could barely tell - I assume getting a bad shock would be much more obvious and painful. I don't want to find out.
Would it create a circuit if I touch something that's plugged into the same surge protector?
Should this interface have the three prong outlet like most other metal bodied appliances? It takes 12v.
I'm about 99% certain that the ground is done properly. This place was built somewhat recently, but I could get an outlet tester and double check.