It is an expensive mistake and really stinks. I hate when those happen. One time I was testing speakers with my high end gaming laptop. I disconnected the positive lead going from the amplifier to the speaker, but forgot to disconnect the negative. Hooked up dats and immediately blew my laptop. Yeah that wasn’t a good day. And to think that, at the time was also my editing computer. On a positive note, I ended up getting a new computer. On a negative note, I had to pay for it.